Deterioration of existing bridges has become a severe problem and seriously affect the serviceability and durability of railway system in many countries. A preventive maintenance strengthening method using rubber-latex mortar, Glass Fiber Reinforced Polymer (GFRP) plates, lightweight rapid hardening concrete, and reinforcement was introduced this study, which can be used to strengthen the both steel bridge superstructures and bridge piers. In order to confirm the real effects of the present strengthening method, field loading test on a short-span railway bridge and laboratory tests on a steel column were performed. The results on both original and strengthened specimens were summarized and compared. For the railway bridge superstructure, theoretical results were also provided to confirm the strengthening effects. For the steel piers, however, numerical models were built to provide the load carrying capacity of the original pier. The load-displacement curve and load-strain response at key sections were measured in the loading tests and reported in this paper. According to the results, the present renovation method could greatly enhance the rigidity of old steel railway bridge superstructures and the load carrying capacity of existing piers, resulting in the extension of the residual service life of short-span railway bridge superstructures and improvement of seismic behavior of steel piers.

Steel-concrete composite twin l-girder bridges have been built a lot in both Europe and Japan, but the lack of redundancy has always been a concern in U.S. and many other countries. In addition, few experimental studies have been performed on the mechanical performance of such bridges, particularly for the intact bridges. On this background, a steel-concrete composite twin l-Girder bridge model was designed according to the current highway bridge design specification in Japan and tested in the laboratory. The static loading tests were performed, and two loading conditions including both symmetrical loading and unsymmetrical loading were applied. Load versus deflection relationships were measured in the loading test, and the failure mode of the test specimen was discussed. The flexural strain development on bottom flanges of two main girders was also reported in this paper to confirm the load transfer between two main girders. In addition, the theoretical results on the basis of the classic theory were also provided to compare with the test results. The comparison indicates that the theoretical analyses can predict the behaviour of the twin l-girder bridges very well in the elastic stage by considering the effective width of the slab. The load transfer paths in such bridges were also discussed on the basis of the test results under un-symmetrical loading.

Deterioration of aging bridges is a serious problem that affects their serviceability and durability. Appropriate repair, strengthening, or replacement work should be performed on aged bridge structures to ensure they remain in good condition. A novel strengthening method using rubber-latex mortar, glass-fiber-reinforced polymer plates, lightweight rapid-hardening concrete, and reinforcement bars is proposed in this article. The strengthening method can be used to strengthen both steel railway bridge superstructures and piers. To confirm the effectiveness of the strengthening method, field tests on a short-span railway bridge and laboratory tests on longitudinal-lateral beam connections and steel piers were performed. Because the structural stiffness of aged steel structures is directly related to the fatigue performance and the seismic behavior of steel piers, the applied load versus displacement and strain responses of the test specimens were of primary interest in the tests. Strain results at key sections were experimentally measured and are reported in this paper. According to the experimental results, the present renovation method can significantly enhance the rigidity and reduce the stress levels in bridge girders, connections, and piers, resulting in the extension of the residual service life of such structures. (C) 2017 American Society of Civil Engineers.

Techniques for structural repair and maintenance are becoming increasingly important because of increasing problems associated with aging structures. This paper introduces a method for strengthening aged steel columns by using new construction materials such as glass-fiber-reinforced polymer (GFRP) plates, rapid-hardening concrete, rubber-latex mortar, and reinforcing bars. The purpose of the present study is to investigate the mechanical performance of steel columns before and after strengthening, thereby assessing the effectiveness of the proposed strengthening method. Depending on the possible directions of applied load (major axis or minor axis) and the corrosion conditions, three specimens were employed in the loading tests. Static loading tests were performed on steel columns with and without strengthening. Test results, including load-deflection relationships and the strain development process of the columns, were measured and compared between the original and strengthened columns. Moreover, three-dimensional finite-element models were built to compare the strengthened and original steel columns. Both the experimental and numerical results indicate that the proposed strengthening method can significantly enhance the stiffness in the elastic stage and the load-carrying capacities in the plastic stage, resulting in significant extension of residual service life under real service conditions and improvement of seismic performance during earthquakes. (C) 2017 Elsevier Ltd. All rights reserved.

An experimental program was performed to investigate the postfracture performance of composite twin I-girder bridges in the fatigue crack condition. An intact specimen and a damaged specimen were tested under one-point load to understand the effect of fracture on the bridge response and safety. In addition, nonlinear numerical analyses were performed to study the mechanical behavior of the models. The results showed that the fracture of the entire web and bottom flange at the midspan section can result in a considerable increase in the shear strain on the studs near the middle section. The fracture of the bridge in the midspan section governed by bending failure is found to be most critical in terms of the remaining load-carrying capacity, and the fracture near the support location governed by shear failure is found to be brittle, which can result in a sudden collapse of the bridge system. The effects of the fatigue crack on the safety of the composite twin I-girder bridge can be mitigated by using a continuous span instead of a simply supported span or by using a stronger and thicker concrete slab. (C) 2017 American Society of Civil Engineers.

This study is carried out to investigate the post-fracture behavior of the composite twin I-girder bridge systems. In the experimental program, one intact specimen and one damage specimen were tested under static load with displacement control method. Different cases of fractures are performed in numerical analyses based on finite element method and nonlinear analyses. Significant reduction of system stiffness and load carrying capacity is observed in post-fracture condition. The failure modes of both intact and damage specimen are governed by the crush of the concrete slab. Nevertheless, composite twin I-girder bridge system will not collapse under dead load and be able to carry a certain level of live load. Numerical analyses for different damage conditions proved that the fracture at mid-span section is the most fracture critical location for composite twin I-girder bridge system.

In the next 20years, more than half of the bridges in Japan would be in service for more than 50years. These include truss bridges those are generally consideredto benon-redundantand fracture critical. With ageing, these bridges are facing an increasing risk of bridge collapse under extreme conditions.Therefore, it is essential to evaluate alternate load paths on existing bridge structures to avoid bridge collapse or replacement. In this paper, after-fracture redundancy of truss bridges is investigated through a case study for a five-span continuous truss bridge. Field tests were performed, and the displacements on key sections were measured in the test. According to the experimental observations and test results, a numerical model capable of simulating the present truss bridge was built and was used to investigate the after-fracture redundancy of the target bridge. Fracture of truss members in typical locations was considered in the numerical analyses, and the R' values of both intact and damaged trusses were compared. On the basis of the numerical results, a critical member in this bridge was also determined.

