Updated on 2022/05/17

写真a

 
AKIYAMA, Mitsuyoshi
 
Affiliation
Faculty of Science and Engineering, School of Creative Science and Engineering
Job title
Professor

Concurrent Post

  • Faculty of Science and Engineering   Graduate School of Creative Science and Engineering

Research Institute

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education

  •  
    -
    1997

    Tohoku University   Graduate School, Division of Engineering   Department of Civil and Environmental Engineering  

  •  
    -
    1995

    Tohoku University   Faculty of Engineering  

Degree

  • Tohoku University   Dr. Eng.

Research Experience

  • 2011.04
    -
     

    早稲田大学教授

  • 2007.04
    -
     

    東北大学准教授

  • 2004.04
    -
     

    東北大学助教授

  • 2001.10
    -
     

    東北大学講師

  • 1998.04
    -
     

    東北大学助手

  • 1997.04
    -
     

    日本工営株式会社東京事業部道路部

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Professional Memberships

  •  
     
     

    American Concrete Institute

  •  
     
     

    (社)日本コンクリート工学協会

  •  
     
     

    日本地震工学会

  •  
     
     

    IABSE

  •  
     
     

    IALCCE

  •  
     
     

    IABMAS

  •  
     
     

    ASCE

  •  
     
     

    (社)土木学会

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Research Areas

  • Structure engineering and earthquake engineering

Research Interests

  • earthquake-resistant structure, life-cycle analysis, reliability analysis

Papers

  • Effect of the interaction of corrosion pits among multiple tensile rebars on the reliability of RC structures: Experimental and numerical investigation

    Supasit Srivaranun, Mitsuyoshi Akiyama, Paolo Bocchini, Vasileios Christou, Dan M. Frangopol, Hiroyuki Fukushima, Keisuke Masuda

    Structural Safety   93  2021.11

     View Summary

    The deterioration of reinforced concrete (RC) structures due to chloride-induced corrosion is not spatially uniform because of the spatial variability related to material properties and environmental stressors. This variation has a substantial effect on the reliability of RC structures. However, few experimental studies have focused on the effect of the interaction of corrosion pits among tensile rebars on the reliability of RC structures. Therefore, in this paper, an experimental procedure that incorporates X-ray and digital image processing techniques was conducted on RC slab specimens subjected to accelerated corrosion. Using the experimental results, the parameter of the transverse correlation function of steel weight loss distributions was estimated to investigate how the corrosion pits in corroded rebars are correlated. Based on the experimentally obtained model parameters, the spatial steel weight loss distributions were simulated by spectral representation method. A three-dimensional (3D) nonlinear finite element (FE) analysis of RC structures with simulated steel weight loss distributions was conducted to obtain the ultimate bending capacity of RC structures. In an illustrative example, the effect of the transverse correlation among steel weight loss distributions of multiple tensile rebars on the failure probability of RC girders was quantified.

    DOI

  • Modelling method of fibre distribution in steel fibre reinforced concrete based on X-ray image recognition

    Yue Li, Xin Ruan, Mitsuyoshi Akiyama, Mingyang Zhang, Jiyu Xin, Sopokhem Lim

    Composites Part B: Engineering   223  2021.10

     View Summary

    The accurate and efficient simulation of steel fibre reinforced concrete (SFRC) is of great significance for its further application in civil engineering. Problems of existing modelling methods can be recognized as two points; (1) the integral model only simplified fibre contribution into the unified post-peak ductility in concrete element but cannot reflect the material variation caused by real fibre distribution, and (2) the separate model built the concrete matrix and fibre inclusions respectively, but the directly random fibre distributions still need to be refined based on the actual material. In this paper, based on the X-ray image recognition results from real SFRC material, a mathematical model of fibre distribution and orientation is proposed for SFRC simulation, and the detailed value distributions of geometrical parameters are optimized for convenience and accuracy of material modelling. In the geometrical extraction of near 4000 fibres from X-ray images, the whole comprehensive procedure of image processing, enhancement and recognition is presented with technologies like pixel semantic classification and Hough transform. With the proposed geometrical mathematical model, the modelling method that consists of multiple refined sampling is illustrated with mechanical applications. After the model verification by experimental comparison, the detailed contribution of steel fibre and the effect of fibre distribution refinement are discussed as well.

    DOI

  • A novel casting procedure for SFRC piles without shear reinforcement using the centrifugal forming technique to manipulate the fiber orientation and distribution

    Ramiz Ahmed Raju, Mitsuyoshi Akiyama, Sopokhem Lim, Tatsuya Kakegawa, Yuka Hosono

    Construction and Building Materials   303  2021.10

     View Summary

    The structural performance of steel fiber-reinforced concrete (SFRC) members primarily depends on the distribution and orientation of the fibers. Previous experimental studies revealed that the distribution and orientation of fibers are random and hardly controlled during the fabrication process. The centrifugal forming technique may improve the orientation and distribution of steel fibers in hollow circular SFRC piles and increase the shear strength of the piles. Accomplishing this task can lead to the possible replacement of shear reinforcements with steel fibers in piles, thereby improving the demanding productivity that is desired in the pile construction industry by saving considerable time and labor. This paper presents a novel experimental program to (a) develop the casting procedure for SFRC piles and (b) investigate the shear strength of SFRC piles without shear reinforcement compared to that of conventional reinforced concrete (RC) piles with shear reinforcement. With the aid of X-ray technology, different mix proportions and casting methods were investigated to determine the optimum procedure, which produced fiber distributions and orientations in SFRC piles superior to those of RC piles. The centrifugal forming method influenced the orientation of the fibers so that they were oriented in the shear stress direction (i.e., circumferential direction). The loading test demonstrated that the steel fibers effectively worked as shear reinforcement and that the shear capacity increased with the steel fiber content. Moreover, the SFRC piles exhibited stable crack propagation and improved post-cracking stiffness without severe concrete damage compared to that of the RC piles.

    DOI

  • Risk estimation of the disaster waste generated by both ground motion and tsunami due to the anticipated Nankai Trough earthquake

    Hiroki Ishibashi, Mitsuyoshi Akiyama, Takayuki Kojima, Koki Aoki, Shunichi Koshimura, Dan M. Frangopol

    Earthquake Engineering and Structural Dynamics   50 ( 8 ) 2134 - 2155  2021.07

     View Summary

    The amount of disaster waste is one of the most important performance indicators in quantifying the resilience of a community. In fact, disaster waste can have significant negative impacts on the environment in affected regions and hinder the postdisaster recovery process. Appropriate disaster waste management should be developed in Japan before the occurrence of the Nankai Trough earthquake. It is expected that the seismic and tsunami intensities caused by the anticipated Nankai Trough earthquake will be substantially larger than those caused by the 2011 Great East Japan earthquake. In this paper, a risk-based methodology is presented for estimating the amount of disaster waste generated by both the ground motions and the tsunami due to the anticipated Nankai Trough earthquake. First, Monte Carlo simulation-based probabilistic hazard analyses are performed to obtain seismic and tsunami hazard curves considering the uncertainty associated with fault movement along the Nankai Trough. Structural damage data associated with past earthquakes are used to develop seismic and tsunami fragility curves. The amount of disaster waste generated from a single structure is defined as the generation unit and is determined based on past disasters. Finally, with the aid of a geographic information system, the risk of disaster waste can be estimated using the hazard and fragility curves and the generation units. As an illustrative example, the risk curves and expected values associated with disaster waste in Mie Prefecture, Japan, are estimated based on the proposed framework.

    DOI

  • Probabilistic estimation of flexural loading capacity of existing RC structures based on observational corrosion-induced crack width distribution using machine learning

    Mingyang Zhang, Mitsuyoshi Akiyama, Mina Shintani, Jiyu Xin, Dan M. Frangopol

    Structural Safety   91  2021.07

     View Summary

    Corrosion-induced crack width can provide effective information on the deterioration level of in situ corroded reinforced concrete (RC) structures. However, the uncertainty associated with the relationship between corrosion-induced crack width and steel corrosion in RC structures is quite large. In this study, a probabilistic framework for estimating the structural capacity of corroded RC structures using the observational corrosion-induced crack width distribution and machine learning is proposed. Based on the experimental results of corroded RC beams, random field theory, and finite element (FE) analysis, artificial samples composed of corrosion-induced crack width and steel weight loss distributions over the RC beams are generated. Two machine learning-based models are then developed using these samples to estimate the steel weight loss distribution from the observational corrosion-induced crack distribution. Finally, a Monte Carlo-based FE analysis with the estimated steel weight loss distribution as the input data is conducted to obtain the probability density function (PDF) of the structural capacity of corroded RC beams. For illustrative purposes, the effect of observational corrosion-induced crack width distribution on the PDF of flexural capacity of an existing RC beam is investigated using the proposed framework. The results show that the proposed framework using a machine learning-based model is a reliable and computationally efficient approach for estimating the structural capacity of corroded RC members and demonstrates the potential for assessing the deterioration condition of existing RC structures based on the corrosion-induced crack width distribution.

    DOI

  • Spatial Variability of Rebar Corrosion and Performance Evaluation of Corroded RC Structures Using Probabilistic Analysis and Finite Element Method

    Mitsuyoshi Akiyama, Dan M. Frangopol, Mingyang Zhang

    Lecture Notes in Civil Engineering   153 LNCE   733 - 739  2021

     View Summary

    Corrosion of steel reinforcement is spatially distributed over RC structures due to several factors such as different environmental exposure, concrete quality and cover. Ignoring the effect of spatial variability is a drastic simplification for the prediction of the remaining service life of RC structures. Therefore, it is essential to identify the parameters influencing the spatial steel corrosion and structural performance of corroded RC structures. In this paper, an experimental research was conducted to study the effects of current density, concrete cover, rebar diameter, and fly ash on the spatial variability of steel weight loss, corrosion crack, and structural behavior of corroded RC beams using X-ray and digital image processing technique. The test results showed that low current density induced highly non-uniform corrosion associated with few large pits and cracks at certain locations while higher current density produced more uniform corrosion and cracks occurred over the whole beam. Gumbel distribution parameters were derived from the experimental data of steel weight loss to model spatial steel corrosion. A novel approach was established to assess the reliability of RC structures using finite element analysis and probabilistic simulation considering the spatial variability in steel weight loss. Using the Gumbel distribution parameters derived from the steel weight loss data associated with higher current density may underestimate the non-uniformity of corrosion distribution which can lead to an overestimation of the load capacity of corroded RC structures.

    DOI

  • Updating the reliability of existing rc structures in a marine environment incorporating spatial variations

    K. Masuda, S. Srivaranun, M. Akiyama

    Lecture Notes in Civil Engineering   101   1283 - 1288  2021

     View Summary

    A novel procedure for updating the reliability of existing reinforced concrete (RC) structures in a marine environment by incorporating spatial variations of steel weight loss is proposed. Since the properties of concrete and steel bars are uncertain, it is necessary to deal with the long-term structural performance based on probabilistic concepts and reliability-based methods. In this paper, epistemic uncertainties of material properties are updated using inspection results associated with steel weight loss prediction using Sequential Monte Carlo Simulation (SMCS). Possible distributions of steel weight loss over RC members are generated by a stochastic field method based on simple Kriging and inspection results at several observational points. Effect of the distance from the observational points on the reliability is discussed in an illustrative example.

    DOI

  • Risk estimation of bridges and bridge networks under seismic and subsequent tsunami hazards

    H. Ishibashi, T. Kojima, K. Nanami, M. Akiyama, D. M. Frangopol

    Lecture Notes in Civil Engineering   101   1189 - 1194  2021

     View Summary

    A procedure for estimating risk of road structures subjected to seismic ground motion and subsequent tsunami is proposed. In the 2011 Great East Japan earthquake, many bridges and embankments were severely damaged due to the strong ground motion and/or subsequent tsunami. The damage to these structures caused significant economic losses associated with the reconstruction and disruption of the road network. Given a limited budget, it is important to estimate the economic loss due to the damage to structures in road networks and determine the retrofitting prioritization for effective risk mitigation. In an illustrative example, the risk of road networks under both seismic and tsunami hazards caused by the anticipated Nankai Trough earthquake is estimated. The numerical results show that the retrofitting prioritization can be determined by comparing the risk of road networks.

    DOI

  • Reliability-based life-cycle cost design of asphalt pavement using artificial neural networks

    Jiyu Xin, Mitsuyoshi Akiyama, Dan M. Frangopol, Mingyang Zhang, Jianzhong Pei, Jiupeng Zhang

    Structure and Infrastructure Engineering   17 ( 6 ) 872 - 886  2021  [Refereed]

    Authorship:Corresponding author

     View Summary

    It is widely recognized that reliability-based optimization methodologies are rational and promising tools to perform the life-cycle management (LCM) of civil engineering structures. In order to realize the optimal design and maintenance of asphalt pavement, a comprehensive reliability-based optimization methodology considering the life-cycle cost (LCC) is proposed in this paper. Considering the powerful ability of Artificial Neural Networks (ANNs) to solve complex and nonlinear problems, ANNs are implemented to predict the performance of asphalt pavement based on the training data (i.e. structural, traffic, climatic, and performance parameters) selected from the Long-Term Pavement Performance (LTPP) program. Monte Carlo simulation (MCS) with Importance Sampling (IS) is conducted based on the obtained ANNs model to calculate the life-cycle reliability of asphalt pavement. Finally, the expected LCC including the initial construction cost, the preventive maintenance cost, inspection cost, users cost, and salvage value is minimized while maintaining a prescribed life-cycle reliability level for asphalt pavement. Several applications are presented to investigate the effects of traffic and climatic parameters on reliability-based optimum cost solution.

    DOI

  • Flexural behaviour of reinforced concrete beams repaired using a hybrid scheme with stainless steel rebars and CFRP sheets

    Md Abul Hasan, Mitsuyoshi Akiyama, Koya Kashiwagi, Keisuke Kojima, Long Peng

    Construction and Building Materials   265   120296 - 120296  2020.12  [Refereed]

    Authorship:Corresponding author

     View Summary

    The repair of corroded reinforced concrete (RC) structures is a critical issue for structural designers and managers because the repair cost significantly dominates the life-cycle cost. Moreover, in chloride-containing environments (e.g. coastal environments), RC structures repaired with conventional methods may corrode again since the ingress of chloride ions, water, and oxygen into the concrete will not be completely restrained. In this paper, a novel repair method for corroded RC beams using stainless steel (SS) rebars and externally bonded carbon-fibre-reinforced polymer (CFRP) sheets is proposed. The flexural behaviour of a group of RC beams repaired using the proposed method is experimentally investigated. The test variables include the longitudinal reinforcement types (i.e. carbon and SS), shear reinforcement configurations, and CFRP sheet wrapping schemes. Experimental results demonstrate that a carbon steel (CS) reinforcement can be replaced with an SS reinforcement to reduce future repair costs since there is no significant difference in the flexural behaviour of beams reinforced with CS and SS rebars. The effectiveness of CFRP sheet wrapping schemes on the flexural performances of SS-RC beams is approximately identical to that of CS-RC beams. In addition, the present paper discusses the serviceability and ultimate limit states of RC beams retrofitted with SS rebars and CFRP sheets based on the current design codes for ordinary RC beams strengthened using CFRP sheets. The predictions are in good agreement with the experimental results.

    DOI

  • Effect of the correlation of steel corrosion in the transverse direction between tensile rebars on the structural performance of RC beams

    Mingyang Zhang, Naoki Nishiya, Mitsuyoshi Akiyama, Sopokhem Lim, Keisuke Masuda

    Construction and Building Materials   264   120678 - 120678  2020.12  [Refereed]

    Authorship:Corresponding author

     View Summary

    Reinforcement corrosion is highly nonuniform and spatially distributed in reinforced concrete (RC) structures. Since RC members are reinforced with multiple rebars, corrosion of one rebar might affect another rebar in the transverse direction, thereby influencing the behavior of the structure. Hence, greater attention should be paid to studying the effects of the correlation of localized corrosion between adjacent rebars on the structural performance of RC members. In this paper, the effects of localized corrosion and the correlation of steel corrosion between tensile rebars on the structural performance of corroded RC beams were investigated through experiments and finite element (FE) analyses. The experimental results indicated that compared to the RC beams corroded over their entire length, the partially corroded RC beams with highly localized steel corrosion in the mid-span experienced large reductions in both loading capacity and ultimate deflection. Moreover, for beams with multiple rebars, the results showed that the beams with higher correlation coefficients of cross-sectional area loss between rebars had lower load and deflection capacities than the beams with lower correlation coefficients. The load–deflection responses of the beams with multiple rebars simulated by the 3D FE model were found to be in better agreement with the experimental results than those of the 2D FE model. Furthermore, a Monte Carlo simulation (MCS) was performed using a 3D FE model for two different cases: correlated and uncorrelated steel corrosion in the transverse direction of the RC beam. The results showed that a stronger correlation of steel cross-sectional area loss on different tensile rebars led to a larger variation in the load capacities of the corroded RC beams.

    DOI

  • Effects of concrete flow on the distribution and orientation of fibers and flexural behavior of steel fiber-reinforced self-compacting concrete beams

    Ramiz Ahmed Raju, Sopokhem Lim, Mitsuyoshi Akiyama, Takumi Kageyama

    Construction and Building Materials   262  2020.11  [Refereed]

     View Summary

    Several parameters during the fabrication process cause segregation and poor orientation of the fibers in steel fiber-reinforced concrete (SFRC) members. With its high flowability and compactability, self-compacting fiber-reinforced concrete (SCFRC) can be used as an alternative to conventional SFRC, as it exhibits improved orientation and lesser fiber segregation. This study aims to investigate (1) the effects of concrete type (i.e., SCFRC versus SFRC), fiber content, and specimen depth on the fiber distribution and orientation and (2) the structural performance of SCFRC and SFRC beams considering their fiber distribution and orientation using X-ray images. The X-ray images showed that owing to the high-flow properties, the SCFRC beams exhibited a lower fiber segregation and better fiber alignment than the SFRC beams. The bending test results demonstrated that the SCFRC beams exhibited better flexural performance than the SFRC beams owing to the improved distribution and orientation of the fibers. Moreover, a finite element (FE) analysis was performed to evaluate the structural performance of the beams considering the varying fiber distribution properties observed in the X-ray images. The FE method could differentiate the superior structural performance of the SCFRC beam from that of the SFRC beam.

    DOI

  • LCC-based identification of geographical locations suitable for using stainless steel rebars in reinforced concrete girder bridges

    Md Abul Hasan, Kekui Yan, Sopokhem Lim, Mitsuyoshi Akiyama, Dan M. Frangopol

    Structure and Infrastructure Engineering   16 ( 9 ) 1201 - 1227  2020.09  [Refereed]

     View Summary

    Reinforced concrete (RC) bridges under traffic loads and a severe airborne chloride environment require more frequent and intensive maintenance activities to preserve an adequate performance level. The use of stainless steel (SS) reinforcement in lieu of carbon steel (CS) reinforcement can be a promising alternative to avoid corrosion problems and reduce the maintenance cost. As the airborne chloride intensity depends on the meteorological condition and the distance from coastline, it is essential to determine the appropriate geographical locations where the use of SS rebar provides economic benefits. The main purpose of this paper is to present a novel approach for identifying the location of RC bridge suitable for SS rebar use considering the hazard intensity associated with the airborne chloride based on the probabilistic life-cycle cost (LCC) analysis. A novel probabilistic method for LCC estimation of RC bridge girders under traffic and airborne chloride hazards is established. In an illustrative example, the suitable location and critical distance for SS rebar application in RC bridges under different coastal environments in Japan are identified based on the proposed method. Sensitivity of LCC to four key parameters including discount rate of money, corrosion rate of SS rebar, concrete cover, and water-cement ratio is performed.

    DOI

  • Bidirectional shaking table tests of a low-cost friction sliding system with flat-inclined surfaces

    Miguel B. Brito, Mitsuyoshi Akiyama, Yoshitaka Ichikawa, Hiroki Yamaguchi, Riki Honda, Naomitsu Ishigaki

    Earthquake Engineering and Structural Dynamics   49 ( 8 ) 817 - 837  2020.07  [Refereed]

     View Summary

    A novel low-cost friction sliding system for bidirectional excitation is developed to improve the seismic performance of reinforced concrete (RC) bridge piers. The sliding system is a spherical prototype developed by combining a central flat surface with an inclined spherical segment, characterized by stable oscillation and a large reduction in response accelerations on the flat surface. The inclined part provides a restoring force that limits the residual displacements of the system. Conventional steel and concrete are employed to construct a flat-inclined spherical surface atop an RC pier. The seismic forces are dissipated through the frictions generated during the sliding movements; hence, the seismic resilience of bridges can be ensured with a low-cost design solution. The proposed system is fabricated utilizing a mold created by a three-dimensional printer, which facilitates the use of conventional concrete to construct spherical shapes. The concrete surface is lubricated with a resin material to prevent abrasion from multiple input ground motions. To demonstrate the effectiveness of the system, bidirectional shaking table tests are conducted in the longitudinal and transverse directions of a scaled bridge model. The effect of the inclination angle and the flat surface size is investigated. The results demonstrate a large decrease in response acceleration when the system exhibits circular sliding displacement. Furthermore, the inclination angle that generates the smallest residual displacement is identified experimentally.

    DOI

  • 強震動と津波ハザードの連続性を考慮した橋梁・盛土構造物の信頼性評価法の提案と南海トラフ地震を想定したケーススタデ

    石橋寛樹, 小島貴之, 秋山充良, 越村俊一

    土木学会論文集A1   76 ( 1 ) 41 - 60  2020.06  [Refereed]

    Authorship:Corresponding author

  • 南海トラフ地震により生じる津波災害廃棄物量のリスク評価

    小島貴之, 石橋寛樹, 秋山充良, 越村俊

    構造工学論文   66A   159 - 169  2020.03  [Refereed]

    Authorship:Corresponding author

  • Toward life-cycle reliability-, risk- and resilience-based design and assessment of bridges and bridge networks under independent and interacting hazards: emphasis on earthquake, tsunami and corrosion

    Mitsuyoshi Akiyama, Dan M. Frangopol, Hiroki Ishibashi

    Structure and Infrastructure Engineering   16 ( 1 ) 26 - 50  2020.01  [Refereed]

     View Summary

    After recent large earthquakes, field investigations confirmed that several bridges were severely damaged and collapsed not only due to the earthquake, as an independent hazard, but also to the subsequent tsunami, landslide or fault displacement. In addition, long-term material deterioration might have an important impact on seismic damage to bridges. Therefore, it is important to study both independent and interacting hazards and their effects on the reliability and risk of bridges and bridge networks. Although earthquake is still a dominant hazard to bridges in many earthquake-prone countries, a life-cycle reliability and risk approach has to consider both independent and interrelated hazards causing bridge failure. Such an approach is presented in this paper. In addition, issues related to life-cycle analysis, design, risk, resilience and management of bridges under earthquake and other hazards are discussed. Finally, the concepts and methods presented are illustrated on both single bridges and bridge networks.

    DOI

  • ROAD NETWORK RETROFITTING PRIORITIZATION UNDER SEISMIC AND TSUNAMI HAZARDS CAUSED BY THE ANTICIPATED NANKAI TROUGH EARTHQUAKE BASED ON THE PROBABILISTIC RISK AND RESILIENCE

    Hiroki ISHIBASHI, Takayuki KOJIMA, Mitsuyoshi AKIYAMA, Shunichi KOSHIMURA

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   76 ( 4 ) I_32 - I_46  2020

    DOI

  • FRAMEWORK FOR ESTIMATING THE RELIABILITY OF BRIDGES AND EMBANKMENTS UNDER BOTH SEISMIC AND TSUNAMI HAZARDS: A CASE STUDY OF THE ANTICIPATED NANKAI TROUGH EARTHQUAKE

    Hiroki ISHIBASHI, Takayuki KOJIMA, Mitsuyoshi AKIYAMA, Shunichi KOSHIMURA

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   76 ( 1 ) 41 - 60  2020

    DOI

  • Framework for estimating the risk and resilience of road networks with bridges and embankments under both seismic and tsunami hazards

    Hiroki Ishibashi, Mitsuyoshi Akiyama, Dan M. Frangopol, Shunichi Koshimura, Takayuki Kojima, Kengo Nanami

    Structure and Infrastructure Engineering   17 ( 4 ) 494 - 514  2020

     View Summary

    To develop disaster mitigation measures in coastal regions affected by earthquakes, it is important to consider the effects of both seismic and tsunami hazards on road structures and assess the social impacts associated with the economic loss and reduction in network functionality. In this paper, a risk- and resilience-based assessment framework is established for road networks under both seismic and tsunami hazards. In the proposed methodology, the risk and resilience are quantified by the economic loss and postdisaster functionality of road networks, respectively. Uncertainties associated with estimations of fault movement, hazard intensity and structural vulnerability are considered when estimating the failure probability using Monte Carlo simulation. Moreover, structural vulnerability against tsunamis is estimated considering the effects of ground motion-induced damage on the reduction in tsunami capacity. As an illustrative example, the road networks in two Japanese cities expected to be affected by the anticipated Nankai Trough earthquake, which would cause strong ground motions and a subsequent tsunami, are analyzed. Finally, the retrofitting prioritization for various structures is discussed based on the risk and resilience quantified as performance indicators for social impacts.

    DOI

  • Risk-, resilience-, and sustainability-informed assessment and management of civil infrastructure in a life-cycle context

    You Dong, Mitsuyoshi Akiyama, Dan M. Frangopol, Yiannis Tsompanakis

    Structure and Infrastructure Engineering   17 ( 4 ) 441 - 442  2020

    DOI

  • Reliability estimation of corroded RC structures based on spatial variability using experimental evidence, probabilistic analysis and finite element method

    Mingyang Zhang, Huijuan Song, Sopokhem Lim, Mitsuyoshi Akiyama, Dan M. Frangopol

    Engineering Structures   192   30 - 52  2019.08  [Refereed]

     View Summary

    Corrosion of steel reinforcement is spatially distributed over RC structures due to several factors such as different environmental exposure, concrete cover, and concrete quality, among others. Ignoring the effect of spatial variability is a drastic simplification for the prediction of the remaining service life of RC structures. Therefore, it is essential to identify the factors influencing the spatial steel corrosion and structural performance of corroded RC structures. In this paper, an experimental research is conducted to study the effects of main parameters (i.e. current density, concrete cover, rebar diameter, and fly ash)on the spatial variability associated with steel weight loss, corrosion crack, and structural behavior of accelerated-corrosion RC beams using X-ray radiography and digital image processing. The test results showed that low current density (Icorr ≤ 50 µA/cm2)induced highly non-uniform corrosion associated with few large pits and cracks at certain locations while higher current density produced more uniform corrosion and cracks over the beam length. Gumbel distribution parameters were derived from the steel weight loss data for modeling spatial steel corrosion. A novel approach was established to assess the reliability of RC structures using finite element (FE)analysis and probabilistic analysis considering the effects of modeled spatial variability of steel weight loss based on X-ray photographs. Using the Gumbel distribution parameters derived from the steel weight loss data associated with higher current density may underestimate the non-uniformity of corrosion distribution which can lead to an overestimation of the load capacity of corroded RC structures.

    DOI

  • Life-cycle reliability analysis of shield tunnels in coastal regions: emphasis on flexural performance of deteriorating segmental linings

    Zheng Shu He, Mitsuyoshi Akiyama, Chuan He, Dan M. Frangopol, Si Jin Liu

    Structure and Infrastructure Engineering   15 ( 7 ) 851 - 871  2019.07  [Refereed]

     View Summary

    In contrast to reinforced concrete (RC) structures on land, RC shield tunnels in coastal regions deteriorate rapidly after their construction because of the combined effects of multiple mechanical and environmental stressors. In this paper, by considering the coastal hazards associated with chloride and the impacts of hydrostatic pressure, a novel approach is presented to estimate the life-cycle structural performance of a shield tunnel that has undergone deterioration due to chloride-induced steel corrosion. Deterioration processes in segmental linings are investigated via corrosion-accelerated experiments on individual segments, and the combined effects of corrosive agents and loads are emphasized. Monte Carlo simulation is used to estimate the time-variant failure probability of shield tunnels in a marine environment. In an illustrative example, the effects of structural location, hydrostatic pressure and material properties on the life-cycle reliability of shield tunnels are investigated.

