The imaginary parts of the Fourier transform of a causal acceleration time history can be reproduced from the real part by using the Hilbert transformation. Based on this well known fact we develop a method to simulate a causal acceleration time history. First we extract a mean trend from the root square of the real part process. Dividing the real part by this mean trend we obtain a new process, which is named as the standardized real part. After proving that this process has had a stationary characteristic we extract the probabilistic characteristics from this standardized real part process. We then develop a method to simulate a sample process of the standardized real part. Multiplying the mean trend to this stationary sample of the standardized real part process we can obtain a sample real part process. Appling the concept of the Hilbert transform to this sample real part process we can obtain the imaginary part of the causal acceleration time history. By the inverse Fourier transform of a sample real part process with the causal imaginary part we can simulate many samples of the causal acceleration time history

 Many cases of undercoating corrosion occurred at the early stage after repainting have been reported in the steel structures, mainly caused by the residual corrosion products containing salts on the steel substrate. A high-power continuous wave (CW) laser cleaning has been considered one of the effective rust removal methods applied to steel plates. However, there are no fundamental studies on the surface characteristics of steel substrate after the CW laser surface preparation. This study aims to conduct an essential examination of the surface characteristics of steel treated with a high-power CW laser. The objectives of this study are the laser-irradiated steel, and the steel blasted after laser irradiation, conducting the surface roughness measurement, metallographic analysis, XRD analysis, electro-chemical tests, and adhesion test on anti-corrosion coating. The results demonstrated the surface characteristics, the composition of the oxide film, the depth of the re-melted zone and heat-affected zone, the residual property of oxide film, and its corrosion resistance. The adhesion properties of paint coating and thermal spray coating were also revealed.

 High-strength bolted joints are widely used in steel bridges since they have advantages to construction, maintenance, and replacement. On the other hand, bolt axial force may decrease after tightening due to tightening method, tightening order, relaxation, traffic load, or earthquake. The remaining axial force of high-strength bolts is a factor that includes uncertainty therefore, it is important to evaluate the remaining bolt axial force. In this study, in order to evaluate the remaining axial force of high-strength bolts non-destructively and simply, a new remaining axial force evaluation method based on eddy current measurement was constructed. In the eddy current measurement, the stress change can be obtained by using the relationship between the magnetic permeability and the stress. Therefore, authors proposed the method considering the stress state of the bolt head and simply install the eddy current probe on the bolt head. In addition, considering that the bolt head is deformed by the axial force, the relationship between the output signal and the gap between the probe and the measurement target, which is an important evaluation index in eddy current measurement, has clarified, and the influence of the axial force evaluation has also investigated.

 A seismic retrofitting method, where the cover concrete of RC piers is replaced with the ultra-high-strength fiber-reinforced mortar (FRM) has been developed. This method may improve the deformation capacity of RC piers without increasing the cross-sectional size and weight. In this study, the behavior of the retrofitted area and the longitudinal bars ware examined based on the results of cyclic loading tests on RC pier model specimens in previous study, and a method to evaluate the deformation capacity of the retrofitted RC piers was proposed. The validity was confirmed through the comparison to the experimental results and the plastic buckling analysis of the longitudinal bars.

 In this study, the elastic modulus of CSG and its dependence on the confining pressure were clarified by triaxial compression tests and pressuremeter tests. The results of these material tests were verified by a reproduction analysis of the dynamic behaviors of Apporo Dam during an actual earthquake. By analyzing 30 seismic records of the dam, the dynamic characteristics of the dam were clarified. New findings were obtained regarding the dynamic characteristics of the new-type dam originated in Japan. In addition, after checking the internal and external stability of the Apporo Dam with the results of the reproduction analysis, it was reconfirmed that the trapezoidal CSG dam has excellent seismic resistance.

 High-order local vibration modes over 200 Hz of steel railway bridges with complicated vibration mode shapes are related to noise along the railway. However, they have not been fully elucidated due to restrictions on the number of sensors and synchronization accuracy. In this study, authors utilized a new method for identifying higher-order local vibration modes that can be implemented in field tests by substituting multipoint hammering for multipoint measurements using the reciprocity theorem and phase standardization method. Thereafter verifying the accuracy, it was applied to the steel railway I-shaped girder bridge members with direct fastening track system, and it was clarified that the vibration modes can be identified up to about 1200 Hz, which is high-order and complicated such as 7th order of the web. In addition, by analyzing with the measured responses under train passages, it is empirically demonstrated that the high-order local vibration modes of 200 to 600 Hz are superior due to the resonance with the excitation frequency caused by the periodic rail irregularity in the target bridge.

 This paper examines application of a fatigue evaluation method for the cracks in the weld joints between a U-rib and a deck plate in orthotropic steel bridge decks. Field measurements were conducted in two sections with different crack initiation trends, and a method was proposed to obtain the cumulative fatigue damage ratio from the measurement results and routinely obtained data such as temperature and traffic volume. In addition, the validity of the evaluation of crack initiation and propagation direction by the developed evaluation method is verified by comparing with the actual crack situation, and a method to screen out the priority inspection and investigation area is proposed.

 When tsunami hits a coastal area, it is important to evaluate the impact load due to the collision of tsunami debris. On the other hand, there is no method for evaluating the impact load of fishing boats, which is a problem in tsunami resistance design. Most of them are made of FRP. Therefore, in this study, in order to evaluate the effect of the collision of FRP boats, we conducted the impact experiment by free fall using an actual boat and got its fracture behavior and impact load. Then, by reproducing this experiment by FEM analysis, we investigated the construction of the method that can evaluate the collision phenomenon of FRP boats by numerical simulation.