The Kintai-kyo Bridge is a unique, five-span wooden bridge with three arches across the Nishiki River, the largest river of the Yamaguchi Prefecture, Japan. The central wooden rib arch is very rare in the world. The bridge has become a famous landmark because of its elegant structure and its aesthetic appearance that is in harmony with the surrounding picturesque landscape. It is a popular historical site and attracts many tourists. The wooden bridge has been rebuilt several times since its inauguration in 1673. The latest rebuilding was done in 2004 which was almost 50 years after the previous one. The original span length of the Kintai-kyo Bridge was close to the limit allowed for construction of wooden bridges during that time. In order to strengthen the bridge against floods, the best combination of wood and stone was used. Arch structure was adopted for the superstructure, and hollow stone piers of spindle-shaped cross-section were adopted in the substructure. This paper studies the origin of the arch structure of the Kintai-kyo Bridge because this arch is unique and different from the voussoir arch or the corbel arch, and its resulting elegant appearance. In addition, as a unique feature, periodical inspections of the Kintai-kyo Bridge have been conducted by the Waseda University every 5 years since 1953, where the weight of local high-school students is used as the load for testing.

The effects of the inclination angle on the buckling of continuous composite bridges (CCBs) with parabolic arch ribs remain to be elucidated. Static tests were conducted on an on-site prototype of a CCB with parallel arch ribs to verify the validity of proposed numerical finite element method models of CCBs with inward and outward arch ribs. We found that the expressions for the equivalent slenderness ratios and buckling coefficients should consider the interactions between the in-plane and out-of-plane buckling, given the inclination of the arch ribs. With respect to the buckling modes, the arch ribs of all the models buckled in the first lateral mode. In addition, two types of interactions were observed between the buckling modes, namely, that between in-plane and out-of-plane buckling and that between global and local buckling; these were affected by the inclination angle, especially in the case of the CCB with the outward arch ribs.

Gusset plates of a joint in a steel truss bridge are the key parts of the structure system, because they are connecting several main truss members. However, the detailed failure mode of gusset plates subjected to compression has not been well examined yet. Therefore, this paper discusses the failure mechanism of the gusset plates of a joint subjected to compressive force through the diagonal member. The failure mode is examined by both numerical and experimental method. And It is clearly shown that the failure mode demonstrated by these two methods are quite consistent with each other. Then, a strength equation for the gusset plates subjected to compression is finally created on the basis of the failure mode.

Bridge accessories, such as parapets, service ducts, and track slabs, are commonly used in railway bridges, but their real effects on the structural behavior of the bridges are still unknown because very few studies have been reported on this significant aspect. In engineering practice, lack of information on the contribution of bridge accessories may cause problems for bridge design, bridge health evaluation and monitoring, bridge management and operation, and bridge maintenance. Given this background, field tests were performed on a railway bridge with typical bridge accessories to confirm their contribution to bridge rigidity (or stiffness), as well as their effects on the sectional normal strain distribution. Both displacements in the midspan and strain results on key sections were measured in the field test and reported in this paper. Based on the field test observations, a numerical model capable of simulating the present railway bridge was built and was used to investigate the effects of the bridge accessories and their expansion joints. Longitudinal normal stress distributions on concrete slabs, steel main girders, and single-parapet panels were given, and parametric analysis considering different arrangement methods of expansion joints in the bridge accessories was also performed. Based on the numerical results, a stress concentration on the concrete slab near the expansion joints was confirmed. The results obtained in this study can be used for improving the design method used in new railway bridges and the maintenance of old railway bridge structures. (C) 2015 American Society of Civil Engineers.

Perfobond connectors are a certain type of shear connectors used in steel and concrete composite structures. In composite bridges with narrow connector distances or shallow rib heights, it is unfavorable to enhance shear connection by using large circular-hole perfobond connectors. To solve this problem, an alternative perfobond connector was developed by making long-holes on steel rib plates. In this paper, 21 push-out specimens were fabricated and loaded to failure. The main objective was to compare the failure mode, shear capacity and slip behavior of perfobond connectors using circular-holes and long-holes. Furthermore, 87 nonlinear finite element simulations were performed to further study the effects of hole geometry and concrete strength. The parametric results were generated to evaluate the shear capacity equations for perfobond connectors. Finally, an analytical model was proposed to predict the shear strength of both circular-hole and long-hole perfobond connectors. (C) 2015 Elsevier Ltd. All rights reserved.

As the national bridge inventory ages and traffic volumes increase, the government is spending more on maintaining their existing structures to extend the service life of the current bridge inventory. This includes two-girder bridges that are classified as fracture critical and non-redundant. Owing to the increased inspection costs associated with these fracture-critical bridges, there is a need to evaluate alternate load paths and to implement retrofit methods on existing bridge structures to avoid bridge replacement. In this paper, after-fracture redundancy of two-girder bridges is investigated through a case study for a four-span continuous steel-concrete composite twin boxgirder bridge. The finite element analysis was carried out to evaluate the load-carrying capacity after failure of one girder of the two-girder bridge. Two types of the main-girder damage, including fracture of the bottom flange only, and fracture of both bottom flange and the web were considered respectively in this study. Typical damage locations including mid-span section of the main girder and the sections near the intermediate support were also considered in the numerical analyses. On the basis of the numerical results, the present continuous steel-concrete composite box-girder bridge was classified as a redundant bridge, and the concrete deck was considered as the key member for ensuring the bridge redundancy after severe damages occurred on the main girders.

This research offers a new composite revamping method for railway bridges by assuming composite remodelling process of existing steel bridges having no specific fissure damages or serious corrosions and effectively making use of relatively new materials to it. Effects of noise reduction and improved stiffness were further confirmed through hammer impact tests (vibration measurement tests) and loading tests in order to prove the efficacy of the composite remodelling.

