リム ソーポーケム (リム ソーポーケム)

写真a

所属

理工学術院 創造理工学部

職名

講師(任期付)

学位 【 表示 / 非表示

  • Waseda University   Ph.D.

 

研究分野 【 表示 / 非表示

  • 構造工学、地震工学   Concrete material and structural engineering

研究キーワード 【 表示 / 非表示

  • Concrete structural engineering

  • Concrete material engineering

  • FE modeling

  • X-ray technology

  • Steel fiber reinforced concrete

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論文 【 表示 / 非表示

  • 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年11月  [査読有り]

     概要を見る

    © 2020 Elsevier Ltd 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年09月  [査読有り]

     概要を見る

    © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. 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

  • 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年08月  [査読有り]

     概要を見る

    © 2019 Elsevier Ltd 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

  • 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年  [査読有り]

     概要を見る

    © Federation Internationale du Beton (fib) - International Federation for Structural Concrete, 2019. 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.

  • 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年  [査読有り]

     概要を見る

    © 13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2019. All rights reserved. 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.

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特定課題研究 【 表示 / 非表示

  • Effects of casting methods and flow-properties of self-compacting concrete on tflexural behavior of fiber reinforced concrete beams using X-ray images

    2019年   Ramiz Ahmed Raju, Takumi Kageyama, Syunsuke Amano, Mitsuyoshi Akiyama

     概要を見る

    The effect of concrete casting methods and concretemixes having different fiber contents (i.e., 20 kg/m3 and 40 kg/m3)on the fiber distribution and orientation as well as the structural performanceof self-compacting concrete fiber reinforced concrete (SCFRC) beams were experimentally investigated. In the experimental program, twocasting methods were designed for pouring the concrete into the same beam molds:case 1, concrete cast from a large 35-degree-slope chute into the entire mold atonce, and case 2, concrete cast from a long pipe. It was found that, with thesame casting method, SCFRC beams with fibercontent of 40 kg/m3 showed lower segregation of fibers but fibersare less aligned to the concrete flow than other beams with fiber content of 20 kg/m3.On the other hand, the casting method of case 1 inducedthe larger velocity of concrete flow than that of case 2. Fibers distribute andorientate better in direction of tensile stress in beams in case 1 due to the larger flowvelocity than that in case 2. Therefore, the structural performance of SCFRCbeam with casting method of case 1 is found to be moderately better than thatof case 2.

  • 22020構造工学および地震工学関連

    2018年   Mingyang Zhang, Mitsuyoshi Akiyama, Dan M. Frangopol

     概要を見る

    This research aims to study effects of currentdensity on the spatial steel corrosion and to assess the residualloading capacity of corroded RC beams using finite element (FE) analysis. TwoRC beams were corroded using current density levels of 50 and 500 μA/cm2.The spatial growth in steel weight loss in RC specimens was quantified atdifferent corrosion levels using X-ray and image processing techniques. Theexperimental result shows that low current density (50 μA/cm2) induced more non-uniformsteel corrosion than the high current density (500 μA/cm2). Gumbel distributionparameters were derived from the experimental results to approximately modelthe spatial variability of steel weight loss which is used as the input into FEmodel of corroded RC beams. The FEanalysis result of the RC beam that has rebar samples generated by the Gumbel distributionparameters associated with lower current density provides a more scattering andlower yielding load capacity, compared with that from a specimen with higher currentdensity.

  • Effects of fiber distribution and orientation on the flexural performance of steel fiber reinforced normal and self-compacting concrete beams

    2018年   Ramiz Ahmed Raju, Sopokhem Lim, Takumi Kageyama, Mitsuyoshi Akiyama

     概要を見る

    This experimental research presents an effort toimprove the structural performance of fiber reinforced concrete members byutilizing the high-flowability and self-placability properties of self-compactingconcrete to achieve better distribution and orientation of fibers. In the experiment, self-compactingfiber reinforced concrete (SCFRC) was flown into beam molds while steel fiberreinforced concrete (SFRC) with normal concrete was cast into other same-size beammolds. X-ray images were taken over the length of each beam to investigateeffects of flow and normal casting method on the distribution and orientationof fibers. The bending tests were performed to study the flexural performanceof SCFRC and SFRC beams. It wasconfirmed the distribution and orientation of fibers in SCFRCbeams were better than those in SFRC ones since most fibers werealigned to the high flow. As a result, the flexural performance of SCFRCbeams was superior to those of SFRC ones. However, it is challenging to attaina uniform distribution of fibers over the entire beam length. Furtherresearch is needed to find an optimum combination of concrete flow, fiberamount, and casting method by which a uniform distribution of fibers can beachieved over the entire beam length.

 

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