Many Fatigue cracks have been detected in beam-to-column connection in steel bridge frame piers of highways and the cause and measures are looked for. In this study, the fatigue testing was executed by using the full-scale specimen that reproduced the local stress and the welding at the three welding line intersection part as well as the existing bridge.
  As a result, it was shown that the main factor of the fatigue strength decrease was both of peculiar welding defect (delta-zone) and the welding surface defect at three welding line intersection part in beam-to-column connection. Moreover, the bridge frame piers where a lot of cracks occur have been produced using the steel from 1960’s to 1970’s and cannot apply the repair welding. Therefore, it proposed the repaired large core method, and the petrofitting method showed that fatigue strength in the existing beam-to-column connection was able to be improved greatly.

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  This study investigated on the cause of brittle fracture during earthquakes from the viewpoint of structural peculiarities focusing on the stress triaxiality. The target structure is the actually fractured steel rigid bent of a highway bridge. From the investigations using nonlinear finite element analysis, it was confirmed that high stress triaxiality was generated at a point supposed as fracture origin depending on the geometry of weld bead, in which the level of stress triaxiality at the point increases in the case of bead toe radius is small or two bead leg lengths are unequal.

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  In the seismic design of reinforced concrete bridge piers, earthquake motion is considered separately in the longitudinal and transverse directions. Actually, however, earthquake motion in either direction is expected to act on the structure simultaneously. It has been reported that simultaneous action of earthquake motion is likely to cause greater damage to bridge piers than in the case where earthquake motion in either direction is considered separately. To use precast ultra-high-strength fiber-reinforced concrete (UFC) forms for the bottom regions of reinforced concrete bridge piers is expected to reinforce the concrete cover in the plastic hinge region and achieve high seismic performance against bilateral ground motion. In this study, a reinforced concrete bridge pier using precast UFC forms was subjected to bilateral cyclic loading and the seismic performance of the bridge pier against bilateral earthquake motion was identified.

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  In Japan, a steel-plate concrete composite deck which is connected concrete and a steel-plate with shear studs, is called Robinson type. In order to decrease deflection of the steel plate when fresh concrete is casting on, the steel plate is stiffened with steel strips. In recent years, the composite deck is applied to many high way bridge decks. The objective of this paper is to propose a performance-based design method for the composite deck that founded on the results of researches conducted by the authors. Specifically, performance and functional requirements for bridge decks are considered, and design traffic loads and partially safety factors peculiar to bridge decks for performance verifications are evaluated. Furthermore, examples of performance verifications of actual composite decks are carried out. In conclusion, the proposed design method enables the composite deck within a long span range to reduce its thickness approximately 20% compared with the standards of conventionally design method.

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  On steel railway bridges crossing over roadways, collision accident occur frequently with large vehicles such as mobile crane and induce halting train service. When the accident occurs, the section men should judge immediately reopen service or continue halting after urgent inspection the damages. In case of serious damage such as girder deviation from shoes and rails bending horizontally, breaking of lower flange, continuous halting is judged until finish of repair works. But, in the case that the damage is only deformation of lower flange part such as local bending or sway deformation, the section men worry to judge reopen or halting because there is no clear basis for the decision. In this study, the boundary amounts of the local deformation damages are proposed through material tests for the damage part steel and numerical investigation of load carrying capacity of girders having such local deformation damage.

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  Maximum displacement under actual loading is an essential indicator for performance evaluation of existing structures. However, direct measeurement of displacement requires fixed reference point, and its implementation in actual civil structures are generally difficult and costly, while acceleration can readily be measured for wide variety of situations. Hence, fast evaluation method for maximum displacement response from acceleration response based on random vibration theory is proposed in this paper. First, arithmetric equations to express relationship between response acceleration and response displacement is derived from response statistics in random vibration theory. Then, the accuracy of the method is evaluated through numerical simulations and actual measurement data at the Akashi-Kaikyo Bridge, and its applicability is verified.

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  Steel-concrete hybrid PC Langer bridge, which consisted of RC arches, vertical steel tube hangers and PC stiffening girders, was constructed. Three dimensional numerical simulations of steel-concrete connection between the RC arch and the vertical steel tube hanger was conducted for the future establishment of verification technique of joint connection in hybrid structures using finite element method. The assembled finite element model was verified with sufficient accuracy for the mechanical behavior of the test specimens of the connection subjected to pull-out load in the steel tube. Furthermore, based on the result of numerical investigation on the partial model of joint connection, it was numerically confirmed that the ultimate state of the connection in the actual hybrid bridge was governed by the flexural capacity of its RC arch and that the connection had a sufficient resistance to the applied pull-out load through the vertical steel tube.