In steel and concrete composite girders, the load transfer between the steel beam and the concrete slab is commonly ensured by installing shear connectors. In this paper, to investigate the nonlinear behavior of perfobond connectors, a total of 60 push-out specimens were fabricated and tested with the variables for the hole diameter, the concrete strength, the thickness of concrete slab, the diameter, strength and existence of perforating rebar, the thickness, height and distance of perfobond ribs. The failure mode and the load-slip behavior of perfobond connectors were obtained. A theoretical model was put forward to express the load-slip relationship. Analytical formulas of shear capacity and peak slip were also proposed considering the interaction between the concrete dowel and the perforating rebar. The calculation results of the proposals agreed well with the experimental values.

Continuous composite beams represent an efficient structural form in many structural systems, such as buildings and bridges, due to additional advantages associated with the favorable redistribution of internal forces across the member and the easier satisfaction of serviceability checks. Moreover, in the regions of hogging moments, e.g. at the internal support regions of continuous members, a large part of the composite beam section is subjected to torsional moment under certain loading conditions and in curved composite structures or flyovers, thus the bottom flange and the web are susceptible to local instabilities and the concrete slab may crack during its service stage. In this study, two steel-concrete composite beams were tested to investigate their mechanical performance under combined hogging bending and torsional moments. Load and deflection relationships, strain distribution and development in the reinforcement, and the slip on the steel-concrete interface were recorded in the test and reported in this paper.

In current practice and design, composite twin I-girder bridges are predominantly used in highway bridges design due to their low cost comparing to other types of bridges. While classified as non-redundant structural system according to AASHTO specifications, previous practical experiences have shown that this type of bridges is capable of surviving some accident events such as losing of one support or sudden fracture of web and bottom flange. For this reason, an experiment was carried out to investigate the redundancy level of composite twin I-girder system. The fracture is limited to the whole web and bottom flange as the top flange is fully connected with the slab by shear connectors. Results show that after the fracture of full web and bottom flange, the composite twin I-girder bridge is still capable of carrying some load before losing its functionality and reaches the ultimate failure state. Base on the results of this study, the redundancy level of tested specimens is higher than 1.0. There for, the simply supported composite twin I-girder model in this study is concluded as a redundant bridge structure.

Bridge accessories such as parapets, duct, slab deck are commonly used in bridge structures, but their real effects on the structural behavior of the bridges are still unknown. In this study, experiments were performed on a railway bridge to confirm the contribution of the bridge accessories and their design details. Both displacements on key sections and sectional strains were measured in the test, and the theoretical results on the basis of the classical mechanics were provided to compare with the test results. In order to evaluate actual stiffness of the bridge, numerical studies were conducted, and the stress concentration on the concrete slab near the expansion joints was confirmed. The results obtained in this study can be used for improving the design method of new railway bridges and maintenance of old railway bridge structures.

Redundancy is one of the most important factors to evaluate the safety of a bridge as it shows the possibility of the bridge to survive after an incident that can cause partial or full damage on the critical member of the bridge. The purpose of the present study is to evaluate redundancy level of three span continuous twin I-girder composite bridges, which is widely used in current highway bridges. Bridge models were studied and analyzed by using the finite element method with the aid of DIANA Software. Firstly, experimental results were used to verify the validity the present numerical model. Thereafter, fracture of one mid-span girder was assumed in order to determine the redundancy level of damaged bridge models. This study also shows the importance of secondary members in transferring and redistributing the load after the fracture at the mid-span of one main girder of the bridge.

This paper describes the effects of SFRC on improving the mechanical performance of composite steel and concrete beams subjected to hogging moment. Four specimens with different concrete slabs and different shear connectors were examined experimentally in this study. Steel fiber reinforced concrete (SFRC) was used for two specimens, and normal concrete was applied for the other two specimens. Different types of shear connectors, including shear studs and Perfo-Bond Strips (PBLs), were used on steel-slab interface of the specimens. Shrinkage of the normal and steel fiber reinforced concrete, load versus mid-span deflection relationship, crack formation and its propagation process, and slip development on the steel-slab interface were measured and investigated. The test results show that the inclusion of steel fibers decreased both the crack sparing and crack width of the concrete slab. The specimens with steel fiber reinforced concrete have relatively large initial cracking load, and crack width of the concrete slab can be controlled appropriately in the service stage. The effects of the SFRC on the ultimate load carrying capacity of the beam depend on the shear connectors applied on the steel-slab interface. The application of SFRC could enhance the load carrying capacity of the specimen with stud shear connectors, however, the effects of SFRC on the load carrying capacity of PBL specimen were found to be declined in some extent. Besides, the current specifications, such as AASHTO, EUROCODE-4 and JSCE, are typically conservative in predicting the ultimate load carrying capacity for composite beams under hogging moment. (C) 2014 Elsevier Ltd. All rights reserved.

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The horizontally curved continuous composite steel-concrete beams, for instance, curved continuous composite bridges, have excellent qualities, such as quick construction, good seismic performance, saving construction formwork and convenience in spatial arrangement etc. At present, the application research of this kind of structures is becoming more of a concern, but very few studies have been conducted to study the mechanical performance of composite beams subjected to combined hogging (negative) bending and torsion. The purpose of the present study is to investigate the effects of curvatures on both elastic and inelastic behaviours of curved continuous steel-concrete composite beams in the interior support regions. Based on the experimental observations in a straight composite beam, a three-dimensional FE model capable of analysing the composite beams subjected to negative bending moment is built. Further numerical studies on curved composite beams with different curvatures are performed in this study. Strength and load carrying capacity, sectional strain distribution and movement of composite neutral axis before and after cracking, as well as the strain results of longitudinal reinforcing bars are investigated. Besides, the interaction equation for ultimate bending and torsional moments is proposed.

