This paper discusses the hydrodynamic tsunami-induced force acting on a bridge superstructure based on hydraulic model experiments and numerical simulations. Hydraulic experiments were conducted with using models of box girder bridge to clarify the influence of tsunami wave shapes to tsunami wave forces acting on it. Experimental results showed that tsunami wave forces were different according to the shape of tsunami incident wave, even if the maximum tsunami height and the tsunami velocity were the same and it was confirmed that maximum wave forces could be expressed as a function of the wave front slope of tsunami incident wave. Furthermore, the numerical simulations were conducted to reproduce the results of the hydraulic model experiments. As a result of simulations, it was found that while wave forces when a tsunami collided to a bridge girder corresponded with the experimental results by a twodimensional simulation, in order to evaluate wave forces when a bride girder was submerged, it was necessary to reproduce the three-dimensional structure of vortex around the cross-section by a three-dimensional simulation.

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 The cross section of box culverts for road has recently become large and been complicated, which makes it difficult to evaluate the seismic limit states of these box culverts. This research focuses on the limit states of the box culverts for the seismic performance design based on a series of cyclic loading tests for 1/3 scaled models. The failure mechanism of the box culverts under cyclic loading was observed during the tests, where the damage developed on both outside and inside faces was monitored so as to discuss the seismic limit states of the box culvert structure. Furthermore experimental results of the cyclic loading tests for the box culverts were simulated by the two-dimensional frame analysis. An applicability of the frame analysis was discussed through a comparison of analytical results with experimental observations.

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 Fatigue strength for root failure in fillet weld joints is conventionally estimated with nominal stress in weld throat. This idea is applicable only when the nominal throat stress is clearly obtained. This paper presents a new fatigue strength evaluation method for root failure, based on displacement at unfused zone around weld root. An advantage of the use of the displacement, instead of stresses, is low sensitivity to finite element mesh in FEA. We propose a method to use the displacement at the spot 1mm away from the root on unfused zone surface, obtained by FEA with 1mm size elements, as a parameter for fatigue strength evaluation. The results of analytical and experimental verification on load-carrying cruciform joints, butt joints and out-of-plane gusset joints demonstrate that the displacement based method can evaluate the fatigue strength of root failure with the accuracy equivalent to that of throat stress method.

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 We propose a porous hood for a high-speed railway tunnel to reduce a micro-pressure wave. This proposal is based on a prediction method of a micro-pressure wave, which simulates pressure wave generation by a train entering into a hooded tunnel and its propagation along a tunnel and then evaluates the discharge of a micro-pressure wave from an exit of a hooded tunnel. The predicted results agree well with field measurement data. By using this prediction method, we study the effects of a porous aperture ratio and the length of a porous hood on the strength of a micro-pressure wave and find their critical values to fulfill the requirement of a micro-pressure wave strength. These parameters are then adjusted under the constrains of the noise emission from the porous hood and the construction cost of a porous hood. Finally, we present a standard configuration of a porous hood for a high-speed railway.

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 We proposed a simple evaluation method of the waveform at the surface of the ground by using both the natural period of the ground and the waveform at the engineering bedrock. In this research, the "Equivalent Single Degree of Freedom method" was proposed based on the results of the static push-over analyses of many grounds with various properties. We compared the waveforms of the multi-layered ground obtained from the proposed method with the dynamic analysis. We then confirmed that those waves are almost identical, and the proposed method is applicable to the evaluation of the surface motion. Despite the existing railway line has only a few soil properties available, the proposed method enables the dense calculation of the surface motions alongside the line in an economical manner. These sets of waveforms will be utilized to identify locations where devastating damage is expected under strong earthquakes.