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  The formation of a fracture process zone (FPZ) often observed at meso-scale structures of quasi-brittle materials such as concrete and other cementitious materials is simulated with a discrete fracture analysis method to clarify the underlying mechanism that characterizes the corresponding macro-scale behavior. After formulating the discrete fracture analysis method, which we have developed to simulate the softening behavior of concrete with the help of the cohesive crack model, we explain the numerical modeling of micro-crack behavior in consideration of material inhomogeneity at meso-scale together with energy-based fracture mechanics. Two representative numerical examples are presented to demonstrate that the interactions of crack nucleation, coalescence, opening and closing eventually leads to a crack in the meso-scale FPZ and that the macro-scale fracture toughness is characterized by the distributions of multiple micro-cracks.

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  This article examined an effectiveness of the Structural Health Monitoring methods based on vibration characteristic changes for steel truss bridges where damage accidents occurred successively. At first, vibration characteristics of the truss bridge are investigated by both theoretical and experimental modal analyses, for paying attention to the coupling of diagonal members in global vibration modes of truss bridges. By using the vibration data of car running test on the truss bridge with the damage in the diagonal member, the possibility of damage detection is next examined based on the change in the damping of diagonal member-coupled mode.

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  In order to ensure the seismic safety of railway system, it is important to consider the following points. First, we have to investigate the safety of the railway structures such as bridges, viaducts, embankments and so on, which spread extensively. Second, we should consider not only the safety of structures but also the vehicle running safety. In this study, we have developed the methodology to predict the seismic damage of railway structures and the seismic running safety of the railway vehicle using only four parameters, which are peak ground acceleration, peak ground velocity, yield strength, and equivalent natural period. We have proved the efficiency of the newly developed method by simulating the structural damages and derailment of Shinkansen-train in the 1995 Hyogoken-Nanbu earthquake and the 2004 Niigataken-Tuetu earthquake.

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  The earth retaining composite wall consisting of the soil-cement wall core (H-section steels) and the sidewall of reinforced concrete structure (RC) in cut and cover tunnel can reduce the construction cost, the amount of excavated soil due to the use of core (H-section steels). This paper proposes the method of connection between the core and RC sidewall by using Perfobond strip as shear connector. In order to evaluate the seismic performance and loading capacity of this composite structure, the loading tests of composite beams and corner joint members are conducted. The composite beams between H-section steels and RC connected by Perfobond strip are tested to confirm its unity and capacity. For corner joint members (L-shape specimens), the seismic loading tests are performed, and the effective arrangement of reinforcing bars under the seismic load is proposed.

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  Conventional damage predictions methodologies of lifeline structures are mainly based on peak ground motion measures. However a line structure such as a lifeline suffers damage mainly induced by the strain of the ground, and therefore is likely to be vulnerable to sharp spatial changes in ground motion. In this study we propose a measure of water supply pipeline (WSP) damage based on the spatial gradient of peak ground velocity (PGV), as an attempt to quantify the effect of geospatial variability of ground motion into lifeline damage. We investigated the spatial distribution of damage to WSP during the 2004/10/23, M6.8 Niigata-ken Chuetsu earthquake, and compared the surveyed damage with the PGV distribution as well as with the gradients of PGV calculated around the source area. In order to allow a comparison between ground motions and the very dense observed damage to WSP, we calculated the PGV distribution for a region around the source area at a grid cell every 250 m. We estimated ground motions by applying a broadband frequency strong ground motion simulation methodology based on a multi-asperity source model of the Chuetsu earthquake. Then we calculated the gradients of PGV along the geographical coordinates, and define the PGV gradient vector amplitudes as a damage estimator.   Our results show that the distribution of damage to WSP has a very good correlation with the gradients of PGV, in contrast with a poor correlation with PGV. We show that the predicted PGV values and the gradient of PGV are useful indexes for a first screening evaluation of hazard maps of roads and underground facilities like WSP.

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  When a fatigue crack originates and propagates from weld root, detection of the crack is difficult. Therefore, its prevention is important from the point of maintenance view. A lot of studies have been performed on the fatigue strength of cruciform welded joints failing from weld roots under axial loading conditions. But the real structures have a lot of parts in which out-of-plane bending applies. In this study, the difference between fatigue strength when the cruciform joints sustain out of plane bending and axial force, and the fatigue strength evaluation formula under combined loads are discussed through fatigue tests on model specimens and fatigue crack propagation analyses.

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  It is reported that steel members such as arch ribs and towers of suspension bridges may be subjected to high compressive axial force during the huge earthquake like the Kobe Earthquake. However, little is known about the seismic performance of steel members under high compressive axial force. So it is very important to grasp the seismic performance of steel members under high compressive axial force.
  In this study, cyclic loading experiments and FEM analysis were conducted and the effect of the compressive axial force, the aspect ratio of the section, width-thickness ratio parameters and the other buckling parameters on the seismic performance were evaluated. Furthermore, the seismic evaluation method of the stiffened steel members under high compressive axial force is proposed and the validity of the proposed method was confirmed by comparing the experimental and analysis results including the previous studies with calculated results by the proposed evaluation method.

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