Preventive maintenance on aged steel railway structures is all important due to their long service time after completion. This paper introduced a strengthening method for old steel railway bridges by using rubber-latex mortar, glass fiber reinforced polymer (GFRP) plates, lightweight rapid hardening concrete, and reinforcing bars. Both laboratory tests and field tests were performed to confirm the effects of the present strengthening method. In total, two old railway bridges were employed in this study. One of them has been in service for around 100 years. The static loading test was performed in the laboratory. Experimental results, including load-deflection response, strain distribution on the structural steel, GFRP plates as well as concrete, were given and compared between the original steel railway bridge and the strengthened bridge. Theoretical results were also provided to make a comparison with the experimental results. Both the experimental and theoretical results indicated that the present renovation method could greatly enhance the rigidity and reduce the stress levels of old steel members, resulting in the extension of the residual service life of the old steel railway bridge. In addition, field tests were performed on the other old railway bridge, which has been used for 86 years, and stress variation on the railway bridge under the running train was measured and the effects of the present strengthening method in the real service condition were also confirmed.

Bridge Redundancy Evaluation is getting more attention in both designing new highway bridges and repairing or retrofitting old bridges after several bridge collapses or failure incidents happened around the world in recent years. This study is tempted to evaluate effects of secondary members on redundancy of three-span composite twin I-girder bridge. Two types of secondary members were studied including I-shape transverse beams and L-shape X-type bottom lateral bracing. Results show that three-span composite twin I-girder bridge can be considered as redundant. The redundancy level can be increased by adding bottom X-type lateral bracing. I-shape transverse beams alone is found not effective in increasing the redundancy of the bridge, but is found useful to increase the efficiency of the bottom X-type bracing to increase the load carrying capacity and redundancy of bridge.

As the bridge inventory ages and traffic volumes increase, the bridge owners are spending more on maintaining their current structures. AASHTO considers virtually all two-girder bridge systems as non-redundant, and each girder is considered as the fracture-critical member (FCM). Redundancy analysis of the two-girder bridges considering the uncertainty (damage scenarios) is investigated through a case study on a three-span, continuous twin I-girder bridge. The FE analysis is employed to evaluate the load-carrying capacity after fracture of one main girder of the twin girder bridge. The damage locations are chosen at the mid-span section of the middle span, the side span, and the section near the continuous pier support. Damage to shear connectors near the moment contra-flexure regions and missing one bearing at the middle and end support locations are also considered as potential damage scenarios in this study. On the basis of the direct redundancy analysis results, the present continuous two-girder composite bridge can be classified as redundant.

Structural repairing or maintenance technique has been a hot issue in recent years due to the increasing aging problems of old railway bridges. A strengthening method for welded joints in old steel railway bridges by integrating the rapid hardening concrete, rubber-latex mortar, and reinforcing bars is introduced in this paper. The purpose of the present study is to investigate the mechanical performance of the strengthened connection joints in old steel railway bridges. Depending on the locations of the concrete and possible loading conditions, the joint needs to sustain both negative and positive bending moment, therefore, two experimental plans were employed. The static loading tests on the steel joints before and after strengthening were performed to confirm the effects of the present strengthening method. Moreover, three-dimensional FE models were built to make a comparison study between the strengthened and original steel joints. Load versus deflection relationship and strain development process on the web of the joints were measured and compared between the original joints and the strengthened joints. Both experimental and numerical results indicate that the present strengthening method can greatly enhance the stiffness and reduce the stress levels of steel joints, resulting in the extension service life of aged steel railway bridges. (C) 2013 Elsevier Ltd. All rights reserved.

A partially encased composite l-girder with flat or corrugated web has been proposed to improve the structural performance of continuous composite girder under hogging moment. The flexural behavior of such structure under two points symmetric loading has been experimentally and analytically investigated. Static flexural loading tests showed that the partially encased girder improved bending strength in comparison to steel I-girder, as local bucking of steel flange was restricted by encased concrete. Especially for the corrugated web girder, the ultimate bending strength was improved about 20%, and the ductility also increased about 3 times. In addition, the limitation of width-to-thickness ratios for steel and concrete-encased composite I-girders with corrugated web were suggested to prevent premature failure due to local buckling of compressive flange. Moreover, the analytical methods of flexural strength under service and ultimate state for partially encased composite girder were proposed and verified with experimental results. It was found that the analytical bending strengths agreed well with the experimental ones at both service and ultimate state, which means the proposed analytical equations can be applied in predicting flexural strength accurately for such encased composite girder with flat or corrugated web. (C) 2013 Elsevier Ltd. All rights reserved.

Limited experimental results have been reported in the literature on the fatigue and ultimate static loading behavior of composite beams subjected to negative bending moment. This paper examines experimentally the behavior of composite steel-concrete beams. Eight composite specimens were tested to study the various aspects of composite beams under a negative bending moment, including the effects of repeated loading, shear connectors (studs and PBLs), rubber-latex mortar coating, and steel fiber-reinforced concrete (SFRC) on their structural performance. Load versus midspan deflection, crack formation and its developing process, slip distribution on the steel-slab interface, and the flexural strain results of shear connectors were measured and studied. The test results show that the initial cracking-level repeated load did not show obvious effects, while the stabilized cracking-level repeated load can reduce the rigidity and loading capacity of composite beams. The experimental results indicate that the plastic bending moment criteria in the current AASHTO load and resistance factor design specifications are typically conservative for composite beams under a negative bending moment. In addition, the effects of SFRC on crack width control and adhesion bonding effects of rubber latex on the steel-slab interface were confirmed in the testing. (C) 2013 American Society of Civil Engineers.

