A new technology has been developed for high strength bridge wires: steel wires are coated with aluminium (Al) and zinc (Zn) alloy. It is expected that the bridge wires coated with Al-Zn have higher corrosion resistance than the Zn coated ones. The steel wire with a diameter of 5mm coated with Al (10%) and Zn (90%) alloy is produced and corrosion acceleration tests have been conducted and the corrosion resistance is compared with the steel wires coated with Zn. The steel wires are kept under three different corrosion environments: kept at a relative humidity (RH) of 60%, kept at a RH of 100%, and wrapped with wet gauze which simulates the wet condition. The wire specimens are kept in the thermo-hygrostat at 40°C for 150 days.
 The mass loss due to corrosion under the relative humidity of 60% and 100% is much smaller than that under the wet environment, and there isn't much difference between Al-Zn coated wires and Zn coated wires. On the other hand, the mass loss of the steel wires coated with Al-Zn is distinctively smaller than those coated with Zn under the wet condition. The mass loss of the NaCl attached wires is twice larger than that without NaCl under the wet condition.
 The corroded wires are investigated by EPMA analysis showing that the corrosion product of Zn is loose and easy to exfoliate from the steel layer. On the contrary, the corrosion product of Al-Zn alloy is dense and hard to exfoliate from the steel layer. This difference is the reason of the superiority of the Al-Zn coated wires.

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 A comparative experimental study is presented on the cyclic behavior of steel truss structures whose diagonal members are of buckling-restrained braces (BRB) made of either steel (SM400) or aluminum alloy (A6061S-T6). The cross-sections of the diagonal members of both cases are identical (PL60x10). The test results have revealed that, due to the larger axial rigidity as well as the larger strain hardening effects in steel BRBs compared with aluminum BBBs, the truss with steel BRBs induces larger damages in the surrounding members than that of aluminum BRBs. This fact hints the favorable way of designing BRBs in real bridge structures, i.e., to avoid using excessively stiff bracing members is important.

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 Resent years, from the viewpoint of rational structural members of steel bridges, the high strength bolted friction type joints tend to be large. Since the slip behavior of high strength multi bolted friction type joints with thick plates is not clear, the slip strength tests for such joints had been carried out. And from the experimental results, it can be found that slip coefficient varies depending on the number of rows of bolts in a line. In this study, in order to clarify the slip behavior of such joints, FE analysis has been conducted with various structural dimensions, such as slip/yielding strength ratio, section shape of the connected plate etc. As a result, the slip coefficient of the joint with many bolts in a line becomes low because each frictional force per one bolt is unequal, and the plate width effects on the slip strength more significantly than other structural dimensions.

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 For the joints with phosphate treatment surfaces of hot-dip galvanized coating, hot-dip galvanized bolts are applied and such bolts are tightened by turn-of-nut method. However, it is unclear how much axial force is induced into the bolts in this joint. The slip coefficient with phosphate treatment surfaces of hot-dip galvanized coating is not also clear. To clarify the induced axial force of the bolts, bolt-tightening tests were carried out. Considering bolt diameter, bolt length, induced axial forces and their relaxation, nut rotation angles are proposed in relation to different bolt size in this paper. In order to examine slip coefficient of the bolted joints with phosphate treatment contact surfaces slip tests of high strength bolted joints were carried out. On the basis of above examinations, the slip coefficient with phosphate treatment surfaces is clarified.

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 Scatter in fatigue life of welded joints is estimated by using crack propagation analysis based on probabilistic fracture mechanics and Monte Carlo simulation. The scatter observed in fatigue tests can be well simulated when not only the variations of parameters used in crack propagation analysis but the uncertainty of the crack propagation analysis are taken into account. In the end, an example of determination of the fatigue design curve with small number of fatigue tests is demonstrated.

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 The ultimate strength of aluminum alloy plates in in-plane shear is investigated by the elastic-plastic large deflection analysis with FEM. The aluminum alloys taken into account are heat-treated alloys A6061-T6 and A6005C-T5 and non-heat-treated alloy A5083-O. The residual stresses and initial deflection caused by joining and the strength-reduction at joints in heat-treated 6000 alloys are considered in the analysis. It is shown that the upper limit of the ultimate strength of rectangular plates with joints of heat-treated 6000 alloys is the 0.2 % shear proof stress of the joints. Based on the results of the analysis, the ultimate strength curves are provided for rectangular plates in in-plane shear.