    DOI

  • A study on the design method for the material composition of small particle-size asphalt mixture for controlling cracks in asphalt pavement

    Jiyu Xin, Jianzhong Pei, Mitsuyoshi Akiyama, Rui Li, Jiupeng Zhang, Libo Shao

    Applied Sciences (Switzerland)   9 ( 10 )  2019.05  [Refereed]

     View Summary

    Generally, various kinds of cracks are the main type of distresses during the service period of asphalt pavements. To save maintenance costs and improve the crack resistance of asphalt pavements effectively, this paper presents a unique design method for the material composition of small particle-size (SPS) asphalt mixture for controlling cracks in asphalt pavement. First, Stone Mastic Asphalt (SMA)-II was designed as a basic gradation according to the A.N. Talbot curve and SMA-II-1, SMA-II-2 and SMA-II-3 were designed according to the Superpave mix design method, the Bailey method and the Particle interference theory, respectively. Second, based on Marshall test results, the optimal fiber content and optimal asphalt content of three gradations were determined. Then, the influence of the passing rate of 1.18-mm sieve and 0.075-mm sieve on the air voids of SMA-II and the influence of the filler-asphalt ratio on the performance of SMA-II were investigated, and an appropriate range of filler-asphalt ratio was obtained. Finally, a high-temperature performance test, a water stability test, and a skid resistance test demonstrate that the overall performance of SMA-II can satisfy the specifications. A low-temperature bend test and analysis of bending strain energy density show that SMA-II with a crumb rubber modifier and a polymer fiber has better crack resistance performance than SMA-I (SBS-modified mixture). Life-cycle cost analysis shows the economic advantage of SPS asphalt thin overlays over traditional AC-13 thin overlays.

    DOI

  • Shaking table tests of a reinforced concrete bridge pier with a low-cost sliding pendulum system

    Miguel B. Brito, Hiroki Ishibashi, Mitsuyoshi Akiyama

    Earthquake Engineering and Structural Dynamics   48 ( 3 ) 366 - 386  2019.03  [Refereed]

     View Summary

    After the occurrence of various destructive earthquakes in Japan, extensive efforts have been made to improve the seismic performance of bridges. Although improvements to the ductile capacities of reinforced concrete (RC) bridge piers have been developed over the past few decades, seismic resilience has not been adequately ensured. Simple ductile structures are not robust and exhibit a certain level of damage under extremely strong earthquakes, leading to large residual displacements and higher repair costs, which incur in societies with less-effective disaster response and recovery measures. To ensure the seismic resilience of bridges, it is necessary to continue developing the seismic design methodology of RC bridges by exploring new concepts while avoiding the use of expensive materials. Therefore, to maximize the postevent operability, a novel RC bridge pier with a low-cost sliding pendulum system is proposed. The seismic force is reduced as the upper component moves along a concave sliding surface atop the lower component of the RC bridge pier. No replaceable seismic devices are included to lengthen the natural period; only conventional concrete and steel are used to achieve low-cost design solutions. The seismic performance was evaluated through unidirectional shaking table tests. The experimental results demonstrated a reduction in the shear force transmitted to the substructure, and the residual displacement decreased by establishing an adequate radius of the sliding surface. Finally, a nonlinear dynamic analysis was performed to estimate the seismic response of the proposed RC bridge pier.

    DOI

  • Visualization of the fibre dispersion in the steel fibre reinforced concrete using X-ray image

    Ramiz Ahmed Raju, Sopokhem Lim, Takumi Kageyama, Mitsuyoshi Akiyama

    Proceedings of the fib Symposium 2019: Concrete - Innovations in Materials, Design and Structures     351 - 357  2019  [Refereed]

     View Summary

    Uniform distribution of fibres which are orientated parallel to the direction of tensile stress is essential to improve the structural performance of steel fibre reinforced concrete (SFRC) members. However, the fibre distribution in concrete structures is hardly uniform due to the effects of many parameters during the fabrication process (vibration, placing methods, concrete moulds, etc.) which can negatively affects their structural performance. The use of self-compacting concrete (SCC) instead of normal concrete can be a good alternative where the fibres can be aligned in the direction of flow without the use of vibration. This paper presents an effort for improving the structural performance of fibre-reinforced concrete members by utilizing the high-flowability and self-placability properties of SCC to achieve better distribution and orientation of fibres. In the experiment, the self-compacting fibre reinforced concrete (SCFRC) was flown into beams and the X-ray image was taken over the whole length of each specimen to investigate the effects of flow distance from the casting point on the distribution and orientation of fibres. In addition, other specimens were also fabricated using SFRC (with normal concrete). The bending tests were performed to observe the flexural performance of SCFRC and SFRC specimens. By the comparison of their structural performance, it was found that SCFRC ones provided better performance due to the more uniform distribution of fibres which were aligned in the flow direction of SCFRC.

  • Time-dependent structural reliability analysis of shield tunnels in coastal regions

    Z. He, M. Akiyama, C. He, D. M. Frangopol

    Life-Cycle Analysis and Assessment in Civil Engineering: Towards an Integrated Vision - Proceedings of the 6th International Symposium on Life-Cycle Civil Engineering, IALCCE 2018     1031 - 1038  2019  [Refereed]

     View Summary

    Deterioration of RC structures due to chloride-induced reinforcement corrosion is a common problem in an aggressive environment. Especially for shield tunnels in coastal regions, structures undergo a complex and rapid deteriorating process under the coupling effects of multiple mechanical and environmental stressors during their life-cycle, such as high hydrostatic pressure and aggressive agents. The very few existing studies on the deterioration processes of shield tunnels, especially considering the coupling effects, were not generally oriented to accurately assess the lifetime structural performance of these tunnels. In this paper, the chloride transport process in segmental linings with the impact of hydrostatic pressure is illustrated, two transport approaches of chloride are suggested, and the time to corrosion initiation is predicted. Finally, a Monte Carlo Simulation is used in conjunction with a time-dependent failure probability estimation associated with the deteriorated structural performance due to the steel corrosion.

  • Time-dependent structural performance analysis of RC slab exposed to chloride attack by incorporating spatial variability

    Supasit Srivaranun, Keisuke Masuda, Mitsuyoshi Akiyama, Dan M. Frangopol

    13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2019    2019  [Refereed]

     View Summary

    It is well recognized that the material properties of a reinforced concrete (RC) structure and its dimensions are random due to the spatial variability associated with workmanship, environment and other factors. This randomness causes spatially corrosion damages such as corrosion crack, cover spalling and steel corrosion. Therefore, it is of great importance to simulate deterioration processes of RC structures in a stochastic field context. In this paper, based on a probabilistic model for steel corrosion in RC structures, steel corrosion distributions over RC slab is estimated using 2D Gaussian stochastic fields. In an illustrative example, a time-dependent structural performance of RC slab represented by the stochastic field was estimated using 2D nonlinear finite element method.

  • Risk and resilience of civil infrastructure systems under extreme events

    Mitsuyoshi Akiyama, Dan M. Frangopol

    IABSE Symposium, Guimaraes 2019: Towards a Resilient Built Environment Risk and Asset Management - Report     8 - 19  2019  [Refereed]

     View Summary

    Recent large earthquakes in Japan including the 2011 Great East Japan earthquake and the 2016 Kumamoto earthquake caused not only damage and collapse of structures due to strong ground motions, but also washout of structures due to the subsequent giant tsunami and huge landslide. It is expected that the damage and the economic loss resulting from the anticipated Nankai Trough earthquake would be larger than those resulting from these two recent large earthquakes. Although the quantifications of risk and resilience associated with damage to structures and civil infrastructure systems under extreme events is still an important research topic in the structural engineering community, research studies on risk reduction and resilience enhancement in terms of structural control, restoration of structures and post-disaster debris management must be also developed. These research topics and studies are the main topic of this paper.

  • Reliability-based durability design of shield tunnels in coastal regions

    Zhengshu He, Mitsuyoshi Akiyama, Dan M. Frangopol

    13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2019    2019  [Refereed]

     View Summary

    In this paper, a reliability-based durability design method for shield tunnels in a marine environment is introduced. In this context, a method for integration of the coupling effects of chlorides and hydrostatic pressure into reliability-based durability design of shield tunnels in a marine environment is proposed. By using the proposed method, material parameters of RC segmental linings can be determined. The target reliability-based durability design level shall be satisfied during structural lifetime.

  • Modeling spatial variability of steel corrosion using Gumbel distribution

    Mingyang Zhang, Sopokhem Lim, Mitsuyoshi Akiyama, Dan M. Frangopol

    13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2019    2019  [Refereed]

     View Summary

    Performance of corrosion-affected RC structures depends on the spatial variability of steel corrosion of reinforcing bars. The effect of spatial variability of steel corrosion on the remaining service life of concrete structures is significant. In this paper, an experimental study was conducted to investigate the effect of current density on the spatial variability of steel corrosion. This variability is modeled using Gumbel distribution derived from experiments and incorporated with FE method to estimate the yield loading capacity of RC beams. The results show that using Gumbel distribution parameters derived from the specimens with high current density may lead to an overestimation of load capacity of corroded RC beams.

  • Life-cycle performance assessment of road network under multiple hazards

    Hiroki Ishibashi, Kengo Nanami, Takayuki Kojima, Yumi Kawai, Mitsuyoshi Akiyama, Dan M. Frangopol

    13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2019    2019  [Refereed]

     View Summary

    A procedure for estimating risk and resilience of road networks associated with bridges and embankments subjected to seismic ground motion and subsequent tsunami caused by the anticipated Nankai Trough earthquake is proposed. Since road networks play a crucial role for the transportation system after a natural disaster, it is important to identify the degradation of functionality and economic loss due to damage to structures in networks. In an illustrative example, risk and resilience of road networks in Mie-Prefecture, where the effects of Nankai Trough earthquake would be very intense, are estimated. The numerical results show that the retrofitting prioritization can be determined by comparing the risk and resilience of road networks.

  • Influences of current density on the spatial steel corrosion and reliability of corrosion-affected RC beams

    Sopokhem Lim, Mingyang Zhang, Mitsuyoshi Akiyama

    Proceedings of the fib Symposium 2019: Concrete - Innovations in Materials, Design and Structures     2091 - 2097  2019  [Refereed]

     View Summary

    Ignoring the effects of spatial variability of steel corrosion can lead to an error in the long-term performance assessment of RC structures. Recent research has been focusing on modelling spatial steel corrosion using experimental data from the corroded RC members by means of the impressed current method. However, researchers have applied a wide range of current density neglecting its effects on the spatial steel corrosion and the reliability of corrosion-affected RC beams. This paper aims to study effects of current density on the spatial steel corrosion and reliability of RC structural beam using finite element analysis. Three RC beams were corroded using current density of 50, 100, and 500 μA/cm . The spatial growth in steel weight loss in RC specimens was quantified at different corrosion levels using X-ray and image processing techniques. It was found that low current density of 50 μA/cm induced more non-uniform steel corrosion than higher levels of current density. Gumbel distribution parameters were derived from the experimental results and used to approximately model the spatial steel corrosion. An illustrative example was provided to study the effect of the modelled steel corrosion associated with low and high current densities on the reliability analysis of a structural RC beam. It was found that the failure probability of the RC beam estimated using the modelled spatial steel corrosion associated with small current density was higher than that associated with high current density. 2 2

  • Effect of recycled aggregate quality on the bond behavior and shear strength of RC members

    Thanapol Yanweerasak, Theang Meng Kea, Hiroki Ishibashi, Mitsuyoshi Akiyama

    Applied Sciences (Switzerland)   8 ( 11 )  2018.10  [Refereed]

     View Summary

    During the aggregate crushing process, natural aggregate and clinging mortar from existing concrete will inevitably produce small cracks and weak bonds between the aggregate and the existing cement mortar. The weaknesses of the existing cement mortar, adhered to a natural aggregate, negatively affect the properties of a recycled aggregate concrete, which prevents its application in reinforced concrete (RC) structures. Recycled aggregate can be classified into several categories, according to its physical and mechanical properties. The properties of concrete incorporated with the recycled aggregate of various qualities can be controlled, and the variability in its strength can also be reduced. This study aims to promote the application of recycled aggregate by investigating the effects of recycled aggregate quality (i.e., water absorption and the number of fine particles) classified by the Japanese Industrial Standards (JIS) on material properties, mechanical properties, and shear behavior of RC beams with recycled aggregate.

    DOI

  • Life-cycle reliability assessment of reinforced concrete bridges under multiple hazards

    Thanapol Yanweerasak, Withit Pansuk, Mitsuyoshi Akiyama, Dan M. Frangopol

    Structure and Infrastructure Engineering   14 ( 7 ) 1011 - 1024  2018.07  [Refereed]

     View Summary

    This paper proposes a novel probabilistic methodology for estimating the life-cycle reliability of existing reinforced concrete (RC) bridges under multiple hazards. The life-cycle reliability of an RC bridge pier under seismic and airborne chloride hazards is compared to that of a bridge girder under traffic and airborne chloride hazards. When conducting a life-cycle reliability assessment of existing RC bridges, observational data from inspections can provide the corrosion level in reinforcement steel. Random variables related with the prediction of time-variant steel weight loss can be updated based on the inspection results using Sequential Monte Carlo Simulation (SMCS). This paper presents a novel procedure for identifying the hazards that most threaten the structural safety of existing RC bridges, as well as the structural components with the lowest reliability when these bridges are exposed to multiple hazards. The proposed approach, using inspection results associated with steel weight loss, provides a rational reliability assessment framework that allows comparison between the life-cycle reliabilities of bridge components under multiple hazards, helping the prioritisation of maintenance actions. The effect of the number of inspection locations on the updated reliability is considered by incorporating the spatial steel corrosion distribution. An illustrative example is provided of applying the proposed life-cyle reliability assessment to a hypothetical RC bridge under multiple hazards.

    DOI

  • Structural behavior prediction of SFRC beams by a novel integrated approach of X-ray imaging and finite element method

    Sopokhem Lim, Ramiz Ahmed Raju, Mitsuhiro Matsuda, Takehiro Okamoto, Mitsuyoshi Akiyama

    Construction and Building Materials   170   347 - 365  2018.05  [Refereed]

     View Summary

    Several studies have revealed that the fiber distribution is usually not uniform since many parameters during the fabrication process cause different fiber distributions and orientations within individual steel fiber-reinforced concrete (SFRC) members. This phenomenon results in large scattering in the post-cracking flexural responses among the material characterization specimens. Consequently, when estimating the flexural behavior of SFRC beams, conflicting results are often obtained using only a single constitutive stress-crack opening laws to characterize the material behavior in tension without considering the different fiber distributions and orientations. In this paper, a novel integrated approach is established to estimate the flexural behavior of SFRC beams using both a finite element (FE) method and X-ray imaging. In the prediction approach, a parameter that can be determined using the measured fiber distribution properties from an X-ray image is proposed to consider the variability of the fiber dispersion in each SFRC member. A method is presented for deducing the constitutive stress-crack opening laws using an FE analysis and the proposed parameter from X-ray images. In the numerical FE method, the variability of the fiber dispersion of the individual SFRC beams is determined by identifying the stress-strain relation in each mesh based on the proposed parameter from the X-ray images. The FE method provides better prediction results of the loading capacity for the SFRC beams.

    DOI

  • Seismic performance evaluation of bridge pier with friction pendulum isolation system

    B. Brito, T. Seto, Y. Ichikawa, N. Ishigaki, M. Suezaki, M. Akiyama

    11th National Conference on Earthquake Engineering 2018, NCEE 2018: Integrating Science, Engineering, and Policy   9   5760 - 5764  2018

     View Summary

    After the Great Hanshin Kobe Earthquake (1995), extensive effort for improving the seismic performance of bridges in the Japanese engineering community have been carried out. Although, isolation system has become effective to ensure the seismic resilience of bridge structures, high axial load and large displacements under strong ground motions are not well understood; moreover, during Tohoku Earthquake (2011) and Kumamoto Earthquake (2016), some damages of laminated rubber bearing were observed. Undoubtedly, it is necessary to continue developing the isolation systems by exploring new concepts. In this study, seismic performance evaluation of a novel system to isolate the superstructure by forming a concave sliding surface on the top of the concrete bridge pier; is experimentally conducted. Any seismic devices are not included for lengthening the system to a longer natural period, and based on the principle of pendulum the seismic energy can be dissipated through the frictional force. Proposed Friction Pendulum Isolation System (FPIS) possess re-centering capability while sliding toward the initial position, and large displacement can be enhanced. The results exhibited shear force-displacement relationship with a smooth behavior in the longitudinal direction; furthermore, the longitudinal and transverse direction depicted an appealing circular displacement orbit.

  • Life-cycle reliability of bridges under independent and interacting hazards

    Mitsuyoshi Akiyama, Dan M. Frangopol

    Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges - Proceedings of the 9th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2018     16 - 35  2018  [Refereed]

     View Summary

    After recent large earthquakes, field investigations confirmed that several bridges were severely damaged and collapsed not only due to the earthquake, as an independent hazard, but also to the subsequent tsunami, landslide or fault displacement. In addition, material deterioration might cause further seismic damage to bridges. Therefore, it is important to study both independent and interacting hazards and their effects on the reliability of bridge and bridge networks. Although earthquake is still a dominant hazard to bridges in many earthquake-prone countries, a life-cycle reliability approach has to consider both independent and interrelated hazards causing bridge failure. Such an approach is presented in this keynote paper. In addition, issues related to life-cycle analysis, design, risk, resilience and management of bridges under earthquake and other hazards are discussed. Finally, the concepts and methods presented are illustrated on both single bridges and bridge networks.

  • Life cycle cost management of concrete structures

    José Matos, Anders Solgaard, Poul Linneberg, Mauricio Sanchez Silva, Alfred Strauss, Irina Stipanovic, Joan Casas, Snezana Masovic, Colin Caprani, Drahomir Novak, Mitsuyoshi Akiyama

    IABSE Conference, Copenhagen 2018: Engineering the Past, to Meet the Needs of the Future - Report     130 - 136  2018  [Refereed]

     View Summary

    Tools, guidelines and standards for assessment of Life Cycle Cost (LCC) of built environment e.g. buildings, infrastructure assets etc. have gained impact over the past years. Owner and operator application of tools, guidelines and standards enhances optimization of operation and maintenance with due respect to their budgets. In order to aid owners, operators and their designers, a task group under fib has been established to prepare a state-of-the-art report regarding LCC analyses of concrete assets. The state-of-the-art report contains a description of existing LCC standards and guidelines, their applicability, the definition of different cost elements, and the treatment of uncertain information in a reliability or risk based framework, etc. providing the reader with background information and methodology for preparation of such analysis. Moreover, the report contains case studies, presenting the applicability of the LCC analysis methodology.

  • Effects of current density on the spatial variability associated with steel corrosion and flexural behavior of corroded RC beams

    S. Lim, H. Song, M. Akiyama, D. M. Frangopol

    Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges - Proceedings of the 9th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2018     1024 - 1028  2018  [Refereed]

     View Summary

    Since structural performance of corroded RC members primarily depends on localized corrosion damages on their reinforcements, modelling the spatial steel corrosion is important for the long-term performance assessment of RC structures. To achieve this purpose, there is a need to study the time-variant spatial distribution of steel corrosion. The impressed current technique by means of applying current density has been widely used to investigate the effect of steel corrosion on the structural capacity deterioration. It was reported that current density has great influence on the propagation of average crack width, steel corrosion, and structural behavior of RC members. However, the study of the effect of current density on the spatial variability of corrosion and cracking is scarce. Therefore, the main objective of this paper is to study, using X-ray and digital image processing techniques, the effects of current density on the spatial steel corrosion and corrosion cracking of corroded RC beams.

  • Effect of different steel weight loss distributions on the life-cycle reliability of PC girders

    N. Nishiya, H. Fukushima, A. Sakurai, M. Akiyama, P. Bocchini, D. M. Frangopol

    Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges - Proceedings of the 9th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2018     1001 - 1006  2018  [Refereed]

     View Summary

    In this paper, the time-dependent reliability of PC girders in a marine environment is estimated considering the spatial variability of steel weight loss. Non-linear finite element (FE) analysis of aging PC girders is performed. Spatial variation of steel weight loss represented by uniform, Gaussian and non-Gaussian stochastic fields is included in the FE modelling. To obtain the relationship between input parameters and computational results from FE analysis, the response surface method is used for reducing the time required to repeat the structural analysis. The life-cycle reliability outcomes associated with three different models for the steel weight loss distribution are compared and discussed in an illustrative example. The authors would like to acknowledge Mr. Vasileios Christou for his help during the development of the random simulation algorithm.

  • Reliability-based durability design and service life assessment of reinforced concrete deck slab of jetty structures

    Mitsuyoshi Akiyama, Dan M. Frangopol, Koshin Takenaka

    Structure and Infrastructure Engineering   13 ( 4 ) 468 - 477  2017.04  [Refereed]

     View Summary

    Reinforced concrete (RC) structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. Since the RC deck slabs of jetty structures are exposed to a very aggressive environment, higher deterioration rates can develop. In this paper, a reliability-based durability design and service life assessment of RC jetty structures are presented. For new RC jetty structures, the concrete quality and concrete cover necessary to prevent the chloride-induced reinforcement corrosion causing the deterioration of structural performance during the whole lifetime could be determined. Based on the airborne chloride hazard depending on the vertical distance from the sea level surface to the RC deck slab, the probability associated with the steel corrosion initiation is estimated. The water to cement ratio and concrete cover to satisfy the target reliability level are provided. For evaluating the service life of existing structures, the condition state based on the visual inspection of RC structure can be provided. The deterioration process of the RC jetty structure can be modelled as a Markov process. Therefore, the transition probability matrix at time t after construction can be updated by visual inspection results. A procedure to update the transition probability matrix by the Sequential Monte Carlo Simulation method is indicated. In an illustrative example, the effect of the updating on the life-cycle reliability estimate of existing RC deck slab in a jetty structure subjected to the chloride attack is presented.

    DOI

  • Life-cycle of structural systems: design, assessment, maintenance and management

    Hitoshi Furuta, Mitsuyoshi Akiyama

    Structure and Infrastructure Engineering   13 ( 1 ) 1 - 1  2017.01  [Refereed]

    DOI

  • Experimental investigation of the spatial variability of the steel weight loss and corrosion cracking of reinforced concrete members: novel X-ray and digital image processing techniques

    Sopokhem Lim, Mitsuyoshi Akiyama, Dan M. Frangopol, Haitao Jiang

    Structure and Infrastructure Engineering   13 ( 1 ) 118 - 134  2017.01  [Refereed]

     View Summary

    The material properties of concrete structures and their structural dimensions are known to be random due to the spatial variability associated with workmanship and various other factors. This randomness produces spatially variable corrosion damages, such as steel weight loss and corrosion cracks. The structural capacity of reinforced concrete (RC) members strongly depends on the local conditions of their reinforcements. Modelling the spatial variability of steel corrosion is important, but steel corrosion in RC members can only be observed after severely damaging the concrete members. To understand the steel corrosion growth process and the change in the spatial variability of steel corrosion with time, continuous monitoring is necessary. In this study, X-ray photography is applied to observe steel corrosion in RC beams. The steel weight loss is estimated by the digital image processing of the X-ray photograms. The non-uniform distribution of steel weight loss along rebars inside RC beams determined using X-ray radiography and its correlation with longitudinal crack widths are experimentally investigated.

    DOI

  • Life-cycle reliability assessment of corroded bridges under multiple hazards

    T. Yanweerasak, R. Takemoto, M. Akiyama, D. M. Frangopol

    Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016     420 - 426  2017  [Refereed]

     View Summary

    This paper presents a probabilistic framework for the life-cycle reliability assessment of existing bridges under multiple hazards. The life-cycle reliability of a bridge girder under traffic and airborne chloride hazards is compared with that of a bridge pier under seismic and airborne chloride hazards. When predicting the life-cycle reliability of existing bridges, observational data from inspection could be used to estimate the current material corrosion level. Random variables associated with the prediction of time-variant steel weight loss are updated by using Sequential Monte Carlo Simulation (SMCS). The life-cycle reliability of two bridge components under various hazards and inspection results are discussed in an illustrative example.

  • Life cycle cost, as a tool for decision making on concrete infrastructures

    José Matos, Anders Solgaard, Carlos Santos, Mauricio Sanchez Silva, Poul Linneberg, Alfred Strauss, Joan Casas, Colin Caprani, Mitsuyoshi Akiyama

    High Tech Concrete: Where Technology and Engineering Meet - Proceedings of the 2017 fib Symposium     1832 - 1839  2017  [Refereed]

     View Summary

    The use of Life Cycle Cost (LCC) tools in civil engineering is increasing, due to the need of infrastructure owners and operators to guarantee their assets maximum performance with an optimized budget. By considering these tools it will be possible to manage assets along their lifetime in a more sustainable and efficient way. Due to this reason, it was recently constituted a Task Group on fib to deal with existing LCC tools for concrete infrastructures. This paper gives an introduction to these tools, with a special emphasis to the added-value of LCC, and to the main contents of the fib TG 8.4 state-of-art technical report. This covers a description of existing LCC standards and guidelines, their applicability, the definition of different cost elements, the incorporation of risk in the analysis, etc.

    DOI

  • Assessment of the structural behavior of corrosion-affected rc beams: Experimental study and modeling

    S. Lim, M. Akiyama, D. M. Frangopol

    Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016     379 - 384  2017  [Refereed]

     View Summary

    Structural performance of deteriorated reinforced concrete (RC) members depends on the magnitude and location of steel corrosion. Finite element (FE) method has been applied to the structural performance assessment of corroded RC members; however, the difficulty in quantifying cross-sectional area of rebar embedded into the concrete has been reported as a main challenge for conducting the FE analysis precisely. The two main objectives of this paper are to: (1) experimentally investigate the effects of spatial variability associated with steel corrosion on the structural behavior of a corroded RC beam and (2) establish a FE numerical modeling to assess the structural performance of corroded RC beams. In the experimental study, the spatial variability associated with the steel weight loss over the RC beam is quantified using X-ray and digital image processing techniques. This experimental result is used as input data for the FE analysis. The proposed model provides good agreement with the test results.

  • SEISMIC DESIGN FOR “ANTI-CATASTROPHE” — A STUDY ON THE IMPLEMENTATION AS DESIGN CODES —

    HONDA Riki, AKIYAMA Mitsuyoshi, NOZU Atsushi, TAKAHASHI Yoshikazu, KATAOKA Shojiro, MURONO Yoshitaka

    Journal of JSCE   5 ( 1 ) 346 - 356  2017

     View Summary

     This paper presents a design concept of “anti-catastrophe” and proposes a framework of seismic design code for that concept. It proposes that the domain to be considered in the design should be extended in terms of three dimensions: phase, time, and space. We discuss the conditions required for the implementation of “anti-catastrophe”-oriented design. Since concepts of “anti-catastrophe”-oriented design is significantly different from that of conventional design, it is proposed to introduce “Category of Design” (CoD). We then present a design framework which consists of five stages. We also discuss institutional conditions required for this new design codes from the viewpoint of risk governance.

    CiNii

  • Life-cycle reliability assessment of corroded bridges under multiple hazards

    Yanweerasak, T, Takemoto, R, Akiyama, M, Frangopol, D. M

    Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016     420 - 426  2017.01

     View Summary

    © 2017 Taylor & Francis Group, London.This paper presents a probabilistic framework for the life-cycle reliability assessment of existing bridges under multiple hazards. The life-cycle reliability of a bridge girder under traffic and airborne chloride hazards is compared with that of a bridge pier under seismic and airborne chloride hazards. When predicting the life-cycle reliability of existing bridges, observational data from inspection could be used to estimate the current material corrosion level. Random variables associated with the prediction of time-variant steel weight loss are updated by using Sequential Monte Carlo Simulation (SMCS). The life-cycle reliability of two bridge components under various hazards and inspection results are discussed in an illustrative example.