In continuous steel-concrete composite structures, cracking of the concrete slab in the hogging bending moment region decreases the global stiffness of composite structures and reduces the effect of continuity, resulting in making the structural behaviors highly nonlinear even for low stress levels. Because of this, special consideration is necessary. The purpose of the present study is to investigate the effects of rubber-latex mortar and different types of shear connectors on inelastic behavior of composite girders subjected to hogging moment. Two overturned simply supported steel-concrete composite girders with different shear connectors such as Studs and Perfo-Bond Strips (PBLs) were tested under concentrated load in the mid-span. Based on the experimental observations, a three-dimensional FE model capable of analyzing the composite beams subjected to negative bending moment was built. Strength and load bearing capacity, sectional strain distribution and movement of composite neutral axis before and after cracking were observed in the test and compared with the numerical results, and the results predicted by this modeling method are in good agreement with those obtained from the tests. Research results indicate that the PBL connectors could slightly improve the rigidity of the composite girder under both the serviceability limit state and the ultimate limit state, while Stud specimens have relatively better mechanical behavior in regard to the initial crack and the "crack closure" of the test specimens. Besides, research results indicate that the current specifications such as AASHTO, JSCE, and EUROCODE-4 can provide appropriate values for ultimate strength of a composite girder under negative bending moment. Moreover, noise reduction, shear stud stiffness increase and the adhesion bonding effect of rubber-latex mortar on interface slip were confirmed in the tests.

As the Japan bridge inventory ages and traffic volumes increase, the government is spending more on maintaining their existing structures to extend the service life of the current bridge inventory. This includes two-girder bridges that are classified as fracture critical and non-redundant. Owing to the increased inspection costs associated with these fracture-critical bridges, there is a need to evaluate alternate load paths and to implement retrofit methods on existing bridge structures to avoid bridge replacement. In this paper, fracture redundancy of the two-girder bridge is investigated through a case study for a three-span continuous twin I-girder bridge. The finite element analysis is carried out to evaluate the load-carrying capacity after fracture of a girder of the two-girder bridge. Damage of studs near the moment contra-flexure regions are also considered in this study. Spacing between the transverse beams is discussed as possible techniques to improve redundancy and reduce the fracture potential of two-girder bridge structures. The concrete slab is indicated to be a significant member for guarantying the redundancy of the two-girder steel-concrete composite bridges.

Structural repair or maintenance technique has been a hot issue in recent years due to the increasing aging problems of old railway bridges, which have been used beyond or approaching their design service life. A strengthening method for old steel railway bridges by integrating the new structural members was adopted in engineering practice in this context. Rubber-latex mortar, GFRP plates and rapid hardening concrete were integrated with the old steel railway bridge to increase its rigidity and reduce both stress levels and structure-borne sound levels of the old steel bridge. The purpose of the present study is to investigate the mechanical performance of the renovated hybrid railway bridge. The material test on aged structural steel, the static loading test on the strengthened bridge, and the impact hammer test on the old bridge before and after strengthening, were performed to confirm the effects of present strengthening method. Moreover, three-dimensional FE models were built to make a comparison study between the strengthened and the original steel bridge. Both experimental and numerical results indicate that the renovation method can greatly enhance the stiffness and reduce the stress levels of steel members, resulting in the extension of the service life of the old steel railway bridge. Furthermore, noise reduction effects by using concrete and rubber-latex mortar were confirmed in the impact test. (C) 2013 Elsevier Ltd. All rights reserved.

This paper describes the fatigue behavior of composite steel and concrete beams subjected to negative bending moment. Fatigue tests with repeated load limited to initial cracking and stabilized cracking, were performed on two steel-concrete composite beam substructures respectively. Test results indicated that when the repeated load was equivalent to the initial cracking load, the fatigue test had only limited influence on beam stiffness or crack patterns. However, when the repeated load was equivalent to the stabilized cracking load, a number of residual cracks occurred in the initial static test and the beam became less stiff as the load cycles increase. Failure of the bond between studs and surrounding concrete was confirmed in intermediate static tests; flexural stiffness of studs became smaller as the increase of load cycles. In addition, final static tests were performed on fatigue test specimens and another specimen without fatigue test. The comparison indicated that when the repeated load was larger than the initial cracking load, fatigue test could decrease beam stiffness and its ultimate load carrying capacity. (C) 2012 Elsevier Ltd. All rights reserved.

Shear behavior of partially encased composite l-girders with corrugated web has been investigated analytically and numerically in this paper. A 3-D finite element model with geometric and material nonlinearity is established and verified by the experiments. Subsequently, a parametric study is carried out to examine the effects of geometric and material properties on the shear behavior which includes corrugation, height, thickness, connection degree between steel web and concrete encasement. It is found that the ultimate shear strength of steel l-girders is improved with increases in the thickness, height and yield strength of corrugated web, while the ultimate shear strength of partially encased composite I-girders increases with the thickness, yield strength of corrugated web and the thickness, compressive strength of concrete encasement. However, the stud stiffness has little influence on the ultimate shear strength. Moreover, the concrete encasement improves the shear strength of steel l-girders, the degree of improvement increases with the thickness and compressive strength of the concrete, but decreases drastically with the thickness of corrugated web. Therefore, it is suggested that concrete should be poured on the corrugated web with thin thickness or low yield strength to prevent buckling occurrence before yielding of steel web. Finally, shear strength prediction equations are proposed and verified by numerical results. The calculated shear strength agree well with the numerical results for steel l-girders before and after composite with concrete, which indicates that the proposed analytical equations can be applied to predict the shear strength of such partially encased composite girders with corrugated web. (C) 2012 Elsevier Ltd. All rights reserved.

A new type of partially encased composite I-girder with corrugated steel web has been proposed to improve the structural performance of continuous girders under hogging moment. The shear behavior of such partially encased composite I-girders under anti-symmetric loading has been experimentally and analytically investigated. Experimental results show that the partially encased composite girders has superior shear strength compared to steel I-girders, since shear bucking of steel web is restricted by concrete encasement. The shear stiffness of the composite section is based on the total summation of corrugated web and concrete encasement with average thickness before cracking, and the ratio of shear resistance shared by the steel web and the concrete encasement depends on their shear stiffness. In addition, predicted shear strength of the partially encased composite girder with corrugated web is proposed according to the experimental failure mode and strain distribution. The analytical shear stiffness and shear resistance ratio at the elastic stage are verified by experimental results. And the calculated shear strength for steel and composite girders agree well with the experimental results. The comparison shows that the proposed analytical methods can be applied in predicting elastic shear stiffness and design shear strength for such partially encased composite girders with corrugated web. (C) 2012 Elsevier Ltd. All rights reserved.

