Press straightening in fabrication process of orthotropic steel decks is carried out to correct deformation after welding between deck plate and U-shaped rib. Although excessive loading may be given around the welded joints, the local strain condition has not been clarified. In this study, stress measurements of orthotropic steel decks while press reforming were carried out. In addition, thermo-elasto-plastic stress analyses and residual stress measurements were carried out to clarify the residual strain around the welded joints. Moreover, fatigue test was conducted using an actual scale specimens to investigate the fatigue behaviors.

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Structural function abilities of steel plate girder bridges with corrosion damages are not clear yet sufficiently. This paper reports the results examined analytically for girder shear strengths by referring to the data of web plate thicknesses measured for the steel plate girder bridge damaged severely by chloride attack during 28 years. The models of the web plate with the corrosion aspects measured were analyzed using elastic-plastic finite element approach. The effectiveness of the corrosion aspects on the girder shear strength is revealed through comparison with available measurement data of the corroded web plate thicknesses.

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The low cycle fatigue tests of low yield strength steel shear panel damper (LYSPD) are carried out under a constant amplitude sin wave to verify the ductility performance. Four shear strain amplitudes (20%, 30%, 40% and 50%) are applied to the LYSPD in the static and dynamic loading based on three kinds of periods (static, 2 sec and 1 sec). The hysteretic characteristic, fatigue life and failure mode are obtained and compared between the static and dynamic tests. Although the dynamic test results showed that the LYSPD has large deformation capacity as well as high energy dissipation ability and good low cycle fatigue performance, these characteristics are deteriorated with the high temperature caused by high strain speed and intemal friction. In order to evaluate the dynamic performance of LYSPD rationally, the strain speed and high temperature should be taken into consideration.

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In this study, the authors propose a non-base-plate circular column base of concrete filled steel tubes(CFT) by using the built-in high strength reinforcing bars. The base plate and anchor bolts are omitted in this column base, but the high strength reinforcing bars are inserted from the CFT column to the foundation. Six specimens are tested under reversed cyclic horizontal loads while subjected to a constant axial load. The elastic-plastic behavior, the stress transfer mechanism and the bending strengths of the column bases are investigated. The results indicate that the non-base-plate column bases by using built-in reinforcing bars have excellent seismic performances.

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Where a shear panel damper with low yield strength steel sustains dead and live loading, it is necessary to estimate the influence of the vertical boundary condition on structural characteristics of the damper. In previous experimental studies, the hysteretic performance of shear panel damper was verified under constant continuous vertical loading.
On the other hand, under horizontal loading, the vertical deformation of shear panel damper is restricted by the structural frame. In order to evaluate the influence of fixed vertical displacement, static loading tests of shear panel damper under fixed vertical deformation were conducted.

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In this study, fracture toughness of existing steel highway bridge members was investigated by CTOD and Charpy Impact tests, and critical crack length, at which fatigue crack shifts to the brittle fracture, was discussed. Critical CTOD value, δc became 0.058mm(-30℃) and 0.027mm(-50℃) based on the lower value obtained by the CTOD tests (4 bridges) and Charpy impact tests (13 bridges). Based on δc, critical crack length was estimated for fatigue crack growth at web gusset welded joints of steel I-girder bridges.

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The scallop had been usually set at the connection between deck plate, transverse rib and trough rib because of avoiding the intersection of weld lines. However, the scallop was specified not to be set because of avoiding fatigue crack from the scallop. Then, fatigue cracks initiating at the weld roots between deck plates and trough ribs and propagating into deck plates were detected. In this study, fatigue tests on model specimens of the connection between deck plate, trough rib and transverse rib in steel orthotropic deck have been performed in order to examine the fatigue crack initiating and propagating behavior and the influence of deck plate thickness and existence of scallop on fatigue durability.

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This research is concerned with steel frames combined with conventional braces. Lot of research works has clarified effect of hysteretic dampers on seismic response already. However, effect of conventional braces on seismic response have not been made clear yet. In this paper, steel frames with and without conventional braces are designed in order to compare with their seismic responses. The difference of seismic response of the two kinds of frames is investigated on maximum story drift angles by seismic response analyis with fishbone-shaped frame model. By comparing the two kinds of frames，the effectiveness of the conventional braces is assessed.

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One of typical fatigue cracks observed in orthotropic steel deck plate is the crack along the weld bead between trough rib and deck plate. It is also reported that the crack sometimes changes its direction suddenly, and propagates to the rib wall and the deck plate. The propagation mechanism of the crack, however, has not been fully investigated. This study carried out a numerical study for the crack at rib-to-deck joint in the orthotropic steel deck plate. Stress intensity factors for three deformation modes were estimated by the FEA and the displacement extrapolation method with the maximum energy release rate criterion. Based on the analysis results, the crack growth mechanism and the reason why the crack changes its direction were discussed.

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This paper describes a structural design system of steel deck slabs. They have three types of slab, although each type of slab is different from others. The system has function of comparison design dealing with three types of steel deck slabs. Typical design of the steel deck slabs was demonstrated and discussed with some examples. This paper concludes that the new system is good for education of structural design.

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The material characteristics of steels are different according to the manufacturing period. In the maintenance of many aged steel railway bridges, it is important to understand the material characteristic of the aged steels. In this study, the material tests were executed for steel material of the various manufacturing period to investigate the material characteristic. In addition, the influence of a given prestrain on the strength and the impact toughness of the aged steels were clarified.
As a result, it was found that the impact toughness of the aged steels decreased as increasing of the given prestrain than that of the recent steels.

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