  • Assessment of the structural behavior of corrosion-affected rc beams: Experimental study and modeling

    Lim, S, Akiyama, M, Frangopol, D. M

    Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016     379 - 384  2017.01

     View Summary

    © 2017 Taylor & Francis Group, London.Structural performance of deteriorated reinforced concrete (RC) members depends on the magnitude and location of steel corrosion. Finite element (FE) method has been applied to the structural performance assessment of corroded RC members; however, the difficulty in quantifying cross-sectional area of rebar embedded into the concrete has been reported as a main challenge for conducting the FE analysis precisely. The two main objectives of this paper are to: (1) experimentally investigate the effects of spatial variability associated with steel corrosion on the structural behavior of a corroded RC beam and (2) establish a FE numerical modeling to assess the structural performance of corroded RC beams. In the experimental study, the spatial variability associated with the steel weight loss over the RC beam is quantified using X-ray and digital image processing techniques. This experimental result is used as input data for the FE analysis. The proposed model provides good agreement with the test results.

  • Ground motion estimation for the elevated bridges of the Kyushu Shinkansen derailment caused by the foreshock of the 2016 Kumamoto earthquake based on the site-effect substitution method 2016 Kumamoto earthquake sequence and its impact on earthquake science and hazard assessment Manabu Hashimoto, Martha Savage, Takuya Nishimura and Haruo Horikawa

    Yoshiya Hata, Masaaki Yabe, Akira Kasai, Hiroshi Matsuzaki, Yoshikazu Takahashi, Mitsuyoshi Akiyama

    Earth, Planets and Space   68 ( 1 )  2016.12  [Refereed]

     View Summary

    An earthquake of JMA magnitude 6.5 (first event) hit Kumamoto Prefecture, Japan, at 21:26 JST, April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (second event) hit Kumamoto and Oita Prefectures at 01:46 JST, April 16, 2016. An out-of-service Kyushu Shinkansen train carrying no passengers traveling on elevated bridges was derailed by the first event. This was the third derailment caused by an earthquake in the history of the Japanese Shinkansen, after one caused by the 2004 Mid-Niigata Prefecture Earthquake and another triggered by the 2011 Tohoku Earthquake. To analyze the mechanism of this third derailment, it is crucial to evaluate the strong ground motion at the derailment site with high accuracy. For this study, temporary earthquake observations were first carried out at a location near the bridge site; these observations were conducted because although the JMA Kumamoto Station site and the derailment site are closely located, the ground response characteristics at these sites differ. Next, empirical site amplification and phase effects were evaluated based on the obtained observation records. Finally, seismic waveforms during the first event at the bridge site of interest were estimated based on the site-effect substitution method. The resulting estimated acceleration and velocity waveforms for the derailment site include much larger amplitudes than the waveforms recorded at the JMA Kumamoto and MLIT Kumamoto station sites. The reliability of these estimates is confirmed by the finding that the same methods reproduce strong ground motions at the MLIT Kumamoto Station site accurately. These estimated ground motions will be useful for reasonable safety assessment of anti-derailment devices on elevated railway bridges.[Figure not available: see fulltext.]

    DOI

  • Ground motion estimation for the elevated bridges of the Kyushu Shinkansen derailment caused by the foreshock of the 2016 Kumamoto earthquake based on the site-effect substitution method 2016 Kumamoto earthquake sequence and its impact on earthquake scien

    Hata, Yoshiya, Yabe, Masaaki, Kasai, Akira, Matsuzaki, Hiroshi, Takahashi, Yoshikazu, Akiyama, Mitsuyoshi

    Earth, Planets and Space   68 ( 1 )  2016.12  [Refereed]

     View Summary

    © 2016 The Author(s).An earthquake of JMA magnitude 6.5 (first event) hit Kumamoto Prefecture, Japan, at 21:26 JST, April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (second event) hit Kumamoto and Oita Prefectures at 01:46 JST, April 16, 2016. An out-of-service Kyushu Shinkansen train carrying no passengers traveling on elevated bridges was derailed by the first event. This was the third derailment caused by an earthquake in the history of the Japanese Shinkansen, after one caused by the 2004 Mid-Niigata Prefecture Earthquake and another triggered by the 2011 Tohoku Earthquake. To analyze the mechanism of this third derailment, it is crucial to evaluate the strong ground motion at the derailment site with high accuracy. For this study, temporary earthquake observations were first carried out at a location near the bridge site; these observations were conducted because although the JMA Kumamoto Station site and the derailment site are closely located, the ground response characteristics at these sites differ. Next, empirical site amplification and phase effects were evaluated based on the obtained observation records. Finally, seismic waveforms during the first even

    DOI

  • Assessment of the structural performance of corrosion-affected RC members based on experimental study and probabilistic modeling

    Sopokhem Lim, Mitsuyoshi Akiyama, Dan M. Frangopol

    Engineering Structures   127   189 - 205  2016.11  [Refereed]

     View Summary

    The severity of damage due to corrosion on reinforced concrete (RC) structures primarily depends on the magnitude and location of the steel corrosion. A finite element (FE) method has been used to evaluate the structural performance of RC members subjected to reinforcement corrosion. However, the difficulty in quantifying the residual rebar cross-sections in the concrete has been reported as the primary challenge in providing important parameters for modeling the corrosion damages on the steel reinforcement and concrete. The three primary objectives of this paper are to (a) experimentally investigate the effects of the spatial variability in the steel corrosion on the structural behaviors of five corroded RC beams, (b) establish a FE method to assess their deteriorated structural performances, and (c) develop Gumbel distribution parameters to estimate the spatial variability of corrosion for the rebars. In the experimental study, the spatial variability in the steel weight loss along the corroded rebars in the concrete medium was quantified using X-ray and digital image processing techniques. For the FE analysis, the experimental steel weight loss data was used for modeling the residual steel cross-sections, reduced concrete strength, and deteriorated bond interface. The flexural capacity obtained from the simulated beams is in agreement with experimental results.

    DOI

  • Performance indicators for structural systems and infrastructure networks

    M. Ghosn, L. Dueñas-Osorio, D. M. Frangopol, T. P. McAllister, P. Bocchini, L. Manuel, B. R. Ellingwood, S. Arangio, F. Bontempi, M. Shah, M. Akiyama, F. Biondini, S. Hernandez, G. Tsiatas

    Journal of Structural Engineering (United States)   142 ( 9 )  2016.09  [Refereed]

     View Summary

    Establishing consistent criteria for assessing the performance of structural systems and infrastructure networks is a critical component of communities' efforts to optimize investment decisions for the upkeep and renewal of the built environment. Although member-level performance and reliability assessment procedures are currently well-established, it is widely recognized that a member-oriented approach does not necessarily lead to an efficient utilization of limited resources when making decisions related to the management of existing deteriorating structures or lifeline systems, especially those that may be exposed to extreme events. For this reason, researchers have renewed their interests in developing system-level assessment methods as a basis to modern structural and infrastructure performance evaluation and design processes. Specifically, system-level performance metrics and characteristics such as reliability, redundancy, robustness, resilience, and risk continue to be refined. The objective of this paper is to extend the content of the accompanying paper on reliability-based performance indicators for structural members by reviewing proposals for the development and implementation of performance-based criteria for structural systems and infrastructure networks. The paper reviews established concepts of reliability design along with emerging ideas of performance-based and resilience-based design that are especially relevant for assessing and managing system-level risk. The paper also studies structural redundancy and robustness concepts as well as network-level performance metrics along with ranking approaches. Insights from these analyses reveal the need for transitioning structural and infrastructure design processes from a traditional component-level reliability-based approach, to one that seeks uniform levels of risk across scales (from structural systems to interconnected infrastructure networks across communities). Implementation examples are drawn from experiences with buildings, bridges, offshore oil and gas platforms, and a variety of infrastructure systems. The paper also reflects on promising avenues for pursuing practical and calibrated system-level performance indicators that support life cycle performance, safety, reliability, and risk of structural and infrastructure systems as integral parts of resilient communities.

    DOI

  • Updating the Seismic Reliability of Existing RC Structures in a Marine Environment by Incorporating the Spatial Steel Corrosion Distribution: Application to Bridge Piers

    Yanweerasak Thanapol, Mitsuyoshi Akiyama, Dan M. Frangopol

    Journal of Bridge Engineering   21 ( 7 )  2016.07  [Refereed]

     View Summary

    Although several models are available for evaluating the structural performance of corroded reinforced concrete (RC) structures, seismic reliability assessments considering the effect of steel corrosion are currently scarce. Determining how long existing RC structures in an aggressive environment will be able to have a seismic safety level greater than the threshold remains difficult. Life-cycle reliability assessments of these structures under seismic hazards and hazards associated with airborne chloride are discussed in this paper. When predicting the seismic reliability of existing RC structures, observational data from inspection and/or nondestructive testing methods could be used to estimate the current material corrosion level. Considering the effect of steel corrosion in the plastic hinges of deteriorating structures on their seismic capacity is important. The displacement ductility capacity at the occurrence of longitudinal buckling of rebar in RC structures depends on the steel corrosion level in the plastic hinges. In this paper, the methodology to estimate the mean and variance of steel weight loss in the plastic hinge of corroded RC structures based on inspection results is presented. The number and space interval of inspection locations are considered when conducting the statistical estimation error process. The parameters to estimate the steel weight loss in the plastic hinges incorporating the spatial variability in steel corrosion are derived from experimental results to visualize the steel corrosion in RC members by X-ray technology. In addition, random variables associated with the prediction of time-variant steel weight loss are updated by sequential Monte Carlo simulations (SMCS) for consistency with the inspection results. The epistemic uncertainties can be reduced by SMCS. This process helps to conduct the reliability analysis more precisely. In this paper, a novel procedure for estimating the reliability-based life-cycle seismic reliability of existing RC structures in a marine environment by incorporating the spatial steel corrosion distribution is presented. In an illustrative example, the effects of the inspection results and frequency and the hazards associated with airborne chloride on the updated cumulative-time failure probability of a RC bridge pier in an earthquake-prone region are discussed.

    DOI

  • Reliability-based assessment of structures for extreme events

    Mitsuyoshi Akiyama

    IABSE Summit 2016    2016.03  [Invited]

  • Lessons from the 2016 Kumamoto earthquake based on field investigations of damage to bridges

    Mitsuyoshi Akiyama, Yoshikazu Takahashi, Yoshiya Hata, Riki Honda

    International Journal of Earthquake and Impact Engineering   1 ( 3 ) 225 - 225  2016

    DOI

  • Partial factors for reliability-based durability assessment of RC bridges using observational data

    K. Kano, Y. Odake, M. Akiyama, D. M. Frangopol

    Maintenance, Monitoring, Safety, Risk and Resilience of Bridges and Bridge Networks - Proceedings of the 8th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2016     147 - 151  2016  [Refereed]

     View Summary

    Reinforced concrete (RC) bridges in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. This paper presents a methodology for reliability-based durability assessment of RC bridges in a marine environment. A simple assessment criterion using partial factors that satisfy the target reliability level within the remaining lifetime of existing RC bridges is presented. A procedure to obtain the partial factors updated by the Sequential Monte Carlo Simulation is presented. In this procedure, the chloride concentration distribution by coring test is used as observational data. Partial factors are determined by taking into consideration the reduction in the uncertainty associated with the prediction of chloride-induced corrosion. Therefore, taking into account the reduction in the epistemic uncertainty, the values of the partial factors for durability assessment are different from those used for durability design.

  • Investigation of the spatial variability of steel weight loss and corrosion cracking: A novel x-ray technique

    Sopokhem Lim, Haitao Jiang, Mitsuyoshi Akiyama

    International Conference on Durability of Concrete Structures, ICDCS 2016     265 - 269  2016  [Refereed]

     View Summary

    The performance of corrosion-affected RC members depends strongly on localized damages of reinforcement. Therefore, modeling the spatial variability of steel corrosion is very important for the assessment of the remaining service life of corroded structures or time for maintenance. To study the changes of spatial variability of steel weight loss over time, a continuous monitoring is necessary. In this paper, a novel procedure of X-ray technique application in monitoring the spatial growth of a corroded bar in a RC specimen is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. The relationship of steel weight loss and corrosion cracking is studied at different stages of corrosion. The validity of the estimation method of steel weight loss is also presented.

    DOI

  • ANALYSIS OF "ANTI-CATASTROPHE" PROPERTY IN JRA AND FOREIGN DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES

    TAKAHASHI Yoshikazu, AKIYAMA Mitsuyoshi, KATAOKA Shojiro, HONDA Riki

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   72 ( 4 ) I_821 - I_830  2016

     View Summary

    As the lessons from severe damage of civil infrastructures due to Tsunami and ground motion in the 2011 Great East Japan Earthquake, "Anti-Catastrophe" concept can be a paradigm shift in structural / seismic design method. In a conventional design, seismic safety of a structural system is verified against "design" ground motion. But "Anti-Catastrophe" concept requests for structural designers to concern the possibility of catastrophic event caused by severe action unestimated in the design method. JRA Design Specifications for Highway Bridges was revised in 2012 and a principle similar to "Anti-Catastrophe" concept was adopted. In this paper, "Anti-Catastrophe" concept in the specifications is summirised and challenges are considered to produce effective measure in seismic design method based on the review of recent domestic and foreign trend of structural design.

    DOI CiNii

  • DAMAGE ANALYSIS OF RC RIGID FRAME VIADUCTS AFFECTED BY 2011 GREAT EAST JAPAN EARTHQUAKE

    UNO Kunihiko, INABA Tomoya, KOBAYASHI Masashi, AKIYAMA Mitsuyoshi

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   72 ( 4 ) I_506 - I_514  2016

     View Summary

    This paper describes the damage to RC rigid frame viaducts caused by the 2011 Great East Japan earthquake. In this study, a three-dimensional dynamic nonlinear analysis is carried out to investigate the extent of seismic damage of Daiichi Nakasone Viaduct columns with the scenario earthquake. The mechanism of the damage to each column members (side part of columns and middle part of ones) and the dynamic behaviour of the structure are also studied. Inparticular, the reason of the different degrees of damage in side and middle columns is considered in detail. The analytical results show that the greater rotational mode of deformation caused by the acceleration and displacement response in the perpendicular direction in the side columns is the main reason of the greater degree of damage in them as compared with the middle columns.

    CiNii

  • SEISMIC DESIGN METHOD TO CONSIDER "ANTI-CATASTROPHE" CONCEPT — A STUDY FOR THE DRAFT OF DESIGN —

    HONDA Riki, AKIYAMA Mitsuyoshi, KATAOKA Shojiro, TAKAHASHI Yoshikazu, NOZU Atsushi, MURONO Yoshitaka

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   72 ( 4 ) I_459 - I_472  2016

     View Summary

    It is requested to implement the concept of "anti-catastrophie" property in the seismic design codes. It is not, however, a straight forward task because "anti-catastrophe" concept has various significant differences from existing design codes. This paper identifies problems of the development of "anti-catastrophe"- oriented seismic design codes, and proposed a new concept of "category 2." A framework of design code with "category 2" is also presented. We also discussed conditions required for the society and government to make such new design codes effective, based on theoretical framework of risk governance and proposed several practical policies.

    DOI CiNii

  • 塩害環境下にあるPC桁に生じる鋼材腐食の空間変動性の確率・統計的表現とそのライフサイクル信頼性解析に関する基礎的研究

    福島広之, 櫻井絢子, 宮本祥平, 秋山充良

    コンクリート工学年次論文集   38 ( 2 ) 1561 - 1566  2016  [Refereed]

  • 南海トラフ地震の影響を受けるRCラーメン高架橋の強震動および津波による損傷確率の比較

    名波健吾, 磯辺弘司, 秋山充良, 越村俊一

    コンクリート工学年次論文集   38 ( 2 ) 877 - 882  2016  [Refereed]

  • Flexural behavior prediction of SFRC beams: A novel X-ray technique

    Lim, S, Okamoto, T, Matsuda, M, Akiyama, M

      38 ( 2 ) 1351 - 1356  2016  [Refereed]

  • Investigation of the spatial variability of steel weight loss and corrosion cracking: A novel x-ray technique

    Lim, Sopokhem, Jiang, Haitao, Akiyama, Mitsuyoshi

    International Conference on Durability of Concrete Structures, ICDCS 2016     265 - 269  2016.01

     View Summary

    The performance of corrosion-affected RC members depends strongly on localized damages of reinforcement. Therefore, modeling the spatial variability of steel corrosion is very important for the assessment of the remaining service life of corroded structures or time for maintenance. To study the changes of spatial variability of steel weight loss over time, a continuous monitoring is necessary. In this paper, a novel procedure of X-ray technique application in monitoring the spatial growth of a corroded bar in a RC specimen is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. The relationship of steel weight loss and corrosion cracking is studied at different stages of corrosion. The validity of the estimation method of steel weight loss is also presented.

  • 本震観測記録を利用した2003 年三陸南地震における猪鼻高架橋および中曽根高架橋での地震動の推定

    秦吉弥, 秋山充良, 高橋良和, 野津厚

    構造工学論文集   61A   174 - 187  2015.03

  • 点検・検査情報を活用した既存RC構造物の耐久信頼性照査に用いる部分係数

    狩野淳一, 秋山充良, 吉田郁政

    構造工学論文集   61A   81 - 90  2015.03

  • Preface

    Hitoshi Furuta, Dan M. Frangopol, Mitsuyoshi Akiyama

    Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014     XXIII  2015

  • 「危機耐性」を考慮した耐震設計体系(3)道路橋示方書から読み取る「危機耐性」と国内外の動向を踏まえた課題の整理

    高橋良和, 秋山充良, 片岡正次郎, 本田利器

    第35回地震工学研究発表会講演論文集     No.806 - No.806  2015

  • Life-cycle design of bridges in seismic regions based on lessons from the 2011 great east Japan earthquake

    Mitsuyoshi Akiyama, Dan M. Frangopol

    UNCECOMP 2015 - 1st ECCOMAS Thematic Conference on Uncertainty Quantification in Computational Sciences and Engineering     378 - 393  2015  [Refereed]

     View Summary

    Many bridges in Tohoku region of Japan were damaged and collapsed due to strong ground motions and/or liquefaction during the 2011 Great East Japan earthquake. Bridge superstructures were washed away due to the subsequent tsunami. In addition, bridges in the coastal area deteriorated further due to chloride induced corrosion. It is important to note that the seismic events can cause multiple disasters. The bridges located near the coastline in Japan need to be designed taking into consideration the risk associated with seismic and tsunami hazards, and continuous deterioration. This paper provides a key aspect of lifecycle design of bridges under multiple hazards, with an emphasis on earthquake, tsunami and continuous deterioration based on lessons learned from the 2011 Great Japan earthquake. A simple durability design criterion of reinforced concrete (RC) bridge in a marine environment is proposed to determine the concrete quality and concrete cover to prevent the chlorideinduced reinforcement corrosion causing the deterioration of structural performance during the whole lifetime. In addition, reliability-based capacity design of bridges with a hierarchy of resistance of the various structural components necessary to avoid catastrophic damage and to ensure prompt restoration after an extreme event is discussed.

    DOI

  • Experimental investigation on the relationship between the spatial variation of steel weight loss and the cracking width of RC members using X-ray photograms

    S. Lim, H. Jiang, M. Akiyama, D. M. Frangopol

    Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014     429 - 436  2015  [Refereed]

     View Summary

    Deterioration of RC members due to chloride-induced corrosion of reinforcing bars is a common problem in marine environment. After surface crack initiates, RC structures are prone to the occurrence of longitudinal surface cracks and concrete spalling. These deterioration mechanisms adversely cause significant reduction of the service life and performance of RC members. Therefore, it is important to create models to reliably predict the long-term performance of deteriorated RC structures. However, the very limited amount of experimental data on spatial variation of steel weight loss in relation to propagation of surface cracking widths has been reported to create difficulty in improving the degree of accuracy associated with the prediction models. This paper is aimed to experimentally investigate the non-uniform distribution of steel weight loss along reinforcing bars inside RC means by means of X-ray radiography and its correlation with longitudinal crack widths.

    DOI

  • サイト特性を考慮した強震動によるRCラーメン高架橋の地震被害分析に関する基礎的研究, コンクリート工学年次論文集

    石橋寛樹, 秦吉弥, 秋山充良

    コンクリート工学年次論文集   37 ( 2 ) 955 - 960  2015

  • Visualization of corroded steel bars in RC beams usiging digita image processing of X-ray photograms

    Lim, S, Jiang, H, Okamoto, T, Akiyama, M

    コンクリート工学年次論文集   37 ( 2 ) 1327 - 1332  2015

  • [Invited Lecture]Long term performance of concrete bridges under extreme events

    Mitsuyoshi Akiyama, Dan M. Frangopol

    Proceedings of 9th Austroads Bridge Conference    2014.10

  • Long-term seismic performance of RC structures in an aggressive environment: Emphasis on bridge piers

    Mitsuyoshi Akiyama, Dan M. Frangopol

    Structure and Infrastructure Engineering   10 ( 7 ) 865 - 879  2014.07  [Refereed]

     View Summary

    Even though accurate structural models have been developed for the performance of corroded structures subjected to monotonic flexure and/or shear, studies on seismic performance that include corrosion damage are scarce. For the lifetime assessment of structures in aggressive environments and earthquake-prone regions, the effects of corrosion on seismic performance need to be taken into consideration. Whereas the seismic demand depends on the results of seismic hazard assessment, the deterioration of seismic capacity depends on the environmental hazard assessment. The analysis of the life-cycle reliability of corroded reinforced concrete (RC) structures under earthquake excitations is the topic of this paper. It includes (a) estimation of the seismic capacity of corroded RC components; (b) seismic and airborne chloride hazard assessment and (c) life-cycle seismic reliability of bridges with corrosion damage. In particular, this paper introduces the visualisation of corrosion process in RC members using X-ray for modelling the spatial variability of rebar corrosion. A novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life-cycle seismic reliability of bridge piers is presented. © 2013 © 2013 Taylor & Francis.

    DOI

  • 更新理論とマルコフ連鎖モデルを用いた鉄筋コンクリート構造物の塩害劣化予測に関する基礎的研究

    竹中孔信, 萩野統也, 秋山充良, 吉田郁政

    コンクリート工学年次論文集   36 ( 2 ) 1357 - 1362  2014.07

  • [Keynote Lecture] Bridge life-cycle performance and lessons from infrastructure failures due to the 2011 Great East Japan earthquake and tsunami

    Dan M. Frangopol, Mitsuyoshi Akiyama

    Proceedings of 1st International Conference on Infrastructure Failures and Consequences     1 - 13  2014.07

  • SPGA モデルと経験的サイト増幅・位相特性を考慮した2011 年東北地方太平洋沖地震における長町高架橋での地震動とフラジリティカーブの評価

    秦吉弥, 秋山充良, 高橋良和, 後藤浩之, 野津厚, 一井康二

    構造工学論文集   60A   214 - 227  2014.03

  • Reliability of Bridges under Seismic and Tsunami Hazards

    Mitsuyoshi Akiyama, Dan M. Frangopol

    Vulnerability, Uncertainty, and Risk: Quantification, Mitigation, and Management - Proceedings of the 2nd International Conference on Vulnerability and Risk Analysis and Management, ICVRAM 2014 and the 6th International Symposium on Uncertainty Modeling and Analysis, ISUMA 2014     1696 - 1705  2014  [Refereed]

     View Summary

    In the Tohoku region, the effects of the seismic shocks and the tsunami waves due to the 2011 Great East Japan earthquake were felt with very high intensity. Many structures and infrastructures were severely damaged or washed away. Because tsunami effects have not been taken into consideration in the seismic design and retrofit specifications in Japan, code provisions regarding tsunamis need to be established based on the failure mechanisms observed in the tsunami-induced damage to bridges. In this paper, using both analytical fragility curves and tsunami hazard curves, the basic procedure to estimate the failure probability associated with tsunami hazard is presented. The tsunami fragility of a concrete girder bridge is estimated based on Monte Carlo Simulation (MCS). Seismic reliability of a bridge is compared with tsunami reliability of the same bridge. The need to consider the tsunami effect in the design of concrete girder bridge is discussed in an illustrative example.

    DOI

  • Reliability assessment of RC structures subjected to carbonation by incorporating spatial variations

    T. Hagino, M. Akiyama, Dan M. Frangopol

    Sustainable Development of Critical Infrastructure - Proceedings of the 2014 International Conference on Sustainable Development of Critical Infrastructure     115 - 122  2014  [Refereed]

     View Summary

    When carbonation reaches the depth of the rebar embedded into the concrete, the high alkalinity of the concrete pore solution is neutralised and hydration products are dissolved. As carbonation progresses, the corrosion could extend enough to deteriorate the structural performance. In this paper, a time-dependent structural reliability analysis method, taking the carbonation into consideration, is proposed. To predict the corrosion process of reinforced concrete (RC) structures, spatial variability of corrosion has to be considered. A computational procedure to integrate the spatial variability of corrosion due to carbonation into life-cycle reliability assessment of existing RC structures is established. An illustrative example of a RC structure subjected to carbonation is presented. The emphasis is placed on investigating the effects of the spatial variation of inspected carbonation depths on the reliability estimates of RC structures. © 2014 American Society of Civil Engineers.

    DOI

  • Life-cycle reliability of RC jetties in a marine environment using markov model and sequential monte carlo simulation

    K. Takenaka, M. Akiyama, D. M. Frangopol, I. Yoshida

    Bridge Maintenance, Safety, Management and Life Extension - Proceedings of the 7th International Conference of Bridge Maintenance, Safety and Management, IABMAS 2014     231 - 236  2014  [Refereed]

     View Summary

    Reinforced concrete (RC) structures in a marine environment deteriorate with time due to chloride- induced corrosion of reinforcing bars. In this paper, a methodology for quantifying life-cycle reliability of RC jetties subjected to chloride attack is presented. The deterioration process of a RC jetty regarding the transition between the condition states is modeled as a Markov process. In addition, a procedure to obtain the transition probability matrix at time t after construction updated by the Sequential Monte Carlo Simulation (SMCS) method is indicated. Transition probability matrix could be updated in order to be consistent with the observational information. The methodology is illustrated on the superstructures of RC jetties located in a splash zone. The effect of the updating on the life-cycle reliability estimate of RC jetties is also discussed. © 2014 Taylor & Francis Group.

    DOI

  • Performance analysis of Tohoku-Shinkansen viaducts affected by the 2011 Great East Japan earthquake

    Mitsuyoshi Akiyama, Dan M. Frangopol, Keita Mizuno

    STRUCTURE AND INFRASTRUCTURE ENGINEERING   10 ( 9 ) 1228 - 1247  2014  [Refereed]

     View Summary

    Tohoku-Shinkansen viaducts in eastern Japan were designed in accordance with specifications published in the 1970s. They have less shear reinforcement than required by current design specifications. Consequently, the No. 5 Inohana viaducts of Tohoku-Shinkansen failed in shear during the 2003 Sanriku-Minami earthquake. The viaducts were retrofitted by means of steel jacketing so that they had sufficient shear capacity. The retrofitted columns of the viaducts performed well during the 2011 Great East Japan earthquake. However, there is a lack of understanding of the impact of these retrofitting interventions on the vulnerability of the viaduct. It is important to recognise the relationship between the damage to the Shinkansen viaduct with retrofitted reinforced concrete columns and the ground motion intensity. After a brief review of the history of the performance of Shinkansen viaducts to several earthquakes prior to the 2011 Great East Japan earthquake, this paper presents fragility curves of the retrofitted and non-retrofitted Tohoku-Shinkansen viaducts based on nonlinear dynamic analyses and Monte Carlo simulation. It was found that the median of the fragility curve associated with the ultimate limit state for retrofitted viaduct is at least five times larger than that for as-built viaduct.