The composite bridges with corrugated steel webs have excellent properties, such as lightness of girders, efficiency of introducing prestress forces, short construction period, optimum force distribution, good seismic performance, and aesthetics appearance etc., which have greatly promoted the application of such bridges. The objective of this paper is to provide and summarize important references related to the analysis, design and construction of composite bridges with corrugated steel webs. Subjects discussed in this review include (1) structural configuration and application; (2) shear behavior; (3) bending behavior; (4) torsional behavior; (5) patch loading resistance; (6) dynamic behavior; (7) long-term behaviors including fatigue and creep; (8) component connections; (9) analysis method and theory; (10) new concept application. The literature survey presented herein mainly focuses on papers written in English, Japanese, German and Chinese in relation to composite bridges with corrugated steel webs.

Maintenance of existing steel structures has been a hot issue in recent years. A hybrid bridge was created from an original steel structure by integrating with the concrete members. The purpose of the present study is to investigate the mechanical behavior of the renovated girder. Based on the experimental observations, a three-dimensional FE model capable of analyzing these kinds of composite structures was built. Strength and deformation response, sectional strain distribution and movement of composite neutral axis before and after concrete cracking were observed in the test and compared with the numerical results, and the results predicted by this modelling method are in good agreement with those obtained from the tests. Results indicate that the renovated structure can greatly enhance the stiffness and reduce the stress levels, resulting in the extension service life of the structure.

The important accidents that the diagonal members of the steel truss bridge have broken due to severe corrosion damages occurred recently. Therefore it is expected to establish the rational and efficient maintenance management technique depending on the bridge type and structure characteristic. Especially, the corrosion damages of the main members may have a serious influence on the safety of the bridge system, and the technique for the investigation and checking is appropriately demanded. In this study, for the corroded gusset plate connection which was cut out from the steel truss bridge, we measured the corrosion shape in detail using the surface roughness measurement equipment, and evaluated the actual state by the surface corrosion of the outside and the narrow inside of the gusset plate connection.

In continuous composite steel-concrete structures, cracking of the concrete slab in the hogging moment region decreases the global stiffness of composite steel-concrete structures and reduces the effect of continuity, thus making the structural behaviour highly nonlinear even for low stress levels, so special consideration is necessary. An experimental investigation on the behaviour of steel-concrete composite beams in hogging moment region is presented in this paper. A total of four specimens were tested under point load in the mid-span. Two of the composite beams with headed studs as the shear connectors, while the other two specimens are using Perfo-Bond Strips (PBLs) as the connection devices between the steel girder and the concrete slab. Ultimate load bearing capacity of composite sections in negative moment region was calculated and compared with experimental values. Crack formation, crack widths development process and strain distribution of the composite section before and after cracking were observed and presented in this study. Interface slip distribution was also given. Research results indicate that the current specifications such as AASHTO, JSCE, and EUROCODE-4 can provide appropriate values for ultimate strength of a composite girder under negative bending moment.

The horizontally curved composite girder bridges have excellent properties, such as quick construction, good seismic performance, saving construction formwork and convenience in spatial arrangementetc, which have greatly promoted the application of such bridges. The objective of this paper is to provide and summarize important references related to the analysis, design and construction of curved composite girder bridges. Subjects discussed in this review include (I) different curved girder bridge configurations and their applied range; (2) current specifications; (3) construction issues; (4) design methods; (5) analytical methods; (6) load distribution; (7) torsional behavior; (8) warping stresses; (9) stability; (10) ultimate load-carrying capacity; (11) dynamic and seismic response; (12) loading test; (13) long-term behavior; and (14) design details. The literature survey presented herein mainly focuses on papers written in English. Japanese and Chinese in relation to curved composite girders.

Ten specimens are tested to investigate the cyclic behavior of beam-to-column joints of steel frames with joint panels. The performances of the joints with respect to strength, rigidity, and hysteretic performance are examined. Three different loadcarrying mechanisms can be identified. Panel resistance ratio (Rp) is presented for predicting the buckling patterns. The validityof Rp is confirmed through the present experimental results. On the basis of the experimental results of steel beam-to-columnmoment joints, 3-D nonlinear finite element models are established to analyze the mechanical properties of these connections.The load-displacement curves of the finite element analysis are in good agreement with those of the tests in terms of strengthand unloading stiffness. A shear lag phenomenon was captured in the beam flanges by not only experimental results but alsonumerical analysis. Parametric studies are conducted on the connections under monotonic loading to investigate the influencesof connection dimension, resistance ratio on the connection behavior. It was found that the failure modes are influenced by theresistance ratio, while the thickness of joint panels resulting in large effects on the strength and stiffness under shear failure mode. © Springer, Part of Springer Science+Business Media.

Ten specimens are tested to investigate the cyclic behavior of beam-to-column joints of steel frames with joint panels. The performances of the joints with respect to strength, rigidity, and hysteretic performance are examined. Three different load-carrying mechanisms can be identified. Panel resistance ratio (R(p)) is presented for predicting the buckling patterns. The validity of R(p) is confirmed through the present experimental results. On the basis of the experimental results of steel beam-to-column moment joints, 3-D nonlinear finite element models are established to analyze the mechanical properties of these connections. The load-displacement curves of the finite element analysis are in good agreement with those of the tests in terms of strength and unloading stiffness. A shear lag phenomenon was captured in the beam flanges by not only experimental results but also numerical analysis. Parametric studies are conducted on the connections under monotonic loading to investigate the influences of connection dimension, resistance ratio on the connection behavior. It was found that the failure modes are influenced by the resistance ratio, while the thickness of joint panels resulting in large effects on the strength and stillness under shear failure mode.

