The difficulty of modeling underground structures is a bottleneck in quantitatively studying earthquake phenomena. Stochastic modeling that accounts for the uncertainty of modeling is an alternative, and the authors have been developing two analysis methods for a stochastic model. This paper presents these methods in a unified manner, emphasizing the efficiency of numerical computation. The earthquake wave propagation and the surface earthquake fault formation are solved as examples, and the results are compared with observed data to examine the validity and limitation of the analysis methods of the stochastic model.

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In post structures supporting traffic signs or lighting apparatuses on highway bridges, strengthening gussets welded at the bottom of post introduce stress concentration and make these details susceptible to fatigue failure. Stress and deformation near critical points in normal and improved type post structures are comprehensively studied with 3D finite element analyses. Fatigue evaluations are carried out with HSS method and one-millimeter stress approach based on finite element analyses. Fatigue strengths are suggested based on test data and evaluations. It is found that one-millimeter stress approach is suitable for fatigue evaluation of post structures and that thickness correction is necessary in HSS method evaluations.

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A numerical procedure for crack width evaluation of steel-concrete composite girder bridges under negative bending moment is proposed. The procedure is combination of 3-dimensional finite element (FE) analysis with smeared crack model and a bond-slip differential equation. From the FE analysis, the averaged behaviour including shear-lag as well as cracking is calculated. Then, the crack width is evaluated by using the differential equation and the FE results. Attention is paid to the consistency between the FE modelling and the employed bond-slip differential equation. The obtained crack widths are shown to compare well with those from experiments on composite girder specimens.

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A countermeasure against near-source ground motions should be established based on careful examinations of their characteristics. Since a tendency has been found for the strike-normal component to be predominant in the near-source region of a large intra-plate earthquake, it is expected to be a reasonable decision to orient important quay walls perpendicular to the strike of the active fault of concern. For the purpose of validating this decision, two kinds of analysis are conducted, namely, ground motion simulations to show the effects of fault parameters on the predominant direction of near-source ground motions and non-linear FEM analyses to show the effects of quay wall orientation on its residual deformation.

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With the results of field investigations and outdoor exposure experiments of painted specimens, time-lapse deterioration of paintings was statistically analyzed by using “Automatic Evaluation System for Paint Film Deterioration” in order to establish deterioration curves logically. Quadratic curves were found to be well fitted to the paint film deterioration within the practical period of 10 to 20 years. Estimation curves were established for three corrosive environments such as mild environment, seashore environment, and tropical environment (hot and highly humid).

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When a momentary pressure pulsation takes place in a turbine, and its frequency coincides with the natural frequency of a steel penstock, resonance occurs resulting in noticeable vibration. While the current tendency is to increase the rotation frequency of turbines, penstock plates are gradually becoming thinner. As a result of these trends, the occurrence of oval vibration has been reported at some hydraulic power stations. Since rules on vibration prevention do not always include oval vibration, we sought out detailed information on existing penstocks constructed within the last 30 years. Based on this information and a numerical study, formulae to calculate the natural frequencies of steel penstocks including those with circumferential stiffeners were proposed.

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