    DOI

  • Integrated Evaluation of Structural Performance over Time of Concrete Structures with Chloride Induced Damage

    Concrete Journal (Tokyo. 1963)   52 ( 3 ) 243 - 250  2014

     View Summary

    This paper presents some of the results achieved by Technical Committee on Systematization to Evaluate Structure and Durability Performance in Corroded RC Structure, which works to establish the use of numerical structural analysis as an evaluation method that allows numerical representation in space and time of durability of concrete structures with chloride induced damage(hereinafter, structural performance over time), and an index of structural performance over time allowing the evaluation of total structural systems. This paper covers in particular methods to evaluate the spatial variability of the amount of corrosion that affects structural performance using probabilistic and statistical techniques, and constitutive models related to reinforcement corrosion and the bond between concrete and corroded reinforcement, which are essential for the finite element analysis of corroded concrete structures. Further, an index of structural performance over time is proposed and formulated, and trial calculation results for total structural systems are introduced.

    CiNii

  • STRONG MOTION ESTIMATION ALONG ODAKI AND HIEDA VIADUCTS FOR THE 2003 SOUTHERN SANRIKU EARTHQUAKE BASED ON ASPERITY MODEL CONSIDERING EMPIRICAL SITE AMPLIFICATION AND PHASE EFFECTS

    HATA Yoshiya, TAKAHASHI Yoshikazu, AKIYAMA Mitsuyoshi, GOTO Hiroyuki, NOZU Atsushi

    PROCEEDINGS OF THE JSCE EARTHQUAKE ENGINEERING SYMPOSIUM   70 ( 4 ) I_560 - I_577  2014

     View Summary

    Serious damage occurred at RC rigid frame viaduct sites of Tohoku Shinkansen in Esashi Ward, Oshu City, during the 2003 Southern Sanriku Earthquake (MJ7.1). In order to analyze the damage mechanism, it is important to evaluate strong ground motions at the viaduct sites with high accuracy, taking into account site effects. In this study, temporary seismic observation with very high density was conducted along the viaduct sites. Moreover, seismic waveforms along the viaduct were estimated based on the asperity model considering empirical site amplification and phase effects. The estimated ground motions will be useful in the detailed study of the damage mechanism.

    CiNii

  • Long-term seismic performance of RC structures in an aggressive environment: emphasis on bridge piers

    Mitsuyoshi Akiyama, Dan M. Frangopol

    STRUCTURE AND INFRASTRUCTURE ENGINEERING   10 ( 7 ) 865 - 879  2014

     View Summary

    Even though accurate structural models have been developed for the performance of corroded structures subjected to monotonic flexure and/or shear, studies on seismic performance that include corrosion damage are scarce. For the lifetime assessment of structures in aggressive environments and earthquake-prone regions, the effects of corrosion on seismic performance need to be taken into consideration. Whereas the seismic demand depends on the results of seismic hazard assessment, the deterioration of seismic capacity depends on the environmental hazard assessment. The analysis of the life-cycle reliability of corroded reinforced concrete (RC) structures under earthquake excitations is the topic of this paper. It includes (a) estimation of the seismic capacity of corroded RC components; (b) seismic and airborne chloride hazard assessment and (c) life-cycle seismic reliability of bridges with corrosion damage. In particular, this paper introduces the visualisation of corrosion process in RC members using X-ray for modelling the spatial variability of rebar corrosion. A novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life-cycle seismic reliability of bridge piers is presented.

    DOI

  • Performance analysis of Tohoku-Shinkansen viaducts affected by the 2011 Great East Japan earthquake

    Mitsuyoshi Akiyama, Dan M. Frangopol, Keita Mizuno

    Structure and Infrastructure Engineering   10 ( 9 ) 1228 - 1247  2014

     View Summary

    Tohoku-Shinkansen viaducts in eastern Japan were designed in accordance with specifications published in the 1970s. They have less shear reinforcement than required by current design specifications. Consequently, the No. 5 Inohana viaducts of Tohoku-Shinkansen failed in shear during the 2003 Sanriku-Minami earthquake. The viaducts were retrofitted by means of steel jacketing so that they had sufficient shear capacity. The retrofitted columns of the viaducts performed well during the 2011 Great East Japan earthquake. However, there is a lack of understanding of the impact of these retrofitting interventions on the vulnerability of the viaduct. It is important to recognise the relationship between the damage to the Shinkansen viaduct with retrofitted reinforced concrete columns and the ground motion intensity. After a brief review of the history of the performance of Shinkansen viaducts to several earthquakes prior to the 2011 Great East Japan earthquake, this paper presents fragility curves of the retrofitted and non-retrofitted Tohoku-Shinkansen viaducts based on nonlinear dynamic analyses and Monte Carlo simulation. It was found that the median of the fragility curve associated with the ultimate limit state for retrofitted viaduct is at least five times larger than that for as-built viaduct. © 2013 © 2013 Taylor & Francis.

    DOI

  • 摩擦振子免震機構を有するコンクリート橋脚に生じる地震後の残留変位に関する実験的検討

    金井晴弘, 阿部遼太, 秋山充良, 小野潔

    コンクリート工学年次論文集   35 ( 2 ) 811 - 816  2013.06

  • [Early Career Keynote Lecture] Life-cycle design of bridges under multiple hazards: Earthquake, tsunami and continuous deterioration

    Akiyama, M, Frangopol, D.M

    11th ICOSSAR (International Conference of Structural Safety and Reliability)    2013.06

  • Reliability of bridges under tsunami hazards: Emphasis on the 2011 Tohoku-Oki Earthquake

    Akiyama, M, Frangopol, D.M, Arai, M, Koshimura, S

    Earthquake Spectra   29 ( S1 ) S295 - S314  2013.05

  • Reliability of bridges under tsunami hazards: Emphasis on the 2011 Tohoku-oki earthquake

    Mitsuyoshi Akiyama, Dan M. Frangopol, Megumi Arai, Shunichi Koshimura

    Earthquake Spectra   29 ( SUPPL.1 ) S295 - S314  2013.03  [Refereed]

     View Summary

    The probabilistic estimation of tsunami impact on bridges and the evaluation of potential tsunami risk are important topics, but they are still in very early stages of development. First, this paper presents the damage of bridges during the great Tohoku-oki earthquake and giant tsunami of 11 March 2011 based on the field damage investigation. The damage conditions and the possible failure mechanisms of bridges due to tsunami are particularly discussed. Second, tsunami fragility curves are presented. Empirical tsunami fragility curves based on the utilization of damage data associated with past tsunami disasters have been developed. In this paper, the tsunami fragility curves are established based on simulations. Bridge failure probability can be estimated using the tsunami hazard and fragility curves. Finally, an illustrative example of the reliability estimation of a bridge exposed to tsunami hazard is presented. © 2013, Earthquake Engineering Research Institute.

    DOI

  • 高強度RC杭の開発とその構造性能評価に関する実験的研究

    秋山 充良, 内藤 英樹, 三浦 稔, 浅沼 大寿, 荒川 岳, 武田 篤史, 佐藤 啓, 鈴木 基行

    土木学会論文集E2   69 ( 1 ) 118 - 137  2013.03

  • Seismic design of RC bridge piers to ensure the post-disaster functionality of road network

    Y. Nogami, M. Akiyama, D. M. Frangopol

    Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013     3581 - 3586  2013  [Refereed]

     View Summary

    When designing bridges located in seismic hazard zones, the final design has to be determined by taking into consideration the functionality of the post-disaster road network. The effect of inelastic bridge behavior on the deterioration of the functionality of a road network after an earthquake needs to be incorporated in the seismic analysis. This paper deals with risk-based seismic design of RC bridges to ensure a specified postdisaster functionality of the road network. Computational results show that compared with bridges designed to minimize the seismic life-cycle cost, bridges designed taking into consideration the requirement of post-disaster traffic capacity of a road network need to have a higher seismic performance. © 2013 Taylor & Francis Group, London.

  • Updating the reliability of concrete structures subjected to carbonation

    Touya Hagino, Mitsuyoshi Akiyama, Ikumasa Yoshida

    Sustainable Construction Materials and Technologies   2013-August  2013  [Refereed]

     View Summary

    Due to the existence of uncertainties associated with mechanical properties, geometric configuration, loadings, and imperfect knowledge associated with the evaluations and predictions of material deterioration, probabilistic methods have been applied in the design and performance assessment of concrete structures to quantify these unavoidable uncertainties. This paper presents an approach for improving the accuracy in the life-cycle reliability assessment of reinforced concrete (RC) structures subjected to the carbonation by the Sequential Monte Carlo Simulation (SMCS). Using SMCS, multiple random variables related to observation information can be updated simultaneously, even if non-Gaussian random variables are involved and relationships between the observation information and random variables are nonlinear. The effect of the magnitude of inspected carbonation depth on the updated estimates of reliability associated with the occurrence of steel corrosion is discussed in this paper.

  • Risk-based seismic design of RC bridge pier to minimize the post-disaster functionality loss of road networks

    Y. Nogami, S. Arima, M. Akiyama

    Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013    2013  [Refereed]

     View Summary

    When designing bridges located in seismic hazard zones, the final design has to be determined by taking into consideration the functionality of the post-disaster road network. The effect of inelastic bridge behavior on the deterioration of the functionality of a road network after an earthquake needs to be incorporated in the seismic analysis. This paper deals with risk-based seismic design of RC bridges to ensure a specified post-disaster functionality of the road network. Computational results show that compared with bridges designed to minimize the seismic life-cycle cost, bridges designed taking into consideration the requirement of post-disaster traffic capacity of a road network need to have a higher seismic performance.

  • Reliability of as-built and retrofitted single-story RC frames under seismic and tsunami hazards

    S. Takakuma, M. Akiyama, D. M. Frangopol

    Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013     1267 - 1272  2013  [Refereed]

     View Summary

    Many existing bridges designed before the 1995 Hyogo-Ken Nanbu earthquake have been retrofitted to prevent failure from strong excitations. However, in seismic bridge design and retrofit, the tsunami effects have not been taken into consideration. In this paper, using both the analytical fragility curve and tsunami hazard curve, the basic procedure to estimate the failure probability associated with tsunami hazard is presented. The tsunami fragility of a single-story RC rigid frame before and after seismic retrofit is estimated based on Monte Carlo Simulation. Seismic reliability of as-built and retrofitted frames is compared with tsunami reliability of the same frames. The need to consider the tsunami effect in the design of RC frame is discussed in an illustrative example. © 2013 Taylor & Francis Group, London.

  • Reliability estimation of recycled aggregate concrete structure subjected to carbonation

    T. M. Kea, M. Akiyama

    Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013    2013  [Refereed]

     View Summary

    The life-cycle assessment of reinforced concrete structures through economic, environmental, and social impact across the whole service life is now gaining more and more interest in civil engineering. The mechanical properties and long-term performance of structures using recycled aggregate concrete (RAC) were reported to be weaker than those of structures using natural aggregate concrete (NAC) given the same mix proportion. However, the studies on the durability of RAC subjected to carbonation are scare and limited in the literature. The main purpose of this study is to present the computational procedure for the life-cycle reliability estimations of NAC and RAC structures exposed to carbonation. The experimental results of NAC and RAC under the diffusion of carbon dioxide (CO2) are obtained from the literature reviews. A durability design factors and criterion for designing concrete structure using RAC that satisfy the target failure probability is presented. The effects of concrete properties (i.e. water to cement ratio) and concrete cover on the estimation of reliability of structures using natural and recycled aggregate are investigated in an illustrative example.

  • Reliability estimate of RC structures in a marine environment using Markov model and Sequential Monte Carlo Simulation

    K. Takenaka, T. Hagino, M. Akiyama, I. Yoshida

    Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013    2013  [Refereed]

     View Summary

    Reinforced concrete (RC) structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. In this paper, a methodology for quantifying life-cycle reliability of RC structures subjected to chloride attack is presented. The deterioration process of bridge components regarding the transition between the condition states is modeled as a Markov process. In addition, a procedure to obtain the transition probability matrix at time t after construction updated by the Sequential Monte Carlo Simulation (SMCS) is indicated. Transition probability matrix could be updated to be consistent with the observational information. The methodology is illustrated on an existing RC superstructures of wharves located in a splash zone. The effect of the updating on the life-cycle reliability estimate of RC wharves is discussed in this paper.

  • Life-cycle reliability of concrete bridges in an earthquake prone region and aggressive environment

    Shigeru Takakuma, Mitsuyoshi Akiyama

    Sustainable Construction Materials and Technologies   2013-August  2013  [Refereed]

     View Summary

    Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. This paper presents a framework for computing the time-dependent seismic reliability of concrete bridges in an earthquake prone region and a marine environment. It includes: (a) estimate of seismic capacity of corroded RC components; (b) seismic and airborne chloride hazard assessment; and (c) seismic reliability of bridges with corrosion damage. The effects of seismic hazard, hazard associated with airborne chloride, and spatial distribution of steel corrosion on the time-dependent seismic reliability are investigated in this paper. The findings show that the time-dependent reliability of concrete bridge depends on both the seismic and airborne chloride hazards, and that the spatial distribution of steel corrosion has to be taken into consideration in the seismic reliability analysis.

  • Life-cycle design of bridges under multiple hazards: Earthquake, tsunami, and continuous deterioration

    M. Akiyama, D. M. Frangopol

    Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013     3 - 16  2013  [Refereed]

     View Summary

    The 2011 Great East Japan Earthquake caused multiple disasters, including (a) damage and collapse of bridges due to strong ground motions and/or liquefaction and (b) washout of bridge superstructures due to the subsequent tsunami. In addition, bridges in the coastal area deteriorated further due to chlorideinduced corrosion. Procedures for identifying and screening significant threat scenarios and for assessing and mitigating the risk of bridge damage and collapse under multiple hazards can be developed using probabilistic risk assessment.This paper provides a framework for estimating the life-cycle reliability of bridges under multiple hazards, with an emphasis on earthquake, tsunami and continuous deterioration. Reliability-based capacity design of bridges with a hierarchy of resistance of the various structural components necessary to avoid catastrophic damage and to ensure prompt restoration from an extreme event is discussed. © 2013 Taylor & Francis Group, London.

  • Particle filter for model updating and reliability estimation of existing structures

    Ikumasa Yoshida, Mitsuyoshi Akiyama

    Smart Structures and Systems   11 ( 1 ) 103 - 122  2013.01  [Refereed]

     View Summary

    It is essential to update the model with reflecting observation or inspection data for reliability estimation of existing structures. Authors proposed updated reliability analysis by using Particle Filter. We discuss how to apply the proposed method through numerical examples on reinforced concrete structures after verification of the method with hypothetical linear Gaussian problem. Reinforced concrete structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. In the case of existing structures, it is essential to monitor the current condition such as chloride-induced corrosion and to reflect it to rational maintenance with consideration of the uncertainty. In this context, updated reliability estimation of a structure provides useful information for the rational decision. Accuracy estimation is also one of the important issues when Monte Carlo approach such as Particle Filter is adopted. Especially Particle Filter approach has a problem known as degeneracy. Effective sample size is introduced to predict the covariance of variance of limit state exceeding probabilities calculated by Particle Filter. Its validity is shown by the numerical experiments.

    DOI

  • STRONG MOTION ESTIMATION IN SHIZUGAWA, MINAMISANRIKU TOWN, FOR THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE BASED ON A SUPER ASPERITY MODEL CONSIDERING EMPIRICAL SITE AMPLIFICATION AND PHASE EFFECTS

    HATA Yoshiya, AKIYAMA Mitsuyoshi, TAKAHASHI Yoshikazu, GOTO Hiroyuki, NOZU Atsushi, KOSA Kenji

    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN   69 ( 2 ) I_161 - I_166  2013

     View Summary

    Enormous damage occurred to the disaster countermeasures office, the river bridges and the fishery port facilities in Shizugawa, Minamisanriku Town due to the 2011 off the Pacific coast of Tohoku Earthquake (Mw9. 0). To evaluate the performance of structures before the attack of tsunami, it is necessary to estimate strong motions in Shizugawa Area with sufficient accuracy, taking into account site effects. In this study, seismic waveform in Shizugawa Area was estimated based on a super asperity model considering empirical site amplification and phase effects. The estimated seismic waveform will be useful in the detailed study of seismic performance of structures before the attack of tsunami.

    CiNii

  • スーパーアスペリティモデルと経験的サイト増幅・位相特性を考慮した2011年東北地方太平洋沖地震による南三陸志津川での強震動の評価

    秦吉弥, 秋山充良, 高橋良和, 後藤浩之, 野津厚, 幸左賢二

    土木学会論文集B3   69 ( 2 ) I_161 - I_166  2013

  • Particle filter for model updating and reliability estimation of existing structures

    Yoshida, I, Akiyama, M

    Smart Structures & Systems   11 ( 1 ) 103 - 122  2013.01

  • Reliability-based capacity design for reinforced concrete bridge structures

    Mitsuyoshi Akiyama, Hiroshi Matsuzaki, Hai T. Dang, Motoyuki Suzuki

    Structure and Infrastructure Engineering   8 ( 12 ) 1096 - 1107  2012.12  [Refereed]

     View Summary

    In the seismic design of reinforced concrete (RC) bridge structures, there should be no brittle failures, such as shear failures, in the components, and a plastic hinge should be formed at the bottom of the bridge pier. These are important concepts in capacity design to guarantee the safety of bridges subjected to severe earthquakes. These concepts can maximise post-event operability and minimise the cost of repairing bridges after a severe earthquake. In this article, a reliability-based methodology to carry out capacity design with partial factors is proposed and applied to the seismic design of RC bridge structures. This ensures that (i) all of the components undergo the desired ductile failure mode, (ii) the damage due to an earthquake is induced only at the bottom of the bridge pier and (iii) the probability of failure is at most equal to a specified value. © 2012 Copyright Taylor and Francis Group, LLC.

    DOI

  • [Keynote Lecture]Lessons from the 2011 Great East Japan Earthquake: Emphasis on life-cycle structural performance

    Akiyama, M, Frangopol, D.M

    IALCCE (International Symposium on Life-Cycle Civil Engineering)    2012.10

  • Integration of the effects of airborne chlorides into reliability-based durability design of reinforced concrete structures in a marine environment

    Mitsuyoshi Akiyama, Dan M. Frangopol, Motoyuki Suzuki

    Structure and Infrastructure Engineering   8 ( 2 ) 125 - 134  2012  [Refereed]

     View Summary

    In this paper, the hazard curve associated with airborne chlorides in a marine environment and the computational procedure to obtain the probability of occurrence of corrosion cracking in reinforced concrete (RC) structures are presented. A method for integration of the effects of airborne chloride into reliability-based durability design of RC structures in a marine environment is proposed. By using this method, it is possible to determine the probability of corrosion cracking due to airborne chlorides, regardless of region, distance from coastline, and the properties of the concrete controlled by the water to cement ratio. © 2012 Taylor and Francis Group, LLC.

    DOI

  • Probabilistic assessment of structural performance of bridges under tsunami hazard

    M. Akiyama, Dan M. Frangopol, M. Arai, S. Koshimura

    Structures Congress 2012 - Proceedings of the 2012 Structures Congress     1919 - 1928  2012  [Refereed]

     View Summary

    An earthquake can cause multiple disasters. For the reliability estimation of coastal structures and infrastructures in Japan, seismic hazard, tsunami hazard and hazard associated with airborne chlorides need to be taken into consideration. Firstly, this paper presents the damage of bridges during the Great East Japan Earthquake and Tsunami on March 11, 2011 based on the Japan Society of Civil Engineers (JSCE) damage investigation. Especially, the damages condition and the possible failure mechanisms of bridges due to tsunami are discussed based on the field survey. Secondly, the tsunami fragility curves are presented. These are used to estimate the structural fragility under the tsunami hazards. Bridge failure probability can be estimated using the tsunami hazard curve and the fragility curve. Finally, an illustrative example quantifying the effect of bridge pier height on the reliability of a bridge under tsunami hazard is presented. © ASCE 2012.

    DOI

  • Updating the reliability of existing PC bridge girders by incorporating spatial variations

    M. Akiyama, D. M. Frangopol, I. Yoshida

    Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management     602 - 607  2012  [Refereed]

     View Summary

    This paper presents a framework for estimating the time-dependent reliability of prestressed concrete (PC) bridge girders in a marine environment. The analysis considers the spatial variability associated with concrete cover, surface chloride concentration, and coefficient of diffusion of chloride over the entire area. PC bridge girder is modeled as one-dimension spatial model. In addition, random variables for estimating the corrosion process of PC bridge girders are updated based on observational information such as chloride concentration distribution by coring test. Sequential Monte Carlo Simulation (SMCS) is used to update simultaneously multiple random variables relating to observational information. In an illustrative example, the effect of the spatial interval of observational information given by coring test on the updated estimate of a PC bridge girder reliability is investigated. © 2012 Taylor & Francis Group.

    DOI

  • Estimation of steel weight loss due to corrosion in RC members based on digital image processing of X-ray photogram

    M. Akiyama, D. M. Frangopol

    Life-Cycle and Sustainability of Civil Infrastructure Systems - Proceedings of the 3rd International Symposium on Life-Cycle Civil Engineering, IALCCE 2012     1885 - 1891  2012  [Refereed]

     View Summary

    Since structural capacity of RC members depends strongly on localized condition of reinforcements, it is important to model the spatial variability of steel corrosion. However, steel corrosion in RC members can only be observed after severely damaging the concrete member. In order to understand the growth process of steel corrosion and how the spatial variability of steel corrosion increases with time a continuous monitoring is necessary. In this study, X-ray photography is applied to observation of steel corrosion in RC members. The steel weight loss is estimated by using a digital image processing of X-ray photogram. Comparing the steel weight loss estimated by weight measurement with that estimated by the digital image processing, applicability of X-ray photogram for the observation of corrosion process in RC members is demonstrated.

  • Lessons from the 2011 Great East Japan earthquake: Emphasis on life-cycle structural performance

    M. Akiyama, D. M. Frangopol

    Life-Cycle and Sustainability of Civil Infrastructure Systems - Proceedings of the 3rd International Symposium on Life-Cycle Civil Engineering, IALCCE 2012     18 - 35  2012  [Refereed]

     View Summary

    This keynote paper presents the damage of structures and infrastructures in the Tohoku Region during the Great East Japan earthquake and tsunami of March 11, 2011. Field investigations after this earthquake proved the effectiveness of upgrades of seismic specifications and seismic retrofit. Meanwhile, some of existing bridges without seismic retrofit were severely damaged due to strong ground motions. In addition, many superstructures were completely washed away by the tsunami, and several substructures were overturned due to scour. Some of reinforced concrete components and steel bearings were severely deteriorated due to chloride-induced corrosion. Life-cycle reliability of bridges in Japan has to be estimated taking into consideration the seismic hazard, tsunami hazard, and hazard associated with airborne chlorides. Lessons from the 2011 Great East Japan earthquake with emphasis on life-cycle structural performance is the topic of this keynote paper.

  • 変動曲面上を滑る摩擦振子を有するコンクリート橋脚の地震応答特性に関する基礎的研究

    金井晴弘, 阿部遼太, 青木直, 秋山充良

    コンクリート工学年次論文集   34 ( 2 ) 817 - 822  2012

  • 2011 年東北地方太平洋沖地震とフラジリティ解析による鉄道RC1層ラーメン橋脚の耐震補強効果の評価

    水野恵太, 秋山充良

    コンクリート工学年次論文集   34 ( 2 ) 937 - 942  2012

  • Reliability-based capacity design for reinforced concrete bridge structures

    Mitsuyoshi Akiyama, Hiroshi Matsuzaki, Hai T. Dang, Motoyuki Suzuki

    STRUCTURE AND INFRASTRUCTURE ENGINEERING   8 ( 12 ) 1096 - 1107  2012

     View Summary

    In the seismic design of reinforced concrete (RC) bridge structures, there should be no brittle failures, such as shear failures, in the components, and a plastic hinge should be formed at the bottom of the bridge pier. These are important concepts in capacity design to guarantee the safety of bridges subjected to severe earthquakes. These concepts can maximise post-event operability and minimise the cost of repairing bridges after a severe earthquake. In this article, a reliability-based methodology to carry out capacity design with partial factors is proposed and applied to the seismic design of RC bridge structures. This ensures that (i) all of the components undergo the desired ductile failure mode, (ii) the damage due to an earthquake is induced only at the bottom of the bridge pier and (iii) the probability of failure is at most equal to a specified value.

    DOI

  • Integration of the effects of airborne chlorides into reliability-based durability design of R/C structures in a marine environme

    Akiyama, M, Frangopol, D.M, Suzuki, M

    Structure and Infrastructure Engineering   8 ( 2 ) 125 - 134  2012

    DOI

  • Flexural test of precast high-strength reinforced concrete pile prestressed with unbonded bars arranged at the center of the cross-section

    Mitsuyoshi Akiyama, Satoshi Abe, Nao Aoki, Motoyuki Suzuki

    Engineering Structures   34   259 - 270  2012.01  [Refereed]

     View Summary

    In this study, a prestressed reinforced concrete pile that uses high-strength material to increase the pile's flexural capacity was developed. The main structural characteristics of the developed pile include (1) the neutral axis is constantly near the centroidal axis of the pile, even if the longitudinal reinforcement yields due to a flexural moment, because the pile has a high axial compressive force that is induced by prestressed steel bars, and hence, the concrete in the compression region can contribute to increasing the flexural strength of the pile; and (2) the flexural strength of the pile increases because the high-strength concrete is confined by high-strength spirals and carbon-fiber sheets in combination with concrete infilling, and, together, these modifications provide a sufficiently high lateral-confinement pressure. The results of bending tests demonstrate that the proposed prestressed reinforced concrete pile with carbon-fiber sheets and concrete infilling had a much higher flexural capacity than a conventional precast concrete pile. In addition, an analytical approach is presented that can be used to obtain the relationship between the bending moment and the curvature of the proposed pile. Even if concrete bridge systems are constructed on strata that can experience soil liquefaction, such as very soft soil, bridge foundations that use the proposed piles could remain undamaged under the design seismic action. © 2011 Elsevier Ltd.

    DOI

  • Life-cycle reliability of RC bridge piers under seismic and airborne chloride hazards

    Mitsuyoshi Akiyama, Dan M. Frangopol, Hiroshi Matsuzaki

    EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS   40 ( 15 ) 1671 - 1687  2011.12  [Refereed]

     View Summary

    Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. For the life-cycle assessment of RC structures in a marine environment and earthquake-prone regions, the effect of corrosion due to airborne chlorides on the seismic capacity needs to be taken into consideration. Also, the effect of the type of corrosive environment on the seismic capacity of RC structures has to be quantified.

    DOI

  • Life-cycle reliability of RC bridge piers under seismic and airborne chloride hazards

    Mitsuyoshi Akiyama, Dan M. Frangopol, Hiroshi Matsuzaki

    Earthquake Engineering and Structural Dynamics   40 ( 15 ) 1671 - 1687  2011.12

     View Summary

    Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. For the life-cycle assessment of RC structures in a marine environment and earthquake-prone regions, the effect of corrosion due to airborne chlorides on the seismic capacity needs to be taken into consideration. Also, the effect of the type of corrosive environment on the seismic capacity of RC structures has to be quantified. In this paper, the evaluation of the displacement ductility capacity based on the buckling model of longitudinal rebars in corroded RC bridge piers is established, and a novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life-cycle seismic reliability assessment of these piers is proposed. The seismic demand depends on the results of seismic hazard assessment, whereas the deterioration of seismic capacity depends on the hazard associated with airborne chlorides. In an illustrative example, an RC bridge pier was modeled as single degree of freedom (SDOF). The longitudinal rebars buckling of this pier was considered as the sole limit state when estimating its failure probability. The findings show that the life-cycle reliability of RC bridge piers depends on both the seismic and airborne chloride hazards, and that the cumulative-time failure probabilities of RC bridge piers located in seismic zones can be dramatically affected by the effect of airborne chlorides. © 2011 John Wiley & Sons, Ltd.