Negative bending moments acting on the support regions of continuous composite girders generate tensile stresses in the concrete slab and compressive stresses in the lower steel profile. As a result, the mechanical behaviour of these girders becomes strongly nonlinear, which needs special study. In this paper, static experimental tests on four half-scale models of steel and concrete composite girders with different shear connectors such as studs and Perfo-Bond Strips (PBLs) under hogging moments are cautiously conducted in order to investigate the reduction of flexural stiffness and the inelastic behaviour after cracking. In the test results, crack development, crack widths and strains of the composite section before and after cracking were observed. The crack width evaluation methods based on design codes for steel and concrete composite girders under negative bending moment were compared. Crack widths should be controlled appropriately within an allowable value in the slab under service load. The strains in reinforcing bars obtained through the static tests agreed well with the values calculated through the application of the existing tension stiffening theory. The test specimens could be assumed to be a full composite section until the ultimate state on the basis of load and slip relationship results of shear connectors. It follows that analytical and experimental studies can be served as a basis for the design of continuous composite bridges. (C) 2009 Elsevier Ltd. All rights reserved.

The Kintaikyo Bridge with the five span wooden arch structures over the Nishiki River in Japan was originally constructed in 1673. Each span of the three central arches is 35.10m, the total length being 193.3m and the roadway being 5.0m wide. The arch ribs are made of keyaki wood and pine, which have high working strength, while the covering and han-drail are hinoki wood, a species of cypress. As the floor follows the curve of the arches, the Kin-taikyo Bridge is available only for a pedestrian bridge. The Kintaikyo Bridge is vulnerable to natural disasters such as floods and earthquakes. In this paper, the structural characteristics of the Kintaikyo Bridge are dealt with in detail, in which each of the central three spans of the Kin-taikyo Bridge is proved to be a real arch structure. And finally the structural preservation of the Kintaikyo Bridge is fully discussed.

The expansion joints are expected to have movement capacity, bearing capacity for static and dynamic loading, water-tightness, low noise emission and traffic safety. In particular, the failure due to impact loading is the main reason for the observed damages. The problem of dynamic behavior of the expansion joints is so complex that we shall focus our attention on the impact factor for vehicle load that is governed by traffic impact. In order to overcome this difficulty, the cantilever-toothed aluminum joint (finger joint) is one of the promising joints under impact loading. In this study, from the viewpoint of design methodology, numerical studies for impact behavior were conducted for aluminum alloy expansion joints with perforated dowels. The design impact factor for the expansion joints with the perforated dowels against traffic impact loading was examined by using numerical simulations.

This research has aimed to understand the behaviors of the crack of the RC deck slab caused by a negative bending in the middle supports of continuous composite gider bridges. For the determination of stress and strains in cracked regions, the effect of tension stiffening of concrete on stresses in reinforcement has to be taken into account. It was confirmed from the fatigue tests that the crack width approaches to a certain value with the increase of the number of repeated cycles.

This paper is concerned with the identification of bifurcation points occurring on the mechanism paths of a linkage, in which the structural system consists of links and revolute joints. The way that the links are assembled is mathematically described by compatibility conditions. The present paper mainly deals with the kinematic paths of mechanism that goes through special configurations of kinematic bifurcations. In general, Such special Configurations are called uncertainty configurations or singular configurations. The Jacobian derived from the compatibility conditions has been used as a measure of the distance away from the singular configurations. The Jacobian does not always give Sufficient results for the detection of bifurcation points. This Suggests that it is necessary to consider higher-order infinitesimals for examining approximate Solutions of compatibility conditions. The Hessian matrix derived from the Jacobi matrix is considered to be one of the promising measure and may clarify the nature of the singular configuration as to whether the system is at a bifurcation point or not. In this paper, the theory behind the kinematic bifurcation of mechanisms of a linkage is explained and the numerical analysis of illustrative examples is discussed in detail.

Firstly, failure mode and shear strength of stud connectors were investigated based on push-out test results. Secondly, the practicability of a proposed analytical method was verified on the basis of a comparison with test results and the failure mechanism of the grouped arrangement was investigated. Lastly, parametric analyses on concrete strength and on the longitudinal spacing of stud connectors were conducted and shear strength reduction equations of the grouped arrangement of stud connectors were proposed.

In order to design and construct new type hybrid structures, more general time-dependent-analysis is needed. Then we propose an exact method for time-dependent-anlysis in this paper, in which the changing of centroid axis due to construction sequence in cross section and time-dependent behaviors such as creep and shrinkage of concrete. And it adopts the step-by-step method and the successively integral method, which is not influenced by a form of predicting formula in creep of concrete. Furthermore it assumes the parabolic strain distribution in the members for calculating the end-forces such as creep and shrinkage of concrete, and relaxation of prestressing steel. At last due to the numerical examples, the restraint effect of steel in concrete and the influence degree of changing of centroid axis are presented.

The authors have proposed an equation for estimating the ultimate strength of T-shaped socket joints. However, the effect of cyclic loading and external diagphragms, applicability to the cross-shaped joint and other issues must be verified. Therefore, the static loading tests by using the T-shaped joint specimens were carried out in order to investigate the effects of loading method and the diaphragm. Monotonic static loading tests by using the cross-shaped joint specimens were also carried out. The test results indicate that the loading method and the diaphragm affect the ultimate strength, and that the application of the proposed method to the cross-shaped joint is promising.

For sleeve joints between concrete-filled circular steel tubular column and steel beam, authors carried out the monotonic static loading tests by using the T-shaped joint specimens, and have proposed an equation for estimating the ultimate strength. However, an application of the equation to an actual structure needs to consider the effects of cyclic loading and the diaphragm, including the application of the proposed method to the cross-shaped joint. Then, in addition to the monotonic static loading tests, the static loading tests by using the T-shaped joint specimens were carried out in order to investigate the effects of loading method and the diaphragm. Moreover, the monotonic static loading tests by using the cross-shaped joint specimens were also carried out. The test results indicate that the loading method (cyclic or monotonic) and a diaphragm affect on the ultimate strength, and that the application of the proposed method to the cross-shaped joint is promising.