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 Some of the hydroelectric stations take a role to supply electric power to the thermal power stations as restarting power generation. Therefore, it is an important subject to continue the function of the hydroelectric station at the time of an earthquake occurrence. On the other hand, if the facilities of the lower stream of a regulating reservoir are safe in earthquake disaster, by using storage water of a regulating reservoir, we can generate electricity for a while. That is, a regulating reservoir has a role of buffer effect, then it can play an important role in supplying electric power to the thermal power stations. In this paper, we proposed the evaluation method of the system reliability and restoration curve for the hydroelectric station with buffer effect of a regulating reservoir. In evaluation, a damage correlation of components is considered. To evaluate the performance of method, it is applied to an actual hydroelectric station, and buffer effect of a regulating reservoir and the influence of the damage correlation are discussed.

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 Displacement has been regarded as the key indicator for health monitoring because it is closely related to running safety of trains and other structural performances of bridges. However, direct measurement of displacement is often difficult and costly because it generally requires fixed reference points. On the other hand, inertia measurements is expected to be applied for practical heath monitoring, because it has capability of wide variety of installation environments. From this point of view, we have developed evaluating methods of displacement based on the acceleration records. Developed method intended to earthquake response which does not contain high frequency components or random response, such as wind load and microtremor. In this paper we extend the method for train load which is necessary to consider not only the characteristics of the specific structure but the characteristics of the periodic external force. Proposes a theoretical basis on how to take into account periodic external force of the load train to estimate the maximum displacement from the acceleration response and verify the effectiveness of the method from the simulation and field test results at actual railway bridges.

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 In this study, a methodology for the displacement response estimation based on the acceleration response observed on the railway bridges under passing train loads by applying the sequential data assimilation was proposed. In particular, The linear dynamic analysis using finite element models was included in the framework of the merging particle filter which is one of the sequential data assimilation techniques, and the methodology which corrects a simulation model and its output sequentially by the acceleration response was constructed. Through the application to numerical computations and field tests targeting a RC simple beam and a RC rigid-frame bridge, It was confirmed that although a problem remains in the estimation of a modal damping ratio, the proposal methodology could estimate the displacement response at the time of a train running with sufficient accuracy on both bridges.

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 The authors proposed a new method for shear connection between concrete and perforated steel plate using cylindrical connectors such as high strength mortal cylinder and mortal filled steel tube (MFT). Direct shear test of the connector and push-out test of perforated plate connected to concrete using the connectors were conducted. The results shows that shear capacity of mortal cylinder linearly varied with compression strength of mortal, and that of connection using MFT could be evaluated as a summation of the values of shear strength of steel tube and internal mortal cylinder. Further, secant stiffness and residual slip displacement at a shear force to the 1/3 shear capacity were close of connection with perfobond strip.

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 This study is intended to investigate feasibility of bridge health monitoring utilizing dynamic parameters and a linear system parameter of a time series model identified from traffic-induced vibration data of bridge through a moving vehicle experiment on a real continuous steel-truss bridge. In addition to the natural frequency and damping constant of the bridge, this study adopts Damage Indicator (DI) which consists of autoregressive (AR) coefficients as a parameter to detect possible anomaly of the bridge. First, this study assesses the changes in frequency, damping constant, mode shape and DI. Second, Mahalano-bis-Taguchi System (MTS) is used to judge potential changes in frequency, damping constant and DI. DI can be estimated stably and its change due to damage is relatively large. Mahalanobis-Taguchi System (MTS) is successfully applied to make a decision on not only bridge condition but damage location. Observation demonstrates feasibility of structural diagnosis of bridges from the identified system parameters. However, the sensor location is still an important factor in identifying damage location which needs further investigations.

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 This paper discusses the generating mechanism of tsunami hydrodynamic force acting on a plate girder bridge through hydraulic experiments. The hydrodynamic force, the pressure and the flow pattern around the model were observed. Further, the effect of countermeasure performed on a plate girder bridge model with baffle plates was discussed. Just after tsunami hit the bridge model, pressure acting on the streamwise overhang of the bridge deck generated upward lift and head-up moment. A short time after, the flow through the model caused positive pressure on the upper surface of the model and generated downward lift force. Installing vertical baffle plates to the bridge, lift force was decreased though drag force was not changed. Installing triangle baffle plates to the bridge, drag force was decreased while only small effect was found.

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 As an effective measure against fatigue cracks of existing orthotropic steel decks (OSDs), steel-fiber reinforced concrete (SFRC) overlays have been used for existing damaged OSDs. For the purpose of evaluating the retrofit performance under severe service condition, shear bond strength tests of epoxy adhesive layer at deck-to-overlay connection with small size specimens, and wheel running tests with an actual size OSD specimen with SFRC overlay were carried out. Also, tentative manual for design and construction of SFRC overlays was developed to ensure reliability of durable performance. In this paper, outline of the design method is introduced, and the results of confirmation tests for the durable performance are reported.

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