    DOI

  • Comparison of damage probabilities for the different structures among infrastructures

    中村晋, 安中正, 秋山充良, 篠田昌弘, 鈴木基行

    JCOSSAR2011   Vol.7   391 - 396  2011.10  [Refereed]

     View Summary

    The need to replace conventional methods with performance-based design is well recognized. As performance-based design has come into use around the world, reliability theory will be used for the seismic safety or durability evaluation of concrete structures. The JSCE task committee 336 on “Reliability-Based Design of Concrete Structures” was established in 2006. The objectives of the activities of the committee are to investigate the techniques for introducing reliability-based design into design codes for concrete structures in Japan and, to present the practical examples of seismic safety or durability evaluation for concrete structures based on the reliability theory.

  • Visualization of Corrosion Process in RC Member Using X-Ray

    AKIYAMA Mitsuyoshi, NAKAJIMA Keita, KOMORIYA Takashi

    Concrete Research and Technology   22 ( 3 ) 35 - 45  2011.09

     View Summary

    It is important to estimate the amount of corrosion products in existing RC structures subjected to chloride attack. However, the corrosion process of rebar has not been investigated because of difficulties with observing it. Recently, X-ray technology has been applied to the visualization of concrete cracking to investigate the behavior of fracture process zone in concrete. In this study, digital picture processing method to estimate the amount of corrosion products in RC members is provided for X-ray photography. Then, based on the observation of deteriorated RC member using X-ray photography, corrosion process of rebar is visualized, and the effects of the amount of corrosion products on the corrosion cracking width and flexural strength of RC beam are examined.

    CiNii

  • Long-term seismic performance of RC bridge piers in an aggressive marine environment

    M. Akiyama, Dan M. Frangopol

    Structures Congress 2011 - Proceedings of the 2011 Structures Congress     1907 - 1914  2011  [Refereed]

     View Summary

    For structures located in a moderately or highly aggressive environment, multiple environmental and mechanical stressors lead to deterioration of structural performance and, therefore, create maintenance issues. Such deterioration will reduce the service life of structures. The main purpose of this paper is to discuss a methodology previously proposed by the writers for the evaluation of long-term seismic reliability of reinforced concrete (RC) bridge piers in a marine environment and present new results. This methodology consists of three steps: (1) investigate the relationship between material deterioration and structural performance on an experimental basis; (2) consider both the seismic hazard and the hazard associated with marine environment; and (3) perform an analysis of the long-term seismic performance of RC bridge piers in an aggressive marine environment. © ASCE 2011.

    DOI

  • Ductility evaluation of concrete-encased steel bridge piers subjected to lateral cyclic loading

    Hideki Naito, Mitsuyoshi Akiyama, Motoyuki Suzuki

    Journal of Bridge Engineering   16 ( 1 ) 72 - 81  2011.01  [Refereed]

     View Summary

    An experimental and analytical study was conducted to investigate the ductility of concrete-encased steel piers, referred to as "steel-reinforced concrete (SRC) construction." Based on the cyclic lateral loading tests of SRC column specimens, the restorable and ultimate limit states are defined as the point when concrete cover spalling occurs (equivalent to longitudinal bar buckling) and the point when flange buckling of the H-shaped steel occurs, respectively. To estimate the lateral displacement capacity at both the restorable and ultimate limit states, the curvature distribution of the column was calculated based on the buckling analysis of the longitudinal bar, which was restrained by a concrete cover and transverse reinforcement, and of the steel flange encased in concrete. The lateral displacement was obtained by integrating the curvature distribution. Comparison of the computed results with experimental results, including other writers' reports, confirmed that the proposed method can appropriately estimate the lateral displacement at the restorable and ultimate limit states, and it can accurately evaluate the buckling characteristics of the longitudinal bar and steel flange components of SRC column specimens. © 2011 ASCE.

    DOI

  • Probabilistic approach to service life prediction of concrete structures subjected to load and environmental actions

    Mitsuyoshi Akiyama, Dan M. Frangopol, Ikumasa Yoshida, Hiroaki Tsuruta, Takumi Shimomura

    RILEM Bookseries   5   273 - 281  2011  [Refereed]

     View Summary

    In the design of reinforced concrete (RC) structures in a marine environment, it is important to consider the effects of this environment on structural long-term performance. In this paper, a time-dependent structural reliability analysis method taking the hazard associated with airborne chlorides into consideration is proposed. Also, a procedure to obtain the failure probabilities of RC structures in a marine environment updated by Sequential Monte Carlo Simulation (SMCS) is indicated. In this procedure, the corrosion crack width is used as observational data. For illustrative purposes, time-dependent reliability analyses are presented for one-way RC slabs in a marine environment. Using SMCS, multiple random variables related to observation information can be updated simultaneously. This is realized by taking into consideration the joint probability density functions of the random variables. The effects of the hazard associated with airborne chlorides and an inspection result of corrosion cracking on the updated estimate of one-way RC slab reliability are discussed in this study. © RILEM 2011.

    DOI

  • Lifetime seismic reliability analysis of corroded reinforced concrete bridge piers

    Dan M. Frangopol, Mitsuyoshi Akiyama

    Computational Methods in Applied Sciences   21   527 - 537  2011  [Refereed]

     View Summary

    For structures located in aggressive environments and earthquake regions, it is important to consider the effect of material corrosion on seismic performance. This chapter presents a seismic analysis methodology for corroded reinforced concrete (RC) bridges. It is shown that the analytical results are in good agreement with the experimental results regardless of the amount of steel corrosion. The proposed method is applied to lifetime seismic reliability analysis of corroded RC bridge piers, and the relationship between steel corrosion and seismic reliability is presented. After the occurrence of crack corrosion, seismic reliability of the pier is significantly reduced. If corrosion cracks in the bridge pier are detected by visual inspection, additional detailed inspections need to be performed.

    DOI

  • Reliability analysis of prestressed concrete bridges located in a marine environment

    M. Akiyama, D. M. Frangopol, I. Yoshida

    Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineering     573 - 580  2011  [Refereed]

     View Summary

    There are many kinds of uncertainties involved in the evaluation of corrosion process and deterioration of structural performance. Because of the presence of uncertainties, it is necessary that long-term structural performance be treated based on reliability concepts and methods. This paper presents a probabilistic framework for estimating the time-dependent reliability for existing prestressed concrete structures in a marine environment based on a non-linear filtering technique denoted Sequential Monte Carlo Simulation (SMCS). The results of manual measurement or automatic monitoring are used as observational information. The emphasis is placed on investigating the effects of the differences between manual measurement and automatic monitoring, and possible interruption periods of health monitoring on updated estimates of reliability of prestressed concrete bridges located in a marine environment. © 2011 Taylor & Francis Group, London.

    DOI

  • Reliability estimation of deteriorated RC-structures considering various observation data

    Ikumasa Yoshida, Mitsuyoshi Akiyama

    Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineering     1231 - 1239  2011  [Refereed]

     View Summary

    A reliability estimation method is proposed to estimate the limit state exceeding probability of existing structures considering observation data by Sequential Monte Carlo Simulation (SMCS). Accuracy estimation is one of the important issues when MC approach is adopted. Specifically SMCS approach has a problem known as degeneracy. Effective sample size is introduced to estimate the accuracy of estimated limit state exceeding probabilities. Coefficient of variance of estimated probability is predicted based on the effective sample size ratio of the updated model. The proposed method is demonstrated through a numerical example of reliability analysis on deteriorating RC structures. © 2011 Taylor & Francis Group, London.

    DOI

  • Analytical study on seismic performance of hollow spiral steel pipes under cyclic loading

    Shohei Ohnishi, Kiyoshi Ono, Mitsuyoshi Akiyama

    Procedia Engineering   14   898 - 905  2011  [Refereed]

     View Summary

    The importance of economical construction of infrastructures has recently increased. The application of spiral steel pipes to bridge piers is considered as one of the effective methods. Spiral steel pipes have been seldom used for bridge piers. Currently, spiral steel pipes have been mainly used as the foundations of buildings or bridges and are relatively economical because they are produced in large quantities in factories. However, roll forming processes of spiral steel pipes are different from those of bending roll pipes which have been generally used as bridge piers, so that seismic performance of spiral steel pipes may be different from that of bending roll pipes. Therefore, it is very important to grasp the ultimate strength and the ductility of spiral steel pipes. In this study, the finite element analysis was conducted for grasping the elasto-plastic behavior of hollow spiral steel pipes. Based on the analysis results, the seismic performance of hollow spiral steel pipes under compressive axial force and bending moment was examined and the influences of the structural parameters on the seismic performances of the spiral steel pipes are discussed.

    DOI

  • 高強度構成材料を用いたRC柱の一軸圧縮特性と寸法効果

    阿部諭史, 秋山充良, 鈴木基行

    構造工学論文集   57A   386 - 394  2011

  • 構造形態の工夫によるコンクリート構造の長周期化に関する基礎的研究

    秋山充良, 青木直, 阿部遼太, 黒田千砂子

    コンクリート工学年次論文集   33 ( 2 ) 859 - 864  2011

  • 海洋環境下にあるRC 橋脚のライフタイムにわたる耐震信頼性評価

    松崎裕, 秋山充良, 黒田千砂子

    コンクリート工学年次論文集   33 ( 2 ) 877 - 882  2011

  • X線撮影を用いたRC部材内の鉄筋腐食成長過程の可視化に関する基礎的研究

    秋山充良, 中嶋啓太, 小森谷隆

    コンクリート工学論文集   22 ( 3 ) 35 - 45  2011

  • Ductility Evaluation of Concrete-Encased Steel Bridge Piers Subjected to Lateral Cyclic Loading

    Hideki Naito, Mitsuyoshi Akiyama, Motoyuki Suzuki

    JOURNAL OF BRIDGE ENGINEERING   16 ( 1 ) 72 - 81  2011.01

     View Summary

    An experimental and analytical study was conducted to investigate the ductility of concrete-encased steel piers, referred to as "steel-reinforced concrete (SRC) construction." Based on the cyclic lateral loading tests of SRC column specimens, the restorable and ultimate limit states are defined as the point when concrete cover spalling occurs (equivalent to longitudinal bar buckling) and the point when flange buckling of the H-shaped steel occurs, respectively. To estimate the lateral displacement capacity at both the restorable and ultimate limit states, the curvature distribution of the column was calculated based on the buckling analysis of the longitudinal bar, which was restrained by a concrete cover and transverse reinforcement, and of the steel flange encased in concrete. The lateral displacement was obtained by integrating the curvature distribution. Comparison of the computed results with experimental results, including other writers' reports, confirmed that the proposed method can appropriately estimate the lateral displacement at the restorable and ultimate limit states, and it can accurately evaluate the buckling characteristics of the longitudinal bar and steel flange components of SRC column specimens.

    DOI

  • Book Review -Durability design of concrete structures in severe environments by Odd E. Gjorv (Taylor & Francis, 2009)-

    Mitsuyoshi Akiyama

    Structure and Infrastructure Engineering   7 ( 1 ) 197  2011

  • Time-dependent reliability analysis of existing RC structures in a marine environment using hazard associated with airborne chlorides

    Mitsuyoshi Akiyama, Dan M. Frangopol, Ikumasa Yoshida

    Engineering Structures   32 ( 11 ) 3768 - 3779  2010.11  [Refereed]

     View Summary

    In the design of reinforced concrete (RC) structures in a marine environment, it is important to consider the effects of this environment on structural long-term performance. In this paper, a time-dependent structural reliability analysis method taking the hazard associated with airborne chlorides into consideration is proposed. Also, a procedure to obtain the failure probabilities of RC structures in a marine environment updated by the Sequential Monte Carlo Simulation (SMCS) is indicated. In this procedure, the corrosion crack width and chloride concentration distribution by coring test are used as observational data. For illustrative purposes, time-dependent reliability analyses are presented for one-way RC slabs in a marine environment. Using SMCS, multiple random variables related to observation information can be updated simultaneously. This is realized by taking into consideration the joint probability density functions of the random variables. The effects of various marine environments, inspection results, and number of inspections on the updated estimates of an RC slab reliability are discussed in this paper. © 2010 Elsevier Ltd.

    DOI

  • Time-dependent reliability analysis of existing RC structures in a marine environment using hazard associated with airborne chlorides

    Mitsuyoshi Akiyama, Dan M. Frangopol, Ikumasa Yoshida

    ENGINEERING STRUCTURES   32 ( 11 ) 3768 - 3779  2010.11

     View Summary

    In the design of reinforced concrete (RC) structures in a marine environment, it is important to consider the effects of this environment on structural long-term performance. In this paper, a time-dependent structural reliability analysis method taking the hazard associated with airborne chlorides into consideration is proposed. Also, a procedure to obtain the failure probabilities of RC structures in a marine environment updated by the Sequential Monte Carlo Simulation (SMCS) is indicated. In this procedure, the corrosion crack width and chloride concentration distribution by coring test are used as observational data. For illustrative purposes, time-dependent reliability analyses are presented for one-way RC slabs in a marine environment. Using SMCS. multiple random variables related to observation information can be updated simultaneously. This is realized by taking into consideration the joint probability density functions of the random variables. The effects of various marine environments, inspection results, and number of inspections on the updated estimates of an RC slab reliability are discussed in this paper. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI

  • Stress-averaged strain model for confined high-strength concrete

    Mitsuyoshi Akiyama, Motoyuki Suzuki, Dan M. Frangopol

    ACI Structural Journal   107 ( 2 ) 179 - 188  2010.03  [Refereed]

     View Summary

    When a concrete structure fails, the damage is usually concentrated in a narrow region. The fracture zone and localization behavior have to be captured to accurately assess the structural behavior. In this research, large-scale high-strength reinforced concrete columns were tested under concentric loading. The experimental results show that in columns with sections ranging from 200 to 500 mm (7.88 to 19.7 in.), the length of the compressive fracture zone increases with the cross section dimension; however, the post-peak compressive fracture energies are independent of cross section dimension and column height, provided that the columns have the same concrete compressive strength and lateral confining pressure. A formalized stress-averaged strain model for confined concrete has been developed by using the compressive fracture energy. Regardless of gauge length, cross section dimension, and concrete strength, the proposed model provides good agreement with the test results. © 2010, American Concrete Institute. All rights reserved.

  • Long-term performance prediction of RC bridge slabs in a marine environment

    M. Akiyama, D. M. Frangopol, I. Yoshida

    Bridge Maintenance, Safety, Management and Life-Cycle Optimization - Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Management     3012 - 3019  2010  [Refereed]

     View Summary

    For reinforced concrete (RC) structures located in a marine environment it is important to consider the effects of this environment on their long-term performance. In this paper, a time-dependent structural reliability analysis method of RC bridge slabs taking the hazard associated with airborne chlorides into consideration is proposed. Also, a procedure to obtain the failure probabilities of RC bridge slabs in a marine environment updated by Sequential Monte Carlo Simulation (SMCS) is indicated. Using SMCS, multiple random variables related to observation information can be updated simultaneously. The effects of marine environment, inspection results, and the number of inspections on the updated estimates of bridge slab reliability are discussed. © 2010 Taylor & Francis Group, London.

  • 部分係数を用いた海洋環境下にあるRC構造物の耐久信頼性設計

    松崎裕, 秋山充良, 鈴木基行

    構造工学論文集   56A   733 - 741  2010

  • 炭素繊維シートで被覆した高強度RC杭体の正負交番載荷実験

    阿部遼太, 秋山充良, 佐藤啓, 鈴木基行

    コンクリート工学年次論文報告集   32 ( 2 ) 877 - 882  2010

  • 軸圧縮力と1方向正負交番曲げを受けるスパイラル鋼管の耐震性能とその評価法

    小野潔, 薮本篤, 秋山充良, 大西宵平, 白戸真大, 西村宣男

    土木学会論文集F   66 ( 2 ) 301 - 318  2010

  • 構造物のエネルギー収支に着目した準脆性材料の破壊靭性評価に関する基礎的研究

    車谷麻緒, 湯本達也, 寺田賢二郎, 京谷孝史, 秋山充良

    応用力学論文集   13   313 - 322  2010

  • 塩害環境下にあるコンクリート桁の設計耐用期間にわたる構造安全性評価手法とそのプレテンションPC桁への適用

    松崎裕, 秋山充良, 大木文宏, 中嶋啓太, 鈴木基行

    土木学会論文集E   66 ( 2 ) 147 - 165  2010

  • SMCSを用いたRC構造物劣化度逆推定のための塩化物イオン濃度計測誤差のモデル化

    吉田郁政, 鈴木修一, 秋山充良

    応用力学論文集   13   79 - 88  2010

  • [Keynote Lecture]On life-cycle reliability under earthquake excitations of corroded reinforced concrete structures

    M. Akiyama, Dan M. Frangopol

    IALCCE (International Symposium on Life-Cycle Civil Engineering)    2010

  • Flexural strength of prestressed reinforced concrete piles using high-strength material

    Mitsuyoshi Akiyama, Motoyuki Suzuki, Ryota Abe

    3rd International fib Congress and Exhibition, Incorporating the PCI Annual Convention and Bridge Conference: Think Globally, Build Locally, Proceedings   3   CD - ROM (ID: 17)  2010  [Refereed]

     View Summary

    If concrete bridge systems are constructed in conditions such as very soft soil that can experience soil liquefaction due to a severe earthquake, it is difficult to prevent yielding of the pile foundation. In this study prestressed reinforced concrete pile using high-strength material to increase the pile's flexural capacity is developed. The main structural characteristics of the developed pile are that (1) the neutral axis is constantly near the centroidal axis of the pile, even if longitudinal reinforcements are yielding due to flexural moment, because the pile has a high axial compression force induced by the prestressing steel bars. This means that the concrete in the compression region can contribute to increasing the flexural strength of the pile; and (2) using carbon fiber sheets to prevent the spalling of the cover concrete can contribute to increasing the flexural strength of the pile. The results of the bending test show that the proposed prestressed reinforced concrete pile with carbon fiber sheets and infilling concrete has a higher flexural capacity than that of a pile without these sheets and infilling concrete, and the pile did not exhibit brittle behavior.

  • Reliability estimation for maintenance by sequential monte carlo simulation

    Ikumasa Yoshida, Mitsuyoshi Akiyama, Shuichi Suzuki, Masato Yamagami

    Doboku Gakkai Ronbunshuu A   65 ( 3 ) 758 - 775  2009  [Refereed]

     View Summary

    Inspection or test data of specific site as well as latest knowledge of degrading mechanism should be considered in order to perform accurate reliability estimation of existing structures. This study discusses the methodology to estimate limit state probability updated by inspection or test data. The formulation with sequential Monte Carlo simulation (SMCS) is introduced for updating of model parameters and limit state probability. After demonstrating the solutions by SMCS agrees well with theoretical solutions in a linear Gaussian problem, numerical examples on updating of chloride deterioration parameter of a RC structure and three kind of limit state probability are shown.

    DOI

  • 炭素繊維シートで被覆した高強度RC杭体の単調曲げ載荷実験

    青木直, 秋山充良, 佐藤啓, 鈴木基行

    コンクリート工学年次論文報告集   31 ( 2 ) 553 - 558  2009

  • 公開ハザードを用いたコンクリート構造物の信頼性評価-土木学会コンクリート委員会336委員会活動報告-

    鈴木基行, 秋山充良, 中村 晋, 中村秀明

    コンクリート工学   47 ( 4 ) 21 - 27  2009

    DOI

  • 海洋環境下にあるプレテンションPC 桁の構造信頼性評価

    松崎裕, 中嶋啓太, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   31 ( 1 ) 1009 - 1014  2009

  • コンクリート充填スパイラル鋼管柱の正負交番載荷実験とその耐震性能評価法に関する基礎的研究

    秋山充良, 内藤英樹, 小野潔, 山口恭平, 鈴木基行

    構造工学論文集   55A   662 - 669  2009

  • コンクリート充填スパイラル鋼管柱の一軸圧縮特性および鋼管により横拘束されるコンクリートの平均化応力-ひずみ関係

    秋山充良, 内藤英樹, 小野潔, 白濱永才, 松本大輔, 鈴木基行

    土木学会論文集E   65 ( 4 ) 548 - 563  2009

  • エネルギー収支に基づくコンクリートの破壊靭性評価法に関する基礎的研究

    車谷麻緒, 湯本達也, 寺田賢二郎, 秋山充良

    コンクリート工学年次論文報告集   31 ( 2 ) 97 - 102  2009

  • Sequential Monte Carlo Simulationを用いた維持管理のための信頼性評価手法

    吉田郁政, 秋山充良, 鈴木修一, 山上雅人

    土木学会論文集A   65 ( 3 ) 753 - 775  2009

  • SMCSを用いた既設構造物のための信頼性解析の問題点と精度評価

    吉田郁政, 本城勇介, 秋山充良

    応用力学論文集   12   79 - 88  2009

  • [Keynote Lecture]Seismic Reliability Analysis of Corroded Reinforced Concrete Bridge Piers in a Life-Cycle Perspective

    Dan M. Frangopol, M. Akiyama

    COMPDYN (Computational Methods in Structural Dynamics and Earthquake Engineering)    2009

  • Structural Performance of Deteriorated Concrete Structures :Reliability Approach for Chloride Attack

    Yazuo YAMADA, Mitsuyoshi AKIYAMA, Takumi SHIMOMURA, Shinichi MIYAZATO

      - ( 154 ) 21 - 30  2008.04

  • Seicemic performance of spiral steel pipe piers under cyclic loading

    A. Yabumoto, K. Ono, M. Akiyama, N. Nishimura

    EASEC-11 - Eleventh East Asia-Pacific Conference on Structural Engineering and Construction    2008  [Refereed]

     View Summary

    It has been required to decrease the construction cost of infrastructures. The application of spiral steel pipes to bridge piers is considered as one of the effective methods. Spiral steel pipes are relatively economical because they are produced in large quantities in factories. However roll forming processes of spiral steel pipes are different from those of bending roll pipes which are generally used as bridge piers so that seismic performance of spiral steel pipes may be different from that of bending roll pipes. Therefore it is very important to investigate the ultimate strength and the ductility of spiral steel pipes. In this study in order to grasp the elasto-plastic behavior of spiral steel pipes piers cyclic loading experiments with two specimens were conducted and the effect of radius thickness ratio parameter on the ultimate strength and the ductility was observed. Furthermore the experimental results were compared with the analysis results by the previous seismic evaluation methods.

  • 部分係数を用いた塩害環境下にあるRC構造物の耐久信頼性設計法に関する基礎的研究

    松崎裕, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   30 ( 1 ) 729 - 734  2008

  • 高強度RC杭体へのプレストレス導入による曲げ耐力の改善,

    浅沼大寿, 秋山充良, 佐藤啓, 鈴木基行

    コンクリート工学年次論文報告集   30 ( 3 ) 1003 - 1008  2008

  • 塩害環境下にあるRC橋脚の耐震安全性確保の観点から定めた限界鉄筋腐食量とその耐久設計法に関する確率論的考察

    秋山充良, 松崎裕, 佐藤広和, 内藤英樹, 鈴木基行

    土木学会論文集E   64 ( 4 ) 541 - 559  2008

  • 一軸圧縮を受ける円形CFT柱の力学特性に関する実験的研究

    山口恭平, 秋山充良, 内藤英樹, 鈴木基行

    コンクリート工学年次論文報告集   30 ( 3 ) 1327 - 1332  2008

  • 腐食ひび割れ発生点を限界状態としたRC構造物の耐久信頼性設計に関する基礎的研究

    佐藤広和, 李月鳳, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   29 ( 1 ) 1071 - 1076  2007

  • 一軸圧縮を受けるコンクリート充填鋼管柱で生じる圧縮破壊の局所化

    佐々木健太, 青木峻二, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   29 ( 3 ) 1375 - 1380  2007

  • SRC部材の修復および終局限界状態に対応した変形性能評価法と橋脚の耐震設計への適用

    内藤英樹, 姜一圭, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   29 ( 3 ) 1351 - 1356  2007

  • RC橋脚・杭基礎間に必要な耐力格差に関する確率論的考察

    松崎裕, DANG Tuan Hai, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   29 ( 3 ) 853 - 858  2007

  • Stress-strain behaviour of high-strength concrete columns confined by low-volumetric ratio rectangular ties

    KN Hong, M Akiyama, ST Yi, M Suzuki

    MAGAZINE OF CONCRETE RESEARCH   58 ( 2 ) 101 - 115  2006.03  [Refereed]

     View Summary

    Available test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than 2.0%, are scarce. This paper presents test results loaded in the axial direction for square reinforced concrete (RC) columns confined by various volumetric ratio lateral ties including low volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type and tie volumetric ratio. Local strains are measured using strain gauges bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was improved by changing tie arrangement type from type A to type B. A method to compute the stress in lateral ties at the concrete peak strength is proposed, as well as a new stress-strain model for the confined concrete. The model shows good agreement with stress-strain relationships established experimentally over a wide range of confinement parameters.

    DOI

  • Stress - Strain behaviour of high-strength concrete columns confined by low-volumetric ratio rectangular ties

    K. N. Hong, M. Akiyama, S. T. Yi, M. Suzuki

    Magazine of Concrete Research   58 ( 2 ) 101 - 115  2006.03

     View Summary

    Available test results and stress - strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than 2·0%, are scarce. This paper presents test results loaded in the axial direction for square reinforced concrete (RC) columns confined by various volumetric ratio lateral ties including low volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type and tie volumetric ratio. Local strains are measured using strain gauges bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was improved by changing tie arrangement type from type A to type B. A method to compute the stress in lateral ties at the concrete peak strength is proposed, as well as a new stress - strain model for the confined concrete. The model shows good agreement with stress - strain relationships established experimentally over a wide range of confinement parameters. © 2006 Thomas Telford Ltd.

    DOI

  • High-strength concrete beam without stirrups failed by diagonal tension

    Wei-Lun Wang, Wei-Wen Li, Feng Xing, M. Akiyama, M. Suzuki

    Advances in Structural Engineering:Theory and Applications Vols 1 and 2     1419 - 1424  2006  [Refereed]

     View Summary

    Investigation on high-strength concrete (HSC) beams with concrete compressive strength up to 130MPa is conducted. The results indicate that the increase of shear strength is insignificant with the increase of concrete compressive strength in higher strength ranges than 70MPa;on the contrary,the size effect of HSC beams becomes larger than that of normal strength concrete beams. The shear strength values calculated by current design codes are also compared with the test results to evaluate the precision for HSC beams. It is verified that the shear strength evaluated by many design codes should be unsafe for HSC beams failed by diagonal tension,and the effect of concrete compressive strength and effective depth should be re-estimated.