A dynamic response analysis method for evaluation of the maximum and residual displacements of steel piers or frames with box sections is proposed. A &ldquo;plastic deteriorating hinge&rdquo; is defined as a deteriorating area in the stiffened plates, which is due to local buckling. The buckling stress, the softening stress-strain relation and the decrease in unloading stiffness of a plastic deteriorating hinge are formulated from FEM studies with shell elements, and they are implemented in the stress-strain relation of a beam element.<br>The maximum and residual displacements of steel frames are successfully predicted by finite displacement analyses with such beams, which can be used for evaluation of seismic performance of existing steel frames.

This paper deals with load carrying capacity of corner joints between concrete filled steel columns and beams, with the help of loading tests and FEM analyses. For the loading tests, the model tests were carried out on four specimens by changing the position of stiffeners, the cross-section of beams. In the FEM analyses, six models were compared with each other to supplement the loading tests. As a result, it was found that each filling concrete in the corner hollow section has a constantly strong effect on the ultimate strength of cornerjoints regardless of whether the ring stiffeners are applied or not. The loading tests also confirmed that filling concrete circular steel pipes used for beam members were expected to two times post-yielding ductility to that of the filling concrete rectangular section member, the hollow circular section one.

This paper deals with load carrying capacity of corner joints between concrete filled steel columns and beams, with the help of loading tests and FEM analyses. For the loading tests, the model tests were carried out on four specimens by changing the position of stiffeners, the cross-section of beams. In the FEM analyses, six models were compared with each other to supplement the loading tests. As a result, it was found that each filling concrete in the corner hollow section has a constantly strong effect on the ultimate strength of cornerjoints regardless of whether the ring stiffeners are applied or not. The loading tests also confirmed that filling concrete circular steel pipes used for beam members were expected to two times post-yielding ductility to that of the filling concrete rectangular section member, the hollow circular section one.

The composite girders are mainly used for bridges, in which cracking of concrete slab plays an important role. Crack width is calculated by using strain of reinforcement and crack interval. In this study, a new calculation technique for the estimation of the strain is proposed with EC 4. Moreover, simplified analysis for steel fiber reinforced concrete (SFRC) is also proposed. The proposed technique is validated by comparison with experiments of girders with the shaft tension.

Synopsis: The study is aimed at obtaining basic data for evaluating the residual strength and deformability of damaged reinforced concrete members.
The behavior of members that suffered damage during cyclic loading such as cracking that penetrate into the cross section, plastic deformation or partial failure was compared with that of member tested under simple torsion. Reversed cyclic torsion was applied for loading because few studies have been reported in open literature although it has been estimated to cause the most brittle failure.
Tests and analyses identified the effect of reversed cyclic torsion with varying numbers of cycles and with varying amplitudes had on the reduction of residual strength and torsional rigidity. It was also confirmed that a closed joint that encircles longitudinal reinforcement at the ends of transverse reinforcement was stronger and more resistant to deformation than a lapped joint.

The continuous composite girders are mainly used for bridges. Cracking of concrete slab plays an important role near the intermediate supports where the negative bending moment occurs. Crack width is calculated by using strain of reinforcement and crack interval. In EUROCODE 4, the shaft tension model is developed for the analysis of negative bending behavior, and the crack width is calculated from the model. In this study, a new calculation technique for the estimation of crack width is proposed with the help of crack interval given by Japanese specification and strain of reinforcement determined by EC 4. The proposed technique is validated by comparison with experiments of girders with the negative bending moment.

After Hyogoken-Nanbu Earthquake in 1995, pounding between the adjacent girders is of major concern from the view point of base isolation. In this paper, an experimental study using the two-dimensional shaking table was performed focusing on the dynamic and impact behavior of the pounding between the adjacent girders. The girder falling was observed due to the pounding between the adjacent girders. The effects of the pounding on the falling girders were examined by the response acceleration of the girders and deformation of the piers. The effects of the shock absorber such as rubber and lead inserted to the bridge restrainer plates in order to decrease impact force were investigated.

By narrowing the box girder width, it is expected that overall costs will effectively be reduced. Moreover, by increasing slab thickness, it is possible to omit stringers in addition to decrease the box girder width. Thus box girder fabrication productivity and bridge durability are greatly improved. If torsional rigidity of the box girder is decreased and the floor slabs became thicker, the amount of required cross-beams can be also reduced.<br>This paper is concerned with an analytical study focusing on the following points: (1) the validity of omitting cross-beams in the narrowed box girder bridges and (2) in which MSC-NASTRAN was utilized throughout to conduct 3D finite element analysis.

The purpose of the present study is to investigate a long term behavior of new type connections which have punched holes with transverse steel reinforcing bars inserted into a concrete flange. Experiments and FEM analysis were carried out for several types of specimens changing plate thickness and embedded depths of corrugated steel webs. Experimental results reveal that the present connection is promising from the view point of practical application.

This paper reports an experimental study on the mechanical behavior of concrete slabs at the intermediate supports of axially prestressed continuous composite girders.<br>Static loading tests were carried out on the concrete slab subjected to negative bending in order to grasp the mechanical behavior of the continuous composite girders. Attention is paid to the differences of mechanical behaviors in terms of manufacturing concrete slabs, prestressing and intervals of studs. It turned out from the experimental study that prestressing for concrete slabs plays a key role for reducing cracks due to negative bending.

The purpose of the present paper is to demonstrate a nonlinear dynamic response analysis of steel bridge piers under seismic loading, in which a simplified model is employed as a constitutive equation and the effects of local buckling on the global cyclic plasticity of steel bridge piers are examined. On the basis of the fact that local buckling of steel component plates during earthquakes reduces the stiffness of steel bridge piers and cyclic loading degrades the strength of the steel piers, a simplified method for nonlinear dynamic response analysis of hysteretic steel bridge piers is investigated by using a pertinent one dimensional model.

A method of analysis for the solutions of transient wave propagation in an infinite thick plate on elastic foundation is developed in terms of eigenfunctions depending on the Fourier integral transforms. The Winkler assumption that the reaction forces of the foundation are proportional at every point to the bottom bounding displacements of the plate touching the foundation is taken here. The time history of displacements and stresses representing the head of the disturbance are evaluated as transient wave propagation corresponding to different speeds of concentrated moving loads that are suddenly applied at the free surface of the plate standing still initially.