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 A new type of post for the bridge beam-type railing has been developed using the extruded multi-follow-type shape of aluminum-alloy to have the improved landscape and permeability following the bridge railing specifications. First, dynamic impact tests using a steel heavy ball and numerical analyses simulation have been performed for model posts made from aluminum alloy plate to determine the multi-hollow-type sectional dimensions. Then, extruded posts have been tested and analyzed to prove the dynamic performance. The new type of aluminum-alloy extruded post has a good performance even subjected to the dynamic impact using a heavy steel ball. Finally a collision analysis has been done between a vehicle and a newly developed railing to prove the safety and guide performance.

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 The redundancy analysis is used to check the performance of bridges after sudden failure of their tension members. The current redundancy analysis is mainly based on a linear static analysis where the dynamic effect due to the sudden failure of the tension members is approximately considered by the socalled impact coefficient (i.e. dynamic to static ratio). This implies that the current redundancy check is done by the strength check method within the frame work of the allowable stress design. Therefore, the only way for the current redundancy analysis to improve the redundancy of bridges is to increase the strength of their members. However, the increase in member strengths will result in the increase in dynamic effects and may cause metal fracture in connections. In addition, it will be costly to improve the redundancy of structures by just increasing the strengths of members. Herein, an energy-based redundancy analysis is presented to take into account the energy dissipation capacity of the truss bridges due to the plastification of remaining members after the failure of some members. This energy dissipation capacity is utilized to reduce the dynamic effect. The proposed energy-based redundancy analysis is practical because the energy dissipation capacity is statically evaluated by the pushover analysis. By the use of the proposed method, the redundancy of structures may be improved not only by the increase of member strengths but also by the increase of the energy dissipation capacity.

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 The innovative steel column integrated by multiple steel pipes with shear link dissipaters was proposed based on damage control design during earthquake. An experimental study was conducted on four types of shear links, each utilizing different connection methods as well as welding joints, bearing-type connection and friction joints. The main objectives of the large-scale experiments were to apply cyclic plastic deformations and evaluate damage process and ultimate failure mode of the shear link components. Experiments of specimens utilizing welding joints and bearing-type connection resulted in ductile hysteretic behavior showing suitability as shear link dissipaters. In the link where friction joints were used, the failure mode initiated with cracks in the web at the splice region of friction joints and propagated along bolt holes of friction joins leading to progressive tearing and failure. The ultimate failure mode was found to significantly vary among all of the specimens, with different connection methods.

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 Dynamics of a full-scale tank station yard, which consists of several in-ground tanks and soil foundation, is computationally simulated by using 3D nonlinear finite element analysis, and the mutual interaction of some adjacent tanks and the seismic response accelerogram at sites are compared with onsite measurements for verification. It is confirmed by using a confinement-dependent soil constitutive model, detailed ground boring data and the one for multi-directional cracked concrete that the coupled tank and soil foundation model of full 3D extent brings about realistic and reasonable simulation. The group effect of tanks is found to cause complex ovalling deformation of each. Further, safety assessment of group tanks is conducted based upon the verification of the ultimate limit state which is codified in the structural performance code for practice, and the structural safety is verified with reasonable safety margins.

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 Recently, many kinds of welding materials were widely used in fabrication of steel bridges. It was considered that the quality of these welding materials has been remarkably improved. However, chemical compositions of the material is not clarified. In this paper, we have investigated the 638 of welding materials on the basis of the mill sheet in order to clarify their quality. Investigated component were Carbon, Silicon, Manganese, Phosphorus, Sulfur, Copper, Chrome and Nickel, and these results were shown. We also showed difference in the quality, comparing with the conventional steel data, which were SM490Y, SMA490W, SM570Q and SMA570W.

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 In order to realize appropriate bridge maintenance, it is important that we grasp the load acting on the bridge and the response. There is a problem of the overloading vehicle on bridges in urban expressways.
 In this study, we developed the monitoring system using optical fiber sensor having all automatic realtime processing functions including Weigh-in-Motion, and the system was applied to Metropolitan Expressway. Then the behavior of the bridge was monitored for a long term. The load and the response to fluctuate in the short term and in the long term was analyzed.

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