  • 被災度と関連づけたRC橋梁の損傷確率の評価手法とその適用

    中村晋, 秋山充良, 澤田純男, 安中正, 西岡勉

    地震工学会論文集   6 ( 2 ) 17 - 34  2006

  • 高強度RC柱の圧縮破壊性状に及ぼす供試体断面寸法の影響

    阿部諭史, 秋山充良, 前田直己, 鈴木基行

    コンクリート工学年次論文報告集   28 ( 2 ) 613 - 618  2006

  • 塩害環境下における鉄筋コンクリート構造物の耐久信頼性設計に関する基礎的研究

    秋山充良, 伊東佑香, 鈴木基行

    土木学会論文集E   62 ( 2 ) 385 - 401  2006

  • 一軸圧縮を受ける高強度RC柱の破壊性状および力学的特性に関する研究

    秋山充良, 渡邉正俊, 阿部諭史, 崔松涛, 前田直己, 鈴木基行

    土木学会論文集E   62 ( 3 ) 477 - 496  2006

  • H形鋼の局部座屈に着目したSRC柱の靭性能評価に関する研究

    内藤英樹, 白濱永才, 秋山充良, 高田真人, 鈴木基行

    土木学会論文集E   62 ( 4 ) 698 - 712  2006

  • 3次元FEMモデルを用いたCFT柱における鋼管の局部座屈解析,コンクリート工学年次論文集

    内藤英樹, 松本大輔, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   28 ( 2 ) 1255 - 1230  2006

  • Concentric Loading Test of RC Columns with Normal- and High-Strength Materials and Averaged Stress-Strain Model for Confined Concrete Considering Compressive Fracture Energy

    Suzuki, M, Akiyama, M, Matsuzaki, H, Dang, T. H

    Proceedings of the 2nd fib congress   2   CD  2006

  • Application of Reliability Theory to the Durability-Design of Concrete Structures Subjected to Corrosion

    Akiyama, M, Suzuki, M, Matsuzaki, H, Dang, T. H, nd Li, Y. F

    Proceedings of the 2nd fib congress   2   CD  2006

  • 普通強度から高強度までの構成材料を用いたRC柱の一軸圧縮実験と圧縮破壊エネルギーを介したコンファインドコンクリートの平均化応力-ひずみ関係

    秋山充良, 洪起男, 鈴木将, 佐々木敏幸, 前田直己, 鈴木基行

    土木学会論文集   No. 788/V-67   81 - 98  2005

  • 耐久設計に用いる塩害劣化作用の確率モデルに関する基礎的研究

    伊東佑香, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   27 ( 2 ) 1477 - 1482  2005

  • 正負交番荷重を受けるSRC 柱の塑性曲率分布のモデル化および軸方向鉄筋の座屈に着目した靭性能評価

    内藤英樹, 秋山充良, 高田真人, 清水真介, 洪起男, 鈴木基行

    構造工学論文集   51A   1415 - 1424  2005

  • 構造物の損傷度および損傷度曲線の評価手法に関する一考察

    中村晋, 秋山充良, 澤田純男, 西岡勉

    土木学会地震工学論文集   28  2005

  • 一軸圧縮を受ける高強度RC円柱で生じる圧縮破壊の局所化

    佐々木敏幸, 秋山充良, 前田直己, 鈴木基行

    コンクリート工学年次論文報告集   27 ( 2 ) 697 - 702  2005

  • RC橋梁の被災度と関連づけられた損傷確率の評価手法に関する一考察

    中村晋, 秋山充良, 澤田純男, 安中正, 西岡勉

    応用力学論文集   8   693 - 700  2005

  • 多点荷重を受けるRCはりのせん断耐力評価に関する研究

    齊藤啓一, 高橋宏幸, 石橋忠良, 丸山久一, 秋山充良, 鈴木基行

    土木学会論文集   No. 767/V-64   87 - 98  2004

  • 高強度構成材料を用いたRC柱の一軸圧縮実験とその横拘束モデルに関する研究

    秋山充良

    コンクリート工学   42 ( 4 ) 58 - 64  2004

  • 確率的地震ハザード解析結果を反映したRC橋脚の耐震設計に用いる安全係数と設計地震力の設定の試み

    秋山充良, 野口文孝, 伊藤佑香, 鈴木基行

    コンクリート工学年次論文報告集   26 ( 2 ) 1147 - 1152  2004

  • 一軸圧縮を受ける高強度RC柱の破壊性状に関する一考察

    洪起男, 秋山充良, 前田直己, 鈴木基行

    コンクリート工学年次論文報告集   26 ( 2 ) 793 - 798  2004

  • 一軸圧縮を受ける高強度RC柱における横拘束筋の拘束効果と応力-ひずみ関係の定式化に関する実験的研究

    秋山充良, 洪起男, 佐藤成禎, 鈴木将, 前田直己, 鈴木基行

    土木学会論文集   No. 753/V-62   137 - 151  2004

  • コンクリート圧縮強度130N/mm2・せん断補強鉄筋降伏強度1200N/mm2までを用いたRCはりのせん断耐力算定式

    秋山充良, 王衛侖, 前田直己, 鈴木基行

    構造工学論文集   50A   907 - 917  2004

  • Evaluation of seismic performance of RC bridge piers based on reliability theory in consideration of structural system

    Mitsuyoshi Akiyama, Motoyuki Suzuki

    Proceedings of the fib Symposium 2003: Concrete Structures in Seismic Regions     442 - 443  2003  [Refereed]

  • 有効高さが変化するRC棒部材のせん断耐力評価に関する実験的研究

    齊藤啓一, 石橋忠良, 井料青海, 武田三弘, 秋山充良, 鈴木基行

    土木学会論文集   Vol.725/V-58   71 - 83  2003

  • 軸方向鉄筋を多段に配置したディープビームのせん断耐力評価に関する実験的研究

    齋藤啓一, 田中勝俊, 石橋忠良, 寺田年夫, 秋山充良, 鈴木基行, 今井昌文

    土木学会論文集   No.746/V-61   181 - 195  2003

  • 軸方向鉄筋の座屈発生点に対応した終局曲率の簡易算定法およびRC柱とSRC柱の靭性能評価への適用

    秋山充良, 内藤英樹, 鈴木基行

    土木学会論文集   Vol. 725/V-58   113 - 129  2003

  • 軸方向鉄筋の座屈を考慮したRC柱とSRC柱の履歴復元力モデル

    内藤英樹, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   25 ( 2 ) 1189 - 1194  2003

  • レベル2地震動を受ける水道用PCタンク杭基礎の耐震性能照査法に関する基礎的研究

    野口文孝, 秋山充良, 西尾浩志, 鈴木基行

    コンクリート工学年次論文報告集   25 ( 2 ) 1243 - 1248  2003

  • プレストレストコンクリート製タンク側壁のレベル2地震動に対する耐震性能照査

    西尾浩志, 横山博司, 秋山充良, 小野雄司, 江角真也, 鈴木基行

    土木学会論文集   Vol.725/V-58   85 - 100  2003

  • コンクリート構造物の信頼性設計法に関する研究

    秋山充良

    コンクリート工学   41 ( 6 ) 61 - 66  2003

  • コンクリート圧縮強度130MPaまでを対象とした腹鉄筋のないRCはりのせん断強度式

    鈴木基行, 秋山充良, 王衛侖, 佐藤成禎, 前田直己, 藤澤豊

    土木学会論文集   No.739/V-60   75 - 91  2003

  • RC構造物の耐震安全性に影響する不確定要因の抽出

    秋山充良, 丸山大輔, 鈴木基行

    コンクリート工学年次論文報告集   25 ( 2 ) 1177 - 1182  2003

  • 地震動の位相特性のばらつきがRC橋脚の弾塑性応答に与える影響

    丸山大輔, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   24 ( 2 ) 1009 - 1014  2002

  • 早強性混和材を使用したコンクリートの強度発現メカニズム

    佐藤誠, 米田正彦, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   24 ( 1 ) 267 - 272  2002

  • 軸方向鉄筋の非弾性座屈解析に基づく単柱式RC橋脚の終局変位算定法

    内藤英樹, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   24 ( 2 ) 991 - 996  2002

  • 構造系の信頼性を考慮したRC橋脚の耐震設計に用いる安全係数の試算

    秋山充良, 土井充, 松中亮治, 鈴木基行

    土木学会論文集   Vol.718/V-57   1 - 17  2002

  • Seismic Safety Evaluation of Prestressed Concrete Tank in Consideration of Level II Earthquake Motions

    Motoyuki Suzuki, Hiroshi Nishio, Kazuma Omura, Mitsuyoshi Akiyama, Shinya Esumi

    Proceedings of the 1st fib congress   1   CD  2002

  • Reliability-Based Optimal Design in Consideration of Structural System and Its Application to Evaluation of Seismic Performance of RC Bridge Piers

    Mitsuyoshi AKIYAMA, Ryoji MATSUNAKA, Mitsuru DOI, Motoyuki SUZUKI

    Concrete Library of JSCE   39   65 - 88  2002

  • Proposal of the Partial Safety Factors for Seismic Design of Concrete Structures in Consideration of Reliability Theory and Optimization of Structural Systems

    Mitsuyoshi Akiyama, Motoyuki Suzuki, Daisuke Maruyama, Hong Kee Nam

    Proceedings of the 1st fib congress   1   CD  2002

  • Ductility Design of Concrete Encased Steel Piers

    Hideki Naito, Mitsuyoshi Akiyama, Motoyuki Suzuki

    Proceedings of the 1st fib congress   1   CD  2002

  • 静的非線形解析に基づくSRCラーメン橋脚の耐震設計法に関する研究

    内藤英樹, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   23 ( 3 ) 1261 - 1266  2001

  • 構造系信頼性評価法と構造最適化手法を用いたRC橋脚と場所打ち杭基礎間の耐力階層化に関する基礎的研究

    秋山充良, 松中亮治, 土井充, 鈴木基行

    構造工学論文集   47A   743 - 752  2001

  • 繰返し荷重を受けるSRC柱の荷重-変位関係に関する解析的研究

    秋山充良, 林寛之, 内藤英樹, 鈴木基行

    構造工学論文集   47A   1453 - 1463  2001

  • レベル2地震動を考慮したプレストレストコンクリート製タンクの耐震安全性評価

    小林寛明, 西尾浩志, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   23 ( 3 ) 1147 - 1152  2001

  • Method of Evaluating Earthquake Safety of RC Bridge System Based on Reliability Theory

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Yasunori YAMAZAKI, Ryoji MATSUNAKA, Mitsuru DOI

    Concrete Library of JSCE   38   33 - 50  2001

  • A Proposal for the Rational Seismic Design of RC 2-Story Rigid-Frame Viaducts in Consideration of the Yield Process

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Shinsuke TANAKA, Takamichi MARUNAKA

    Concrete Library of JSCE   37   17 - 29  2001

  • 鉄筋コンクリート橋梁システムに介在する不確定要因を考慮した場所打ち杭基礎の設計水平震度評価に関する研究

    秋山充良, 松中亮治, 土井充, 鈴木基行

    土木学会論文集   No.641/V-46   187 - 203  2000

  • 信頼性理論を用いた構造最適設計手法の提案およびRC橋脚の耐震安全性評価への適用

    秋山充良, 松中亮治, 土井充, 鈴木基行

    土木学会論文集   No.662/V-49   185 - 204  2000

  • 信頼性理論に基づくRC橋梁システムの地震時安全性評価法

    鈴木基行, 秋山充良, 山崎康紀, 松中亮治, 土井充

    土木学会論文集   No.648/V-47   9 - 21  2000

  • 信頼性理論と構造最適化手法を用いた連続ラーメン橋の橋脚躯体の耐震設計

    秋山充良, 松中亮治, 町 勉, 鈴木基行

    コンクリート工学年次論文報告集   22 ( 3 ) 1297 - 1302  2000

  • 簡便なせん断補強筋機械式継手の開発およびそのRC部材への適用に関する実験的研究

    鈴木基行, 秋山充良, 杉田稔, 松山英雄, 宇田川亮

    コンクリート工学論文集   11 ( 3 ) 49 - 61  2000

  • Influence of Correlations between Structural Variables on the Seismic Safety of RC Bridge Piers

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Yasunori YAMAZAKI, Ryoji MATSUNAKA

    Concrete Library OF JSCE   35   119 - 133  2000

  • 部材の降伏過程がRC2層ラーメン高架橋の応答変位に及ぼす影響

    鈴木基行, 秋山充良, 田中慎介, 丸中孝通, 浮本忍

    構造工学論文集   45A   1359 - 1367  1999

  • 信頼性理論に基づくRC橋脚-杭基礎間の地震時損傷配分に関する研究

    土井 充, 山崎康紀, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   21 ( 3 ) 1285 - 1290  1999

  • 降伏過程を考慮したRC2層ラーメン高架橋の合理的耐震設計法の提案

    鈴木基行, 秋山充良, 田中慎介, 丸中孝通

    土木学会論文集   No.634/V-45   269 - 278  1999

  • 構造変数間の相関がRC橋脚の耐震安全性に及ぼす影響

    鈴木基行, 秋山充良, 山崎康紀, 松中亮治

    土木学会論文集   No. 620/V-43   175 - 185  1999

  • RC2層ラーメン構造物の合理的耐震設計法の提案

    秋山充良, 田中慎介, 丸中孝通, 鈴木基行

    コンクリート工学年次論文報告集   21 ( 3 ) 1225 - 1230  1999

  • 相関を考慮した信頼性理論に基づくRC橋脚の地震時安全性評価法に関する研究

    松中亮治, 山崎康紀, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   20 ( 3 ) 979 - 984  1998

  • RC2層ラーメン高架構造の地震応答に及ぼす軸方向およびせん断補強鉄筋比の影響

    鈴木基行, 砂金伸治, 秋山充良, 田中慎介

    構造工学論文集   44A   1401 - 1412  1998

  • Safety Evaluation Method of Structural System and Its Application to Seismic Design of RC Bridge Pier

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Yasunori YAMAZAKI

    Concrete Library of JSCE   32   43 - 68  1998

  • 信頼性理論に基づく橋梁システムの地震時安全性評価法に関する研究

    山崎康紀, 松中亮治, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   21 ( 3 ) 1279 - 1284  1997

  • 信頼性理論に基づくRC橋脚の地震時安全性評価法に関する研究

    山崎康紀, 秋山充良, 鈴木基行

    コンクリート工学年次論文報告集   19 ( 2 ) 441 - 446  1997

  • 構造系の安全性評価法およびRC橋脚の耐震設計への適用に関する研究

    鈴木基行, 秋山充良, 山崎康紀

    土木学会論文集   No.578/V-37   71 - 87  1997

▼display all

Books and Other Publications

  • Structural Deterioration Mechanisms

    Akiyama, M, Soliman, M, Biondini, F, Frangopol, D.M( Part: Joint author)

    American Society of Civil Engineers  2019

  • 南海トラフ地震 その防災と減災を考える

    秋山 充良( Part: Joint author)

    早稲田大学出版部  2019

  • Reliability-based durability design and service life assessment of concrete structures in an aggressive environment

    Akiyama, M, Frangopol, D.M, Matsuzaki, H

    CRC Press/Balkema  2014

  • Computational Methods in Earthquake Engineering

    Dan M. Frangopol, M. Akiyama

    Springer  2010

Misc

  • Life-cycle reliability-based design and reliability updating of reinforced concrete shield tunnels in coastal regions

    Zheng Shu He, Srivaranun Supasit, Mitsuyoshi Akiyama, Dan M. Frangopol

    Structure and Infrastructure Engineering   16 ( 4 ) 726 - 737  2020.04  [Refereed]

     View Summary

    In this paper, a novel approach for life-cycle reliability-based design and reliability updating of reinforced concrete (RC) shield tunnels in coastal regions has been developed. For new shield tunnels, a reliability-based durability design criterion to determine the concrete cover and concrete quality for preventing the deterioration of structural performance during the structural service life is proposed. For existing shield tunnels, an approach to update structural reliability is established based on Sequential Monte Carlo Simulation. Epistemic uncertainty associated with the structural performance prediction of existing shield tunnels can be reduced compared with that of new shield tunnels. In illustrative examples, durability design factors and maximum water to cement ratio for designing RC segment satisfying the target durability reliability are investigated. For existing RC shield tunnels, the effect of the observational deformation of segmental lining on the time-dependent failure probability is discussed.

    DOI

  • コンクリート構造物の安全確保のためのシステムに関する研究小委員会成果報告書

    鎌田敏郎, 国枝稔, 秋山充良, 浅本晋吾, 大島義信, 服部晋一, 三木朋広, 山村正人, 石田雅博, 今井卓也, 稲葉尚文, 岩波光保, 笠井尚哉, 小林薫, 佐藤靖彦, 竹田宣典, 長縄卓夫, 福永靖雄, 堀倫裕, 松田浩, 森雅司

    コンクリート技術シリーズ   ( 108 )  2015

    J-GLOBAL

  • 示方書連絡調整小委員会報告書-次世代の「コンクリート標準示方書」に向けて-

    佐藤靖彦, 秋山充良, 石田哲也, 伊代田岳史, 加藤佳孝, 斉藤成彦, 牧剛史, 山本貴士, 浅田尚, 浅本晋吾, 阿波稔, 岩波光保, 上田隆雄, 上田尚史, 上田洋, 臼井達哉, 大島正記, 片健一, 加藤絵万, 国枝稔, 蔵重勲, 古賀裕久, 小林孝一, 齋藤隆, 坂井吾郎, 坂口淳一, 佐川康貴, 桜井邦昭, 塩畑英俊, 田所敏弥, 田中博一, 田中泰司, 千々和伸浩, 築嶋大輔, 土屋智史, 長井宏平, 半井健一郎, 西田孝弘, 日比野誠, HENRY Michael

    コンクリート技術シリーズ   ( 107 )  2015

    J-GLOBAL

  • Damage of Bridges during 2011 Great East Japan Earthquake

    KAWASHIMA Kazuhiko, KOSA Kenji, TAKAHASHI Yoshikazu, AKIYAMA Mitsuyoshi, NISHIOKA Tsutomu, WATANABE Gakuho, KOGA Hirohisa, MATSUZAKI Hiroshi

    Proc Jt Meet U S Jpn Panel Wind Seism Eff UJNR   43rd   165 - 178  2012

    J-GLOBAL

  • Size effect on compressive fracture behavior of RC column with high-strength materials

    Satoshi Abe, Mitsuyoshi Akiyama, Motoyuki Suzuki

    Journal of Structural Engineering   57A   386 - 394  2011

  • Reliability-based durability design for RC structures in a marine environment based on the partial factors format

    Hiroshi Matsuzaki, Mitsuyoshi Akiyama, Motoyuki Suzuki

    Journal of Structural Engineering   56 ( A ) 733 - 741  2010

  • A method for structural reliability analysis of concrete beams under marine environment over lifetime and its application to pretensioned PC beams

    Hiroshi Matsuzaki, Mitsuyoshi Akiyama, Fumihiro Ohki, Keita Nakajima, Motoyuki Suzuki

    Journal of the JSCE E   66 ( 2 ) 147 - 165  2010

    DOI

  • CYCLIC LOADING TEST OF HIGH STRENGTH CONCRETE PILE WITH CARBON FIBER SHEET

    Ryota ABE, Mitsuyoshi AKIYAMA, Kei SATOH, Motoyuki SUZUKI

    Proc. of the JCI   32 ( 2 ) 877 - 882  2010

  • Seismic performance evaluation of concrete filled spiral steel tubes based on reversal cyclic loading tests

    Mitsuyoshi Akiyama, Hideki Naito, Kiyoshi Ono, Kyohei Yamaguchi, Motoyuki Suzuki

    Journal of Structural Engineering   55A   662 - 669  2009

  • Structural Reliability Analysis of Pretensioned Prestressed Concrete Beam in the Marine Environment

    Hiroshi MATSUZAKI, Keita NAKAJIMA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   31 ( 1 ) 1009 - 1014  2009

  • Monotonic Bending Load Tests of High Strength RC Piles with Carbon Fiber Sheets

    Nao AOKI, Mitsuyoshi AKIYAMA, Kei SATO, Motoyuki SUZUKI

    Proc. of the JCI   31 ( 2 ) 553 - 558  2009

  • Reliability Analysis of an Existing RC Structure Updated by Inspection Data

    I. Yoshida, M. Akiyama, M. Suzuki

    Proceedings of the Tenth International Conference on Structural Safety and Reliability     2482 - 2489  2009

  • CONCRETE LOADING TESTS OF CONCRETE FILLED SPIRAL STEEL TUBES AND STRESS-STRAIN RELATION OF CONCRETE CONFINED BY STEEL TUBES

    Mitsuyoshi AKIYAMA, Hideki NAITO, Kiyoshi ONO, Nobutaka SHIRAHAMA, Daisuke MATSUMOTO, Motoyuki SUZUKI

    Journal of the JSCE E   65 ( 4 ) 548 - 563  2009

    DOI

  • コンクリート構造物の信頼性設計法に関する研究小委員会(336委員会)成果報告書

    秋山充良, 中村晋, 中村秀明, 松島学, 宮川義範, 吉田郁政, 吉見雅行, 安中正, 岩波基, 加藤佳孝, 河野哲也, 斉藤成彦, 篠田昌弘, 下村匠, 鈴木修一, 堤英明, 西山誠治, 花岡大伸, 松崎裕, 松本敏克, 高橋順, 松久保博敬, 寺村悟

    コンクリート技術シリーズ   ( 83 ) 352P  2008.12

    J-GLOBAL

  • Mechanical properties of circular CFT columns under concentric compression

    Kyohei YAMAGUCHI, Mitsuyoshi AKIYAMA, Hideki NAITO, Motoyuki SUZUKI

    Proc. of the JCI   30 ( 3 ) 1327 - 1332  2008

  • Use of prestressing to improve load bearing capacity of RC piles with high-strength materials

    Taiju ASANUMA, Mitsuyoshi AKIYAMA, Kei SATO, Motoyuki SUZUKI

    Proc. of the JCI   30 ( 3 ) 1003 - 1008  2008

  • Reliability-based durability design of RC structures under marine environments using partial factors

    Hiroshi MATSUZAKI, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   30 ( 1 ) 729 - 734  2008

  • MAXIMUM AMOUNT OF REINFORCING BAR CORROSION AND RELIABILITY-BASED DURABILITY DESIGN TO ENSURE THE SEISMIC SAFETY OF RC BRIDGE PIERS EXPOSED TO MARINE ENVIRONMENT

    Mitsuyoshi AKIYAMA, Hiroshi MATSUZAKI, Hirokazu SATO, Hideki NAITO, Motoyuki SUZUKI

    Doboku Gakkai Ronbunshuu E   64 ( 4 ) 541 - 559  2008

    DOI

  • 地震時損傷確率を判断基準としたRC橋脚・杭基礎間の耐力階層化に関する一考察

    松崎裕, Dang Tuan Hai, 秋山充良, 鈴木基行

    JCOSSAR2007論文集     293 - 298  2007

  • Reliability-Based Design of Reinforced Concrete Structures with Corrosion-Initiated Cracking

    Hirokazu SATO, Yuefeng LI, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   29 ( 1 ) 1071 - 1076  2007

  • Seismic Design of SRC Piers Considering Restorability and Ultimate State of Members

    Hideki NAITO, Il-gu KANG, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   29 ( 3 ) 1351 - 1356  2007

  • Localized Compression Failure Zone of Concrete Filled Steel Tubular Columns

    Kenta SASAKI, Shunji AOKI, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   29 ( 3 ) 1375 - 1380  2007

  • Reliability-Based Demanded Capacity Hierarchy between RC Bridge Pier and Pile Foundation

    Hiroshi MATSUZAKI, DANG Tuan Hai, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   29 ( 3 ) 853 - 858  2007

  • Effect of Shape Size of Specimen on Mechanical Properties of High Strength Confined Concrete

    Satoshi, ABE, Mitsuyoshi AKIYAMA, Naomi MAEDA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   28 ( 2 ) 613 - 618  2006

  • Ductility Ealuation of SRC Columns Estimating the Local Buckling of the H-Shaped Steel

    Hideki NAITO, Nobutaka SHIRAHAMA, Mitsuyoshi AKIYAMA, Masato TAKADA, Motoyuki SUZUKI

    Proc. of JSCE   62 ( 4 ) 698 - 712  2006

    DOI

  • Reliability-Based Durability Design of Reinforced Concrete Structures Exposed to Marine Environments

    Mitsuyoshi AKIYAMA, Yuka ITO, Motoyuki SUZUKI

    Proc. of JSCE   62 ( 2 ) 385 - 401  2006

    DOI

  • Study on the evaluation of fragility characteristics associated with damage degree of RC bridge system and its application

    Susumu NAKAMURA, Mitsuyoshi AKIYAMA, Sumio SAWADA, Tadashi AN-NAKA, Tsutomu NISHIOKA

    Journal of JAEE   6 ( 2 ) 17 - 34  2006

  • Compressive Fracture Behavior and Mechanical Properties of RC Columns with Normal- and High-Strength Materials under Concentric Compression

    Mitsuyoshi AKIYAMA, Masatoshi WATANABE, Satoshi ABE, Song Tao CUI, Naomi MAEDA, Motoyuki SUZUKI

    Proc. of JSCE   62 ( 3 ) 477 - 496  2006

    DOI

  • Local Buckling Analysis of Steel Tube of Concrete-Filled Steel Tube Columns

    Hideki, NAITO, Daisuke MATSUMOTO, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   28 ( 2 ) 1255 - 1260  2006

  • Study on the Evaluation of Fragility Characteristics Associated with Damage Degree of RC Bridge System

    Susumu NAKAMURA, Mitsuyoshi AKIYAMA, Sumio SAWADA, Tadashi AN-NAKA, Tsutomu NISHIOKA

    Journal of Applied Mechanics   8  2005

  • Modeling of plastic curvature distribution of SRC columns subjected to reversal cyclic loading and its application to ductility evaluation of columns predicting buckling of longitudinal bars

    Hideki NAITO, Mitsuyoshi AKIYAMA, Masato TAKADA, Shinsuke SHIMIZU, Kee-Nam HONG, Motoyuki SUZUKI

    Journal of Structural Engineering, JSCE   51A   1415 - 1424  2005

  • Localized Compression Failure Zone of High-Strength RC Columns under Uniaxial Compression

    Toshiyuki SASAKI, Mitsuyoshi AKIYAMA, Naomi MAETA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   27 ( 2 ) 697 - 702  2005

  • A Study on Probabilistic Model of a Chloride Attack for Durability Design of Reinforced Concrete Structures

    Yuka ITO, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   27 ( 2 ) 1477 - 1482  2005

  • Study on the Evalution of Damage Degree and Fragility Curve for Structure

    Susumu NAKAMURA, Mitsuyoshi AKIYAMA, Sumio SAWADA, Tsutomu NISHIOKA

    Journal of Earthquake Engineering, JSCE   28   CD-ROM(#034)-  2005

  • Reliability-Based Seismic Design of RC Piers Based on Probabilistic Seismic Hazard Analysis

    Mitsuyoshi AKIYAMA, Fumitaka NOGUCHI, Yuka ITO, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   26 ( 2 ) 1147 - 1152  2004

  • The Shear Strength of Reinforced Concrete Beams under Multiple Points Load

    Keiichi SAITO, Hiroyuki TAKAHASHI, Tadayoshi ISHIBASHI, Kyuuichi MARUYAMA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of JSCE   ( 767 ) 87 - 98  2004

    DOI

  • Eefect of Transverse Reinforcement on Behavior of High Strength Concrete Columns Under Concentric Compression and Its Modeling of Stress-Strain Relationship

    Mitsuyoshi AKIYAMA, Kee-Nam HONG, Masayoshi SATO, Masaru SUZUKI, Naomi MAEDA, Motoyuki SUZUKI

    Pro. of JSCE   ( 753 ) 137 - 151  2004

    DOI

  • Experimental Study on Behavior of High-Strength Concrete Columns under Concentric Compression

    Kee-Nam HONG, Mitsuyoshi AKIYAMA, Naomi MAEDA, Motoyuki SUZUKI

    Proceedings of the Japan Concrete Institute   26 ( 2 ) 793 - 798  2004

  • Shear Strength of Reinforced Concrete Linear Members with Variable Effective Depth

    Keiichi SAITO, Tadayoshi ISHIBASHI, Omi IRYO, Mitsuhiro TAKEDA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of JSCE   ( 725 ) 71 - 83  2003

    DOI

  • Calculation Method of Ultimate Curvature of RC and SRC Section Based on Analytical Model for Axial Reinforcement Buckling and Its Application to Ductility Evaluation of These Columns

    Mitsuyoshi AKIYAMA, Hideki NAITO, Motoyuki SUZUKI

    Proc. of JSCE   ( 725 ) 113 - 129  2003

    DOI

  • Seismic Design of Prestressed Concrete Tank Pile Foundations Subjected to Level II Earthquake Motion

    Fumitaka NOGUCHI, Mitsuyoshi AKIYAMA, Hiroshi NISHIO, Motoyuki SUZUKI

    Proc. of the JCI   25 ( 2 ) 1243 - 1248  2003

  • Strength of Reinforced Deep Beams with Multiple Layers of Longitudinal Bars

    Kiichi SAITO, Katsutohi TANAKA, Tadayoshi ISHIBASHI, Toshio TERADA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI, Masafumi IMAI

    Proc. of JSCE   ( 746 ) 181 - 195  2003

    DOI

  • Uncertainties Affecting the Seismic Reliability of RC Structures

    Mitsuyoshi AKIYAMA, Daisuke MARUYAMA, Motoyuki SUZUKI

    Proc. of the JCI   25 ( 2 ) 1177 - 1182  2003

  • Hysteresis Model of RC and SRC Columns Considering the Buckling of Bars

    Hideki NAITO, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   25 ( 2 ) 1189 - 1194  2003

  • Seismic Performance Evaluation for Side Wall of Prestressed Concrete Tank Subjected to Level II Earthquake Motions

    Hiroshi NISHIO, Hiroshi YOKOYAMA, Mitsuyoshi AKIYAMA, Yuji ONO, Shinya ESUMI, Motoyuki SUZUKI

    Proc. of JSCE   ( 725 ) 85 - 100  2003

    DOI

  • Shear Strength of RC Beams without Stirrup Using High-Strength Concrete of Compressive Strength Ranging to 130 MPa

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Wei Lun WANG, Masayoshi SATO, Naomi MAEDA, Yutaka FUJISAWA

    Proc. of JSCE   ( 739 ) 75 - 91  2003

    DOI

  • Mechanisms of Strength Development of Concrete Incorporating Accelerating Admixture

    Makoto SATO, Masahiko MAITA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   24 ( 1 ) 267 - 272  2002

  • Effect of Phase Characteristics of Ground Motions on the Seismic Response of RC Bridge Piers

    Daisuke MARUYAMA, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   24 ( 2 ) 1009 - 1014  2002

  • Safety Factors for Seismic Design of RC Bridge Piers in Consideration of System Reliability

    Mitsuyoshi AKIYAMA, Mitsuru DOI, Ryoji MATSUNAKA, Motoyuki SUZUKI

    Proc. of JSCE   ( 718 ) 1 - 17  2002

    DOI

  • Ductility Design of Reinforced Concrete Piers Based on Non-Linear Buckling Analysis of Bars

    Hideki NAITO, Mitsuyoshi AKIYAMA, Motoyuki SUZUKI

    Proc. of the JCI   24 ( 2 ) 991 - 996  2002

  • Seismic Safety Evaluation of Prestressed Concrete Tank in Consideration of Level 2 Earthquake Motion

    H. Kobayashi, K. Nishio, M. Akiyama, M. Suzuki

    Proc. of the JCI   23 ( 3 ) 1147 - 1152  2001

  • Evaluation of Horizontal Seismic Coefficient for Cast in Place Pile Using Reliability-Based Optimal Design Considering Structural System

    Mitsuyoshi AKIYAMA, Ryoji MATSUNAKA, Mitsuru DOI, Motoyuki SUZUKI

    Journal of Structural Engineering   47A   743 - 752  2001

  • Analytical Study on Load-Deflection Characteristics of Concrete Encased Steel Columns Subjected to Reversal Cyclic Loading

    Mitsuyoshi AKIYAMA, Hiroyuki HAYASHI, Hideki NAITO, Motoyuki SUZUKI

    Journal of Structural Engineering   47A   1453 - 1463  2001

  • Study on Ductility Design of Concrete Encased Steel Frame Piers

    H. Naito, M. Akiyama, M. Suzuki

    Proc. of the JCI   23 ( 3 ) 1261 - 1266  2001

  • Reliability-Based Optimal Design Considering Structural System and Its Application to Evaluation of Seismic Performance of RC Bridge Pier

    Mitsuyoshi AKIYAMA, Ryoji MATSUNAKA, Mitsuru DOI, Motoyuki SUZUKI

    Proc. of JSCE   ( 662 ) 185 - 204  2000

    DOI

  • SAFETY EVALUATION METHOD OF RC BRIDGE SYSTEMS UNDER EARTHQUAKE BASED ON RELIABILITY THEORY

    鈴木基行, 秋山充良, 山崎康紀, 松中亮治, 土井 充

    Proc. of JSCE   ( 648 ) 9 - 21  2000

    DOI

  • Development of Simple Mechanical Splice for Shear Reinforcement and Experimental Study on Its Application to RC Members

    Motoyuki SUZUKI, Mitsuyoshi AKIYAMA, Minoru SUGITA, Hideo MATSUYAMA, Akira UDAGAWA

    Concrete Research and Technology   11 ( 3 ) 49 - 61  2000

  • EVALUATION OF HORIZONTAL SEISMIC COEFFICIENT FOR CAST IN PLACE PILE UNDER THE CONSIDERATION OF UNCERTAINTIES IN REINFORCED CONCRETE BRIDGE SYSTEMS

    秋山充良, 松中亮治, 土井充, 鈴木基行

    Proc. of JSCE   ( 641 ) 187 - 203  2000

    DOI

  • PROPOSAL OF SEISMIC DESIGN METHOD OF RC 2-STORY VIADUCT CONSIDERING THE YIELD PROCESS

    鈴木基行, 秋山充良, 田中慎介, 丸中孝通

    PROC. OF JSCE   ( 634 ) 269 - 278  1999

    DOI

  • Safety Evaluation Method of RC-Bridge Pier under Earthquake Based on Reliability Theory

    Y. Yamazaki, M. Akiyama, M. Suzuki

    Proc. of the JCI   19 ( 2 ) 441 - 446  1997

  • Safety Evaluation Method of Structural System and Its Application to Seismic Design of RC Bridge Pier

    M. Suzuki, M. Akiyama, Y. Yamazaki

    Proc. of JSCE   578 ( V-37 ) 71 - 87  1997

    DOI

▼display all

Works

  • 点検・検査の結果を利用した劣化構造物のライフタイム評価に対する確率論的アプローチ

    2008
    -
    2009

  • 点検・検査の結果を利用した劣化構造物のライフタイム評価に対する確率論的アプローチ

    2008
    -
    2009

  • 地震リスク最小化を可能にする鋼コンクリート複合構造形式の検討

    2007
    -
    2009

  • 地震リスク最小化を可能にする鋼コンクリート複合構造形式の検討

    2007
    -
    2009

  • コンクリート充填鋼管杭を橋脚に利用した乗用車専用道路の開発

    2006
    -
    2007

  • コンクリート充填鋼管杭を橋脚に利用した乗用車専用道路の開発

    2006
    -
    2007

  • 高強度構成材料を用いたRC耐震部材の開発と信頼性理論に基づくその性能向上度の定量化

    2005
    -
    2007

  • 高強度構成材料を用いたRC耐震部材の開発と信頼性理論に基づくその性能向上度の定量化

    2005
    -
    2007

  • 超高性能耐震部材の開発と確率論的損傷評価手法によるその性能照査

    2004
    -
    2005

  • 超高性能耐震部材の開発と確率論的損傷評価手法によるその性能照査

    2004
    -
    2005

  • RC橋脚の耐震設計に用いる安全係数

    2000
    -
    2001

  • Safety Factors for Seismic Design of RC Bridge Piers

    2000
    -
    2001

  • RC橋脚の耐震設計に用いる安全係数

    2000
    -
    2001

  • RC橋脚の耐震設計に用いる安全係数

    2000
    -
    2001

  • PCタンクの耐震安全性評価

    1999
    -
    2001

  • PCタンクの耐震安全性評価

    1999
    -
    2001

  • 橋脚の保有耐力を考慮した杭基礎の設計水平震度算定に関する確率的考察

    1999
    -
    2000

  • 橋脚の保有耐力を考慮した杭基礎の設計水平震度算定に関する確率的考察

    1999
    -
    2000

  • 橋脚の保有耐力を考慮した杭基礎の設計水平震度算定に関する確率的考察

    1999
    -
    2000

  • Evaluation of Horizontal Seismic coeffieat for Cast in Place Pile under the consideration of Uncertainties in RC Bridge Piers

    1999
    -
    2000

▼display all

Awards

  • Junior Research Prize

    2016.06   IABMAS  

    Winner: AKIYAMA, Mitsuyoshi

  • 第56回構造工学シンポジウム論文賞

    2010.06  

  • 平成21年度土木学会吉田賞(論文部門)

    2010.05  

  • 科学技術分野の文部科学大臣表彰 若手科学者賞

    2008.05  

  • 平成18年度土木学会論文奨励賞

    2007.05  

  • 平成18年度土木学会吉田賞(論文部門)

    2007.05  

  • 第50回構造工学シンポジウム論文賞

    2004.05  

  • 平成13年日本コンクリート工学協会賞(技術賞)

    2001.05  

  • 平成9年度土木学会吉田賞(論文部門)

    1998.05  

▼display all

Research Projects

  • レジリエンス強化のための備災マネジメントと南海トラフ地震・津波の影響地域への適用

    Project Year :

    2019.04
    -
    2023.03
     

  • 将来の設計地震力増大に対応できるメタボリズム耐震橋脚構造の開発

    Project Year :

    2018.04
    -
    2022.03
     

  • 「危機耐性」の概念に基づく耐震設計体系の確立と実現のための要素技術の開発

    Project Year :

    2016.04
    -
    2020.03
     

     View Summary

    危機耐性の設計概念を整理した.これまでの検討に基づき,ストレステストのための仮想的外力としての地震動や,コミュニティと技術者の情報共有を促す体系の重要性について整理した.また,共有情報のマネジメントとしてリスクガバナンスが重要であること等を示した.強震動地震動のシミュレーションのためのモデル化について特性震源化モデルを対象として検討するとともに,断層変位に対して危機耐性を確保する方策に関する調査研究を実施するための産学官の専門家による検討会を発足させた.耐震構造については,まず,摩擦振子型免震機構を有するRC橋脚について,H28の震動実験結果を受け,改良を試みた.まず,滑り面形状の工夫による滑り性能の改善,および,表面強化材の塗布による滑り面の耐摩耗性の向上を図り,水平二方向震動実験によりその効果を確認した.特に,3Dプリンターを活用した臼型滑り面と,エポキシ樹脂製コンクリート補修材を使用すること

  • 材料劣化の空間変動の確率・統計的表現とその既存構造物の性能照査への応用

    Project Year :

    2016.04
    -
    2020.03
     

     View Summary

    既存鉄筋コンクリート(RC)構造物では,コンクリートの品質,あるいはかぶり不足などが原因となり,中性化や塩害による鉄筋腐食が生じている場合がある.このような鉄筋腐食が生じたRC構造物の曲げ耐力やせん断耐力,あるいは靭性能評価を行う際には,構造物の各位置で空間的に変動する鉄筋腐食の影響を考慮する必要がある.X線装置を用いて鉄筋腐食の成長過程を連続的に撮影した昨年の研究成果を見る限り,鉄筋腐食の空間変動性はランダムな現象ながらも,確率場のパラメータを適切に定めることにより,確率統計的に再現可能である.つまり,例えば,平均質量減少率が10%のRC部材の曲げ耐力を予測する場合,部材内に生じ得る鉄筋腐食分布は,ある規則に従っており,その規則を満足する平均質量減少率10%の鉄筋腐食分布を多数作成することにより,このRC部材が発現し得る曲げ耐力分布(確率密度分布)を算定できると期待される.一方,現状では,鉄筋腐食の空間変動

  • 材料劣化の空間変動の確率・統計的表現とその既存構造物の性能照査への応用

    日本学術振興会  科学研究費補助金

    Project Year :

    2016.04
    -
    2020.03
     

  • Improvement of seismic response of bridges focused on uncertainty / discontinuity in structural system

    Project Year :

    2014.04
    -
    2018.03
     

     View Summary

    Due to 2011 Great East Japan Earthquake and 2016 Kumamoto Earthquake, many bridges suffered serious damages at structural boundaries and connections. In order to evaluate seismic response of bridges focused on discontinuity in structural system, shake table tests of seismic isolators in 2D were conducted to make rational numerical model, and improvement of design of collapse prevention device in bridge was proposed. And in order to evaluate seismic response of bridge focused on uncertainty, dynamic response of multi-degree-of-freedom systems was evaluated by changing the predominant frequency component of narrow band input for seismic action with high uncertainty by random vibration theory. Furthermore, new techniques were proposed to improve the post-peak behavior of reinforced concrete structure

  • Life-cycle management of bridges under seismic and airborne chloride hazards

    Project Year :

    2012.04
    -
    2016.03
     

     View Summary

    The evaluation of the displacement ductility capacity based on the buckling model of longitudinal rebars in corroded RC bridge piers is established, and a novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life-cycle seismic reliability assessment of these piers is proposed. Whereas the seismic demand depends on the results of seismic hazard assessment, the deterioration of seismic capacity depends on the hazard associated with airborne chlorides. In an illustrative example, a RC bridge pier was modeled as single degree of freedom. The longitudinal rebars buckling of this pier was considered as the sole limit state when estimating its failure probability. The findings show that the life-cycle reliability of RC bridge piers depends on both the seismic and airborne chloride hazards, and that the cumulative-time failure probabilities of RC bridge piers located in seismic zones can be affected by the effect of airborne chlorides

  • Three Dimensional Visualization of Steel Corrosion Process in RC Member Using X-Ray and Digital Image Processing

    Project Year :

    2013.04
    -
    2015.03
     

     View Summary

    It is important to estimate the amount of corrosion products in existing RC structures subjected to chloride attack. However, the corrosion process of rebar has not been investigated because of difficulties with observing it. Recently, X-ray technology has been applied to the visualization of concrete cracking to investigate the behavior of fracture process zone in concrete. In this study, digital picture processing method to estimate the amount of corrosion products in RC members is provided for X-ray photography. Then, based on the observation of deteriorated RC member using X-ray photography, corrosion process of rebar is visualized, and the effects of the amount of corrosion products on the corrosion cracking width and flexural strength of RC beam are examined

  • 社会基盤施設のライフタイム評価

    その他の研究制度

    Project Year :

    1999
    -
     
     

  • 構造物の信頼性設計法(耐震信頼性設計,耐久信頼性設計)

    地震防災フロンティア研究

    Project Year :

    1997
    -
     
     

  • seismic desigh for reinforced concrete structures

    Earthquake Disaster Mitigation Research Program

    Project Year :

    1997
    -
     
     

  • Mecharical properties of structural member with Ultra high strength materials

    Earthquake Disaster Mitigation Research Program

    Project Year :

    1997
    -
     
     

  • コンクリート構造の耐震設計

    地震防災フロンティア研究

    Project Year :

    1997
    -
     
     

  • reliability-based design of reinforced concrete structures and reliability-based optimization

    Earthquake Disaster Mitigation Research Program

    Project Year :

    1997
    -
     
     

  • Development of High Performance Seismic Members

    Project Year :

    1997
    -
     
     

     View Summary

    In this study, the development and the seismic design approach of high performance structures using RC and SRC members have been done. The results of the study from 2002 to 2004 are shown below.1. Shear strength characteristic of RC beams using high-strength materialsThe shear loading tests of RC beams without stirrup using high-strength concrete of compressive strength ranging to 130MPa have been carried out.(1)A shear strength equation of RC beams without stirrup using high-strength concrete has been suggested.(2)A shear strength equation of RC beams with stirrup using high-strength concrete and reinforcing bars has been suggested by referring to the previous test results.2. Uniaxial compressive strength characteristic of RC columns using high-strength materialsThe uniaxial compressive loading tests of RC columns (rectangular and circular section) have been carried out.(1)By measuring the strain distribution of the core concrete, it is possible to quantitatively evaluate the changing of failure region caused by the concrete strength and the quantity of tie reinforcement.(2)By using the compressive failure energy, the stress-strain relationship of confined concrete of normal to hi

  • マルチハザードを受ける道路ネットワークのライフサイクルレジリエンスと対策優先度(国際共同研究強化)

  • DEVELOPMENT OF REINFORCEMENTS WITH HIGH-STRENGTH AND HIGH-DUCTILITY AND ITS APPLICATION TO STRUCTURAL MEMBER

     View Summary

    The following are the principal achievements of the study.1.The mix proportions for super high strength concrete with compressive strength of 1,000kgf/cm^2 or more were established and the compressive strength, tensile strength, Young's modulus and other mechanical properties of the materials were investigated in detail.2.Steel reinforcement with a yield strength of about 7,000kgf/cm^2 and strain at tension failure time of 15% was developed.3.Bending loading testing of a reinforced concrete beam made of super high strength concrete and super high strength steel reinforcement was performed to study the mechanical properties of the beam under bending.4.Using concrete with compressive strength of 1,200kgf/cm^2 and steel reinforcement with yield strength of 7,000kgf/cm^2 as its tension reinforcement, the shear properties, particularly the shear dynamic strength, load-displacement relationship, and the state of the occurrence of strain and cracks of an RC beam without double reinforcement were experimentally studied. An experimental study of the shear properties of this kind of RC beam with double reinforcement was also done.5.Results of similar tests performed in the past were summariz

  • 橋脚の保有耐力を考慮した杭基礎の設計水平震度算定に関する確率論的考察

     View Summary

    本研究では,システムの破壊確率を精度良く算定できる構造系信頼性評価法とSQP法に基づく構造最適化手法を組み合わせた構造系の信頼性設計手法を援用することにより,場所打ち杭の設計水平震度の設定例を提示した.場所打ち杭の設計水平震度は,RC橋脚の保有水平耐力に相当する震度k_<hp>と部分係数γ_0の積と定義し,耐力階層化の考えに基づき,橋梁システムが持つ全ての限界状態から計算される安全性指標を橋脚に関わる限界状態のみから計算される安全性指標で代表させるための部分係数γ_0の設定を試みた.本研究により得られた主な研究実績を以下に示す.(1)Sorensenらが用いた確率論に基づく部分係数算定のための目的関数に,構造系信頼性評価法を適用することで,耐力階層化を図るための部分係数を算定することができた.(2)地盤モデル毎に算定される部分係数γ_0は,地震時に生じる地表面の最大応答変位と概ね相関関係を有している.また,各確率変数のばらつきを考慮し,かつ地盤変形の

  • Seismic Design Methodology Based on Reliability Theory in Consideration of Lifetime

     View Summary

    1. New evaluation method of lifetime risk in RC member is proposed on the basis probability matrix. It is clarified that current seismic method does not necessarily provide sufficient safety during the lifetime of RC structure.2. A new evaluation method for the probability of failure of a structural system based on reliability theory is proposed. From the numerical examples, it is demonstrated that this method possesses high accuracy and simplicity.3. Design flow charts which can cope with an arbitrarily given safety level are formulated by reliability-based optimal theory considering structural system. Then the proposed method is applied to the seismic design of rigid-frame bridge piers and RC bridge pier. As a result, it is confirmed that (1) the RC bridge piers so as to attain the prescribed reliability can be designed by the proposal method and (2) the safety of bridge piers, which are deigned based on the current code, are not uniform.4. The effect of uncertainties in reinforced concrete (RC) bridge systems on the response of the RC bridge pier and cast in place pile were statistically and analytically studied, and quantitative evaluations of variations in that response were o

  • 蒸気養生不要の高強度コンクリートの開発および強度発現・耐久性メカニズムの解明

     View Summary

    国内の全重油使用料の約0.6%を使用する蒸気養生を必要としない製品用コンクリートが開発されれば、地球環境問題への貢献は大きい。また、生コンクリートとして使用可能であれば建設期間の短縮等によりコストの大幅な縮減につながると期待される。当研究グループでは、このニーズに応えるべく、この種の超早強性コンクリートの開発を試み、ある種の混和材料を使用することで超早強性を有するコンクリートを開発した。さらに、開発されたコンクリートに対する性能試験の結果、耐久性等に関しては従来の蒸気養生されたコンクリートと同等の性能を有することを実験的に確認した。最後に、この混和材の使用によりもたらされる超早強性の強度発現および耐久性のメカニズムの解明および各種配合条件とこれらの関係を化学的あるいは微視構造的に把握した。得られた実験成果を以下に記す.(1)蒸気養生不要の超早強性コンクリートについて、配合条件と各種物性値(圧縮強度、引

  • ISO2394に対応したRC橋脚の耐震設計に用いる部分安全係数評価

     View Summary

    (1)研究代表者が先に提案してきた構造系信頼性設計手法を援用することで,構造系の信頼性を考慮した信頼性解析を行うことなく,設計対象構造系の破壊確率が要求信頼性レベル(目標破壊確率)を満足できる設計を可能にする安全係数の算定手法を体系化した.(2)橋脚の固有周期と降伏耐力比Ru(弾性応答水平力P_Hと橋脚の降伏耐力Pyの比(Ru=P_H/Py))より,エネルギー一定則から弾塑性応答変位を推定する際に含まれる安全マージンやばらつきを定量化し,信頼性解析で必要となる確率変数のパラメータの設定を行った.(3)断面形状やせん断スパン比などが異なる46基のRC橋脚を検討対象橋脚群として,提案手法により,その耐震設計に用いる基本安全係数を試算した.その結果,地震時保有水平耐力法により耐震設計されたRC橋脚の安全性指標βsysは,βsys=0.9〜2.4の範囲でばらついているのに対し,試算した基本安全係数と定義した設計規準式を用いることにより,確率・統計の計算を一切必要とすることなく,目標

  • レベル2地震動を受ける橋梁システムを対象とした信頼性理論に基づく限界状態設計法

     View Summary

    構造物の信頼性に関する一般原則(ISO2394)に基づく設計規準の整合化が国際的に検討されており,今後,コンクリート構造物を対象とする設計規準においても,これに準拠する確率論的な概念を導入した限界状態設計法への移行が検討されると考える。こうした背景のもと,RC構造物を対象とした耐震信頼性設計法に関する研究を進めており,ある地震動作用下の条件付破壊確率と目標破壊確率の差を最小化する最適化問題を解くことにより,構造系の信頼性を考慮した信頼性解析を行うことなく,目標破壊確率を概ね確保した設計を可能にする安全係数の算定手法を体系化している。ただし,この手法では,建設地毎の地震ハザードの相違を考慮できないため,提示する安全係数は,ある特定の地震動作用に対する構造物の破壊確率を目標値に漸近させているに過ぎない。超低頻度な領域で,地震動を確率的地震ハザード曲線に基づき評価することには,種々の問題が指摘されているが,設計規準の国際整合化

  • 地震動評価に係る圧倒的不確定性存在下における耐震部材の開発とその性能開示

     View Summary

    開発した超高強度RC柱部材の年損傷確率を以下の手順で算定し,普通強度RC柱部材のそれと比較した.1.建設地点の選定と設計条件の設定:建設地点は,日本全国から任意に10箇所を選定した.対象構造は,上部構造は連続鋼鈑桁橋を想定し,地盤はI種地盤上に位置すると仮定した.そして,普通強度構成材料を用いて単柱式RC橋脚を耐震設計する.耐震設計する際は,現行の道路橋示方書の基準を満足するようにした.その上で,同じ断面諸元,鉄筋量のもとで,コンクリート圧縮強度を120N/mm^2,軸方向鉄筋降伏度を785N/mm^2,横拘束筋降伏強度を1400N/mm^2としたRC橋脚を耐震設計した.2.確率的地震ハザード曲線の作成:地震ハザード評価コードSHEATを用いた.3.時刻歴波形の合成とフラジリティカーブの作成:着目する地震動強さに対応した地震波(加速度時刻歴波形)を作成した.ここでは,振幅と位相のばらつきを考慮した地震波を合成した.任意の地震動強さの作用に対するRC橋脚の条件付損傷確率(終局変位を超過する確率)

  • Development of High-Strength Pile Foundation and Reliability Seismic Design Considering Liquefied Ground

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    In this study, high-strength concrete pile is investigated not to be damaged by large earthquakes even if it is embedded in liquefied ground. As the experimental results of static loading tests of proposed pile specimens and centrifuge tests of the pile embedded in soil, high seismic performance of the proposed high-strength concrete pile is indicated. Moreover, seismic design of the proposed high-strength concrete pile considering soil effect is proposed

  • Updating of random variables associated with demand and capacity using observation information and estimates of remaining lifetime of deteriorated structures

     View Summary

    This study presents a framework for estimating the remaining lifetime of reinforced concrete structures in a marine environment based on the observation information such as visual inspection of corrosion cracks and chloride concentration distributions. Random variables used in the prediction of corrosion process of concrete component could be updated by Sequential Monte Carlo Simulation. In addition, growth process of steel corrosion was visualized by X-ray photography in order to understand the spatial distribution of corroded steel used in the proposed framework

  • Establishment of system of science and technology on evaluation of performance of concrete structures with material deterioration

     View Summary

    Structural performance of reinforced and prestressed concrete structures which had been deteriorated by reinforcement corrosion, alkali-silica reaction and frost damage were investigated through laboratory test, loading test of actual structures and nonlinear finite analysis. Number of experimental facts and mechanisms about influences of material deterioration in structures on the structural performance were found in this study. Evaluation method of residual structural performance of deteriorated existing structures based on on-site investigation and numerical simulation was proposed

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Presentations

  • Risk and resilience of civil infrastructure systems under extreme events

    AKIYAMA, Mitsuyoshi  [Invited]

    IABSE Symposium 2019 

    Presentation date: 2019.03

  • Life-cycle reliability of bridges under independent and interacting hazards

    Mitsuyoshi Akiyama  [Invited]

    9th International Conference on Bridge Maintenance, Safety and Management (IABMAS2018)  (Melbourne, Australia) 

    Presentation date: 2018

  • Lessons from recent major earthquakes in Japan: Emphasis on reliability assessment of structures under multiple hazards

    Mitsuyoshi Akiyama  [Invited]

    18th ASEP International Convention  (Quezon, Philippine) 

    Presentation date: 2017

  • Reliability-based assessment of structures for extreme events

    Mitsuyoshi Akiyama  [Invited]

    IABSE Summit 2016  (Helsinki, Finland) 

    Presentation date: 2016

  • Probabilistic approach for road network retrofitting prioritization under seismic and tsunami hazards

    Mitsuyohis Akiyama  [Invited]

    5th International Symposium on Reliability Engineering and Risk Management (ISRERM2016)  (Seoul, Korea) 

    Presentation date: 2016

  • Lessons from the recent earthquakes in Japan based on field investigations of damage to bridge

    Mitsuyoshi Akiyama  [Invited]

    MPSS (Ministry of Public Safety and Security) Meeting  (Seoul, Korea) 

    Presentation date: 2016

  • Long term performance of concrete bridges under multiple hazards

    Mitsuyoshi Akiyama  [Invited]

    TU1406 COST Action Workshop  (Delft, the Netherlands) 

    Presentation date: 2016

  • Long term performance of concrete bridges under extreme events.

    Mitsuyoshi Akiyama  [Invited]

    9th Austroads Bridge Conference, Sydney  (Sydney, New South Wales, Autralia) 

    Presentation date: 2014

  • Life-cycle design of bridges under multiple hazards: Earthquake, tsunami and continuous deterioration

    Mitsuyoshi Akiyama  [Invited]

    11th ICOSSAR (International Conference of Structural Safety and Reliability)  (New York, USA) 

    Presentation date: 2013

  • Life-cycle reliability of concrete bridges under both extreme events and hazard associated with continuous deterioration

    Mitsuyoshi Akiyama  [Invited]

    IStructE Conference on Structural Engineering in Hazard Mitigation  (Shanghai, China) 

    Presentation date: 2013

  • Lessons from the 2011 Great East Japan Earthquake: Emphasis on life-cycle structural performance

    Mitsuyoshi Akiyama  [Invited]

    3rd International Symposium on Life-Cycle Civil Engineering  (Vienna, Austria) 

    Presentation date: 2012

  • On life-cycle reliability under earthquake excitations of corroded reinforced concrete structures

    Mitsuyoshi Akiyama  [Invited]

    2nd International Symposium on Life-Cycle Civil Engineering  (Taipei, Taiwan) 

    Presentation date: 2010

  • Concentric Loading Test of RC Columns with Normal- and High-Strength Materials and Averaged Stress-Strain Model for Confined Concrete Considering Compressive Fracture Energy

    The 2nd fib congress 

    Presentation date: 2006

  • Concentric Loading Test of RC Columns with Normal- and High-Strength Materials and Averaged Stress-Strain Model for Confined Concrete Considering Compressive Fracture Energy

    The 2nd fib congress 

    Presentation date: 2006

  • Application of Reliability Theory to the Durability-Design of Concrete Structures Subjected to Corrosion

    The 2nd fib congress 

    Presentation date: 2006

  • Application of Reliability Theory to the Durability-Design of Concrete Structures Subjected to Corrosion

    The 2nd fib congress 

    Presentation date: 2006

  • Report of Research Project on Structural Performance of Deteriorated Concrete Structures by JSCE 331 - Reliability Approach

    Life Cycle Management of Coastal Concrete Structures 

    Presentation date: 2006

  • Report of Research Project on Structural Performance of Deteriorated Concrete Structures by JSCE 331 - Reliability Approach

    Life Cycle Management of Coastal Concrete Structures 

    Presentation date: 2006

  • STRESS-STRAIN MODEL OF HIGH-STRENGTH CONCRETE CONFINED BY RECTANGULAR TIES

    World Conference of Earthquake Engineering 

    Presentation date: 2004

  • STRESS-STRAIN MODEL OF HIGH-STRENGTH CONCRETE CONFINED BY RECTANGULAR TIES

    World Conference of Earthquake Engineering 

    Presentation date: 2004

  • UNCERTAINTIES AFFECTING THE SEISMIC RELIABILITY OF RC BRIDGE PIERS

    World Conference of Earthquake Engineering 

    Presentation date: 2004

  • UNCERTAINTIES AFFECTING THE SEISMIC RELIABILITY OF RC BRIDGE PIERS

    World Conference of Earthquake Engineering 

    Presentation date: 2004

  • Evaluation of Seismic Performance of RC Bridge Piers Based on Reliability Theory in Consideration of Structural System

    Concrete Structures in Seismic Regions 

    Presentation date: 2003

  • Evaluation of Seismic Performance of RC Bridge Piers Based on Reliability Theory in Consideration of Structural System

    Concrete Structures in Seismic Regions 

    Presentation date: 2003

  • Ductility Design of Concrete Encased Steel Piers

    The first fib congress 

    Presentation date: 2002

  • Seismic Safety Evaluation of Prestressed Concrete Tank in Consideration of Level II Earthquake Motions

    The first fib congress 

    Presentation date: 2002

  • Proposal of the Partial Safety Factors for Seismic Design of Concrete Structures in Consideration of Reliability Theory and Optimization of Structural Systems

    The first fib congress 

    Presentation date: 2002

  • Proposal of the Partial Safety Factors for Seismic Design of Concrete Structures in Consideration of Reliability Theory and Optimization of Structural Systems

    The first fib congress 

    Presentation date: 2002

  • Seismic Safety Evaluation of Prestressed Concrete Tank in Consideration of Level II Earthquake Motions

    The first fib congress 

    Presentation date: 2002

  • Ductility Design of Concrete Encased Steel Piers

    The first fib congress 

    Presentation date: 2002

  • SAFETY EVALUATION METHOD FOR STRUCTURAL SYSTEMS AND ITS APPLICATION TO SEISMIC DESIGN OF THE RC BRIDGE PIER

    World Conference of Earthquake Engineering 

    Presentation date: 2000

  • SAFETY EVALUATION METHOD FOR STRUCTURAL SYSTEMS AND ITS APPLICATION TO SEISMIC DESIGN OF THE RC BRIDGE PIER

    World Conference of Earthquake Engineering 

    Presentation date: 2000

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Specific Research

  • 機械学習と確率論的アプローチによる腐食ひび割れのあるRC部材の残存耐荷力推定法

    2021  

     View Summary

    RC構造物では,塩害などの外的作用により鉄筋腐食が発生し,その後,腐食生成物の膨張圧により腐食ひび割れが表れる.腐食ひび割れを有するRC構造物は,耐荷力の深刻な低下が懸念され,現有性能を精緻に評価する必要がある.一方,腐食ひび割れ幅と鉄筋腐食量の関係には大きなばらつきが存在し,腐食ひび割れ幅から実験式に基づいて予測される鉄筋腐食量の精度は極めて低い.本研究では,LSTMと既往の実験結果,さらには有限要素解析を用いることで,腐食ひび割れ幅からRC部材内部で生じ得る鉄筋腐食分布群の作成を可能にした.ケーススタディとして,腐食ひび割れ幅の情報からMonte Carlo法により対象RCはりの残存耐荷力の確率密度分布を試算した.

  • 摩擦振子型免震機構付き橋脚に用いる滑り面形状の最適化と寸法効果に関する実験的研究

    2020  

     View Summary

     ダメージフリー橋梁の開発を目指し,摩擦振子型免震機構を有するRC橋脚を提案するとともに,その震動実験を行ってきた.提案構造は,橋脚中間部に滑り面を設けることで橋脚下部に伝達される地震時慣性力を大幅に低減することができる.特徴は3Dプリンターで製作したコンクリート型枠を用いることで,複雑な形状を有する滑り面を安価に製作できる点にある.本研究では,過去に用いた橋梁模型を大型化し,提案構造の地震応答に及ぼす寸法効果の影響を検討するための震動実験を実施し,提案構造で生じる応答加速度の低減効果や残留変位の大きさが供試体寸法に依存しないことを確認した.

  • 鉄筋腐食の空間変動性を考慮したRC部材の構造性能評価

    2019  

     View Summary

     鉄筋コンクリート(RC)部材に生じる鉄筋腐食などの材料劣化は,場所ごとに腐食程度が大きく異なり,空間的に変動している.劣化RC部材の3D-X線撮影により得られる鉄筋腐食分布からその空間変動を確率・統計的に表現するためのパラメータを同定するとともに,鉄筋腐食の不均一な分布がRC部材の耐力や変形能に及ぼす影響を実験的・解析的に検討した.また,既存RC構造物から得られる数点の点検・検査結果からデータ同化手法を用いることで,RC構造物内に生じている鉄筋腐食量の空間的な変動を同定し,数値解析によりその耐力や変形能を算定した.これと残存供用期間に応じて求められる作用荷重との比較を行うことで,既存構造物の合理的な性能照査やライフサイクル解析が可能となった.

  • 2次元非ガウス確率場の拡張と点検・検査結果への同化による鉄筋腐食分布の推定

    2018  

     View Summary

    本研究では,まず,RC部材の電食実験と,そのX線撮影・ディジタル画像処理により,RC構造物内の鉄筋腐食分布がどのように進展・成長するのかを理解した.X線撮影には,比較的規模の大きいRC部材をそのまま収容できる装置(早稲田大学所有)を使用した. 次に,鉄筋腐食分布の連続的な変化を2次元非ガウス確率場にてモデル化した.Lehigh大学のProf. Bocchiniの研究グループにおいて開発が進められている行列型非ガウス確率場を応用した.本モデルは,離散的に配置された鉄筋の腐食分布の表現に適しており,計算式で必要となるパラメータを前述の実験結果に基づき決定した.最後に,既存RC構造物から得られる数点の鉄筋腐食量に応じて,鉄筋腐食分布の絞込みを行った.鉄筋腐食量の測定位置とその鉄筋腐食量の測定結果を与え,更新理論を介することにより,点検・検査結果に応じた鉄筋腐食量の分布を同定した.数点の鉄筋腐食量の点検・検査結果から,大規模なRC構造物全体に拡がっている鉄筋腐食分布を出力できるようにしたのが本研究の成果である.

  • 南海トラフ地震による強震動と津波の影響を受けるインフラ構造物のリスク評価

    2018  

     View Summary

    単一の地震ハザードに対する信頼性の確保から,それを起因として引き起こされる,異なるマルチハザードを想定し,構造物の信頼性に影響する支配的なハザードの抽出などを行う必要がある.本研究では,マルチハザードを受ける構造物の信頼性評価に関する基礎研究として,南海トラフ地震により引き起こされる強震動および津波を想定した.信頼性のアプローチを南海トラフ地震の影響地域にある構造物に適用することで,その破壊可能性を支配するハザードの抽出や異種構造物(橋梁・盛土)の安全性の大小などを比較した.これらの情報は,対策を優先的に施していく地域や構造物の同定に活用される.

  • 構造形態の工夫によるRC柱のダメージフリー化と震動実験による性能確認

    2017  

     View Summary

    本研究では,これまでの既存研究の知見を基に二方向入力を受ける場合を想定して摩擦振子型免震機構付き柱を設計し,震動実験によりその地震時挙動を確認した.一方向入力の場合と異なり,滑り曲面上を斜め方向に摩擦振子が滑る場合の滑り性能の確保,あるいはそれに適した滑り曲面形状や橋脚の配置方法などが問題となった.また,骨組解析モデルを用いた非線形動的解析も行い,提案構造の地震時挙動を数値解析的に評価するための基礎検討も行った.なお,これまでに観測されている範囲の鉛直地震動の大きさでは,本構造の地震時挙動に鉛直地震動が及ぼす影響は極めて限定的であることから,本実験では,鉛直方向成分の入力は行わなかった.

  • 南海トラフ地震による三重県沿岸部に架かる橋梁構造物の地震・津波リスク評価

    2016  

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     断層パラメータ,強震動の距離減衰や津波伝播,あるいは構造物の応答評価や耐力算定などに介在する種々の不確定性を統合し,強震動,あるいは津波により構造物が損傷する確率を算定する一連の手順を示した.各パラメータの継続的な見直しは,当然,必要であるが,この一連の手順により,各パラメータの変動が着目する構造物の安全性に及ぼす影響を定量的に把握することが可能となる.限られた予算の中では,全てのハザードに対して最悪のシナリオを想定し,対策を施していくことは困難である.起こり得るシナリオと,その評価に伴う不確定性を反映し,着目する構造物の安全性に最も影響する支配的なハザードを抽出,あるいは最も安全性の低い構造物を同定する上で,提示した信頼性のアプローチは有用である.

  • 木構造状画像フィルタによる3次元鋼繊維分布の抽出とSFRC部材の構造性能評価

    2016  

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    (1) 鋼繊維補強コンクリート(SFRC)が有する繊維の配向性と分散性の問題に対し,X線撮影により鋼繊維を可視化し,それから曲げ引張への抵抗の大小を表現するパラメータ(RNF)を定義した.(2) RNFと,SFRCの引張軟化曲線の骨格曲線を規定するパラメータを関係付けることにより,X線画像からSFRCの引張軟化曲線を求められるようにした.(3) SFRCはりのX線画像を用いたFEM解析を実施し,実験結果と比較した.X線画像により鋼繊維が可視化され,各要素の引張軟化曲線をその情報に基づき定めることで,X線画像がない場合に比べて,実験と解析結果の差を小さくできることを確認した.

  • 鋼繊維分布の3D-X線撮影結果を用いたSFRC部材の力学特性評価

    2015  

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    鋼繊維補強コンクリート(SFRC)は,鋼繊維の配向性と分散性の問題のため,同条件で製作した供試体であっても,その力学特性は供試体毎に大きく異なる.X線技術とディジタル画像処理を応用することで,コンクリート内に広がる鋼繊維を一本一本可視化し,それを数値解析の入力情報として取り込むことで,SFRC部材の力学特性の評価精度を大幅に改善できると期待される.この着眼のもと,本研究では主に次の成果を得た.(1) SFRC部材内の鋼繊維分布を可視化するX線撮影と画像処理技術の確立(2) 鋼繊維分布のX線撮影結果を反映した数値解析用インプット情報の作成(3) SFRC部材の構造実験結果とX線撮影・数値解析による計算値の比較に基づく精度検証

  • RC部材内に生じる鉄筋腐食成長過程の3次元可視化とその維持管理の高度化への利用

    2015  

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     本研究は,X線によりコンクリート内の鉄筋腐食の状態を撮影し,鉄筋の非腐食域の境界を捉えるためのディジタル画像処理方法などを検討した.具体的には,腐食量と腐食の分布が既知の鉄筋をコンクリート中に埋め込み,その状態をX線撮影し,ディジタル画像処理方法の違いがX線撮影画像から予測される鉄筋腐食量の精度に及ぼす影響などを検証した.次いで,電食にて劣化させたRCはり部材のX線撮影を行い,鉄筋質量減少率の不均一さの程度や形成過程を観察した.また,鉄筋質量減少率とコンクリート表面に表れる腐食ひび割れ幅の関係,さらには,部材内部の鉄筋質量減少率の空間的な変動と曲げ耐力の関係などに関する基礎資料を得た.

  • 材料劣化が生じたインフラ構造物の構造性能評価と維持管理に関する研究

    2014  

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    Reinforcedconcrete (RC) structures in a marine environment deteriorate with timedue tochloride-induced corrosion of reinforcing bars. This paper presentsreliability-based durability assessment of existing RC structure in a marine environment.A simple assessment criterion with partial factors that satisfy the targetreliability level within the remaining life-time of existing RC structure ispresented. A procedure to obtain the partial factors updated by the SequentialMonte Carlo Simulation is indicated. In this procedure, the chlorideconcentration distribution by coring test is used as observational data.Partial factors could be determined by taking into consideration the reductionof uncertainties associated with the prediction of chloride-induced corrosion.Partial factors for durability assessment of existing RC structures could bereduced compared with thosefor durability design of new RC structures.

  • 構造形態の工夫による超免震橋梁の開発

    2013  

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     兵庫県南部地震以降,耐震解析手法には長足の進歩が見られるのに対して,地震動評価には依然として圧倒的な不確定性が存在する。このような不確定性に対峙し,構造物の地震時安全性を確保するためには,地震動の不確定性の影響を受けないほど構造物の性能を高める必要がある。コンクリート系の耐震部材の開発では,この手段として部材靭性率を大きくしてきた。既に,降伏変位の約20倍までの応答変位が生じても,安定した曲げ挙動を呈するRC柱も開発されている。しかし,部材変形能により地震エネルギーの吸収を期待した構造は,基本的に地震後にある程度の修復作業を必要とする。橋梁は,地震後の救助・救急活動や,都市の復興に重要な役割を果たすことを考えると,地震中の安全性と地震後の供用性をともに確保できる技術開発が必要である。この背景のもと,摩擦振子型免震機構を有するコンクリート橋脚を提案し,その震動台実験により,基本的な地震時の応答特性を確認した。摩擦振子が滑り曲面上を運動することで,上部工に作用する慣性力の下部構造への伝達が遮断され,滑り曲面の形状および摩擦振子と滑り曲面間の摩擦で決定されるせん断力に起因する断面力が橋脚基部や基礎に作用する。これにより,地震動の大きさに関係なく,橋脚基部や基礎に作用する最大断面力を構造諸元のみで決定できるため,橋脚や基礎の弾性設計が可能となる。さらに,免震支承等の特別な装置を必要とせず,構造形態のみの工夫により長周期構造を実現するため,免震化に伴うコスト増を抑えることができる。過去に実施した震動台実験により,地震中の橋梁の安全性を確保する上で,摩擦振子型免震機構を有するコンクリート橋脚の有用性を確認できた。ただし,地震後の供用性を本構造が確保できていることを示すには,摩擦振子と滑り曲面間で生じる地震後の相対変位(残留変位)についての検証が必要である。 一般的な単柱式橋脚で生じる残留変位に関する既往の研究には,例えば,川島らの残留変位比応答スペクトルに関する検討がある。残留変位は,1自由度系に置換した橋脚の骨格曲線をバイリニアで表現したとき,その初期剛性と2次勾配の比に大きく依存し,さらに地震動毎に得られる残留変位のバラツキは非常に大きいことが示されている。一方で,橋脚に生じる残留変位の発生要因を橋脚の損傷のみに起因するものとして捉え,橋脚下端部と上部工の慣性力作用位置の相対変位で橋全体系の残留変位の大きさを表現すること,および震動台実験や被災橋脚から実測された残留傾斜角との比較から,RC橋脚の残留変位の計算には相当に大きなモデル誤差が含まれることが指摘されている。 上記の背景のもと,本研究では,摩擦振子型免震機構を有するコンクリート橋脚の震動台実験を実施し,滑り曲面の形状,あるいは地震動特性などが残留変位やそのバラツキの大きさに与える影響を確認した。また,今回の検討に用いた地震動は,現行の耐震設計で規定されるレベル2地震動よりもさらに大きく,それによる最大滑り変位が生じた後にも,本構造に生じる残留変位は小さい値に抑えられることを確認した。今後の継続した実験的検討が必要なものの,本構造は,地震中の安全性と地震後の供用性を兼ね備えたダメージフリー橋梁の一つになり得るものである。一方で,実験的に得られる残留変位の大きさを解析により定量評価することは困難であった。残留変位を解析的に得るための数値モデルの高精度化が必要である。

  • 津波ハザードを受ける社会基盤構造物のリスク評価とその軽減策

    2012  

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     2011年3月11日に発生した東北地方太平洋沖地震により,東日本沿岸部にある社会基盤構造物(道路や鉄道ネットワーク)は壊滅的な被害を受けた.道路や鉄道には,地震後の避難や救助救急等の緊急活動,あるいは,ライフラインの復旧活動を支える交通基盤として重要な役割が期待されていたが,その機能を十分に果たすことができなかった.その原因となったのは,過去に発生した社会基盤構造物の地震被害で観察されなかった2つの新しい破壊形態が見られたことによる.(1) 津波による構造物の流出・倒壊(2) 塩害劣化により耐震性能低下が生じた構造物の強震動による損傷 近い将来に必ず発生する東海・東南海・南海地震でも,この(1)と(2)により太平洋沿岸部にある社会基盤構造物は相当の被害を受ける可能性がある.本研究では,(1)と(2)の損傷メカニズムを実験的・解析的アプローチにより解明するとともに,東海・東南海・南海地震に対する被害シミュレーション(リスク評価)と,その被害を軽減する方策を提言した.具体的な成果を以下に示す. ⇒国内外の社会基盤構造物の耐震設計基準で津波作用を考慮したものは存在しない.本研究では,数値シミュレーションにより,津波・構造物の連成解析を行い,それらに基づき橋梁の対津波落橋防止構造の設計法を構築した. ⇒東海・東南海・南海地震の影響を受ける海岸線近くの橋梁は膨大な数にのぼる.これら橋梁群の津波リスクを評価した.対津波落橋防止構造を既存橋梁に導入する投資と,それにより低減される津波リスクの比較を行い,この投資の価値を定量的に議論できるフレームワークを提示した. ⇒海岸線近くにある橋梁は,津波以外にも脅威となる自然作用が存在する.強震動と海洋からの飛来塩分である.東海・東南海・南海地震の影響を受ける地域にある社会基盤構造物は,建設後,既に50年近くになる構造物が多数あり,材料劣化が顕在化している.このような材料劣化が生じた構造物が強震動を受けた場合には,脆性的な破壊が生じる可能性が指摘されるものの,材料劣化が生じた構造物の安全性を評価する過程には未解決な問題が多数残されている.本研究は,材料劣化が生じた構造物の実験および解析を行い,この種の構造の耐震安全性評価法を提示した. これら一連の成果として,地震・津波・塩害のマルチハザードを受ける社会基盤構造物のリスク評価法を提示している.

  • 摩擦振子型免震機構付き橋脚を有するダメージフリー橋梁の開発

    2012  

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     兵庫県南部地震以降,耐震解析手法には長足の進歩が見られるのに対して,地震動評価には依然として圧倒的な不確定性が存在する。このような不確定性に対峙し,構造物の地震時安全性を確保するためには,地震動の不確定性の影響を受けないほど構造物の性能を高める必要がある。これまでのコンクリート系の橋梁耐震部材の開発では,この手段として部材靭性率を大きくしてきた。例えば,インターロッキング式帯鉄筋を有する鉄筋コンクリート(RC)橋脚,軸方向鉄筋や帯鉄筋の配筋方法,あるいはコアコンクリート内にスパイラル鉄筋を配筋するなどの工夫をしたRC橋脚,そして,鉄骨鉄筋コンクリート橋脚などの研究がある。しかし,このような部材変形能により地震エネルギーの吸収を期待した構造では,地震後に相当の残留変位が生じる可能性がある。橋梁は,地震後の救助・救急活動や,都市の復興に非常に重要な役割を果たすことを考えると,単に橋梁の地震中の安全性を確保するだけではなく,地震後の供用性までを考慮した部材開発が求められる。 この背景のもと,摩擦振子型免震機構を有するコンクリート柱を提案し,その振動台実験により,基本的な性能を確認した。橋脚を2つの部位に分割し,分割した位置に滑り曲面を設けている。上側にある部位(摩擦振子)が滑り曲面上を滑り,下側にある部位(滑り曲面を有する橋脚や基礎など)に作用する地震時慣性力を低減する。従来の曲げ破壊型のRC橋脚は,橋脚天端部に水平力が作用するとその下端部に大きな曲げが作用するのに対して,本構造は,滑りにより力の伝達を遮断し,さらに曲面の存在により地震後の残留変位を抑えることを期待している。 しかし,既発表の内容では,摩擦振子が半径一定の曲面(定曲面)上を滑るため,大きな地震力を受けると,桁の水平移動に伴いその上方への変位(アップリフト)や,橋脚下端に作用する地震時慣性力が大きくなり,橋脚の下端部や基礎などが損傷する可能性がある。これを避けるためには,半径の大きな曲面を用いることが考えられるが,その場合には,摩擦振子の原点回帰が期待できず,地震後に大きな残留変位が生じることが懸念される。 そこで,本研究では,摩擦振子が滑る曲面の形状を工夫することで,上記の問題の解決を試みた。具体的には,水平変位が小さいときには下に凸の小さな半径の曲面上を摩擦振子は滑り,さらに大きな地震力の作用を受けて水平変位が大きくなったときには,上に凸の曲面,あるいは直線上を滑るように曲面形状を変更した。この工夫をしたコンクリート柱を持つ橋梁模型を作製し,その振動台実験により地震応答特性を確認した。結果として,半径一定の滑り曲面を用いた場合に比べ,変動曲面上を摩擦振子が滑る場合には,コンクリート橋脚の下端部に作用する地震時慣性力を低減でき,一方で地震後の残留変位も大きくならないなど,その耐震性能を改善できることを示した。

  • 東北地方太平洋沖地震で損壊した橋梁の被害分析

    2011  

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     2011年東北地方太平洋沖地震により,岩手県・宮城県・福島県内にある多くの道路橋と鉄道橋が被災した.被災の原因は,地震動自体の動的作用によるもの,津波の作用によるもの,あるいは地震動により損傷し,その後の津波の作用により倒壊したもの,の3つに分類できる.本研究では,東北地方太平洋沖地震で被災した橋梁の被害分析を進め,復興時のインフラ整備にあたっての提言,あるいは近い将来に発生が予想される東海・東南海・南海地震への対策を提言することを目的とした. 平成23年春,夏,そして秋と,研究代表者は,土木学会地震工学委員会被災調査団メンバーなどの一員として,橋梁の被災状況を確認した.調査により明らかとなった課題は,以下の3つであった.(1)宮城県や岩手県沿岸部にある国道45号線に架かる道路橋,仙石線や気仙沼線などの鉄道橋(架道橋や架線橋)が津波により壊滅的な被害を受けていた.重さ数百トンもある橋梁上部工が数百メートルも流出している例も見られた.特に道路橋の流出は,現地の復興の大きな妨げとなった.(2)我が国で初めて,免震橋梁に大きな損傷が生じた.免震系の積層ゴム支承が完全に破断している事例もあった.現地の調査,およびその後に行った材料試験から,環境因子により材料的な劣化が生じ,それが地震被害を大きくした可能性が指摘された.(3)兵庫県南部地震以降,鉄道各社では耐震補強を積極的に進めてきた.落橋につながる脆性破壊となる柱を抽出し,優先的に耐震補強を行っている.しかし,今回の東北地方太平洋沖地震では,非常に多くの柱が損傷している.何故に耐震補強が見送られた部材で損傷が生じたのかを詳細に分析し,それに基づきこの種の部材に対する耐震補強策を講じる必要がある. 上記の3項目に対して,主に数値解析的な検討を重ねることで,以下の成果を得た.(i)津波の作用による橋梁の流出への対応法の提案:津波の作用に対する設計は全く行われていないが,我が国の橋梁は,フェールセーフ機能として,非常に頑丈な落橋防止装置を有している.この落橋防止構造の改良により,対津波用の落橋防止構造の設計要件を整理した.(ii)非常に長い地震動の継続時間とそれに伴う免震装置への過大な正負交番作用への対応法の提案:FEMをベースに免震支承部の非線形時刻歴動的解析を実施することで,継続時間やねじり,あるいは繰り返しの引張力が免震支承部の耐震性能に与える影響を検証した.また,ゴム支承の材料劣化と地震動の作用の複合による橋梁の安全性評価も実施した.(iii)部材破壊モード判定法の見直し:地盤の拘束や材料強度のバラツキ,さらには,曲げやせん断の耐力評価に伴うバラツキの影響により,曲げやせん断の破壊モードの判定には大きな不確定性が伴う.この種のバラツキの存在下でも確実に破壊モードの判定を実施できる手法を提案した.

  • 摩擦振子型免震機構を用いたダメージフリー橋梁の開発

    2011  

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     兵庫県南部地震以降,耐震解析手法には長足の進歩が見られるのに対して,地震動評価には依然として圧倒的な不確定性が存在する.このような不確定性に対峙し,構造物の地震時安全性を確保するためには,地震動の不確定性の影響を受けないほど構造物の性能を高める必要がある.これまでのコンクリート系の耐震部材の開発では,この手段として部材靭性率を大きくしてきた.鉄道橋では,既に,降伏変位の約20 倍までの応答変位が生じても,安定した曲げ挙動を呈するRC 系の柱も開発されている.しかし,このような部材変形能により地震エネルギーの吸収を期待した構造では,地震後に相当の塑性変形が残留する.橋梁は,地震後の救助・救急活動や,都市の復興に重要な役割を果たすことを考えると,単に構造物の安全性を確保するだけではなく,地震後の即座の使用性までを考慮した部材開発が必要である. 以上の背景のもと,本研究では,橋脚に摩擦振子型免震機構を適用し,曲面形状を適切に定めることにより,本来求められる性能を満たす橋梁(ダメージフリー橋梁)の提案を行った.提案するすべり面形状を含む複数の橋梁モデルを作製して1 方向振動台実験を行い,その性能を確認した. 本研究により得られた知見を以下に示す.1. 現行の耐震設計に使用する規定地震動に対しては無損傷,想定外地震動の作用時にも1 つの損傷モードしか起こらない橋梁をダメージフリー橋梁と定義し,円弧と直線のすべり面を有する曲面形状を用いた摩擦振子型免震機構を橋脚に適用した橋梁を提案した.2. 振動台実験により,提案する曲面形状が半径一定の円弧状の形状などの他の形状と比較して,優れた性能を有することを確認した.半径一定の円弧状の曲面形状では,曲率半径により固有周期を大きくすることで加速度の低減が図れるが,一方で変位は大きく発生し,これらはトレードオフの関係にあることが確認された.提案する曲面形状では,地震動強さが小さい場合には変位,地震動強さが大きい場合には加速度を低減させるといったように,地震動の強さに応じて性能を変化させられることを確認した.3. 最大加速度および最大変位は,簡単なバイリニアモデルで再現が可能である.しかし,残留変位については,摩擦係数を詳細に評価するモデルを用いたとしても再現が困難であることが確認された.そのため,摩擦振子型免震機構における可能最大残留変位を定義することで残留変位の最大発生値を評価する必要があることを示した.4. 曲面すべり面を有することによる鉛直変位の発生に対して,桁の損傷抑制の観点から満たすべき曲面形状について検討した.5. 提案する曲面形状を有するダメージフリー橋梁の設計フローを示し,実際に設計を行った.その結果,満たすべき性能を満足することを解析的に確認した.

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Committee Memberships

  • 2019
    -
    Now

    Managing Editor of Structure and Infrastructure Engineering

  • 2017
    -
    Now

    IABSE  Vice Chair of Commission 6 - Sustainability, IABSE

  • 2016
    -
    Now

    Editorial Board Member of Structural Safety

  • 2016
    -
    Now

    Associate Editor of the ASCE Journal of Bridge Engineering

  • 2015
    -
    Now

    Editorial Board Member of International Journal of Earthquake and Impact Engineering

  • 2019
    -
    2021

    地震工学会  副会長

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