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In this study, a method for detecting the step and pulse components as well as estimating the displacement waveform based on seismic ground motion records was developed. These components represent the residual displacement and pulse-like ground motion in the near-fault region. In addition, the displacement waveforms were synthesized by combining the observed Fourier spectrum and obtained model spectrum instead of using a low-cut filter. Applying the proposed method to strong ground motion records during the mainshock of the 2016 Kumamoto earthquake, the displacement waveforms containing the step and pulse components were appropriately estimated.
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To verify the seismic performance of arch dams, it is necessary to evaluate the tensile stress caused by earthquake motion. When evaluating against strong earthquake motion, it is essential to consider the non-linearity of dynamic deformation property of dam. However, there is not much research on the effects of non-linear dynamic deformation property on seismic stress. The three-dimensional dynamic analysis was carried out to examine the impact on the seismic tensile stress when there is a reduction in dynamic shear modulus. The results show that both dynamic shear modulus and seismic tensile stress decreased at the most parts of the dam, but show an increase at the dam crest and abutment. In regard to seismic performance verification of arch dams, it should be noted that the seismic tensile stress may increase in some parts of dam by considering the non-linearity of dynamic shear modulus.
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Reliable estimation of surface fault displacements is necessary for the safety of infrastructure and buildings. It is essential to consider various uncertainties in the fault rupture process for the reliable estimation. In this study, the effect of material uncertainties on surface fault analysis was examined by performing ensemble simulations using Latin hypercube sampling. The convergence of probabilistic responses versus the number of samples was analyzed by computing multiple sample sets. It is shown that the critical value of the primary fault base slip at which surface faults appear on the ground are strongly affected by material uncertainties. The probabilistic distribution of the critical base slip can be approximated well by the log-normal distribution when the material properties are assumed to be log-normal random variables. The mean and standard deviation can be estimated with errors of several centimeters by conducting ten simulations when the material properties have coefficients of variance of less than 0.3.
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This paper describes a design method for tuned mass dampers (TMDs) that reduce seismic responses in reinforced concrete buildings. To reduce the seismic responses to a wide range of strong ground motions, displacement-dependent optimal tuning ratios of linear TMDs are formulated for nonlinear responses. Performance curve diagrams are proposed using the optimal tuning ratios determined by nonlinear time history analyses with various mass ratios and damping ratios. These diagrams allow us to visually determine the appropriate TMD under the constraints of its mass, damping coefficient, and peak deformation
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This study summarizes the predominant periods of the H/V spectral ratio of microtremors and sedimentary layer thicknesses above the engineering bedrock using topographic locations with varied landform evolution as objectives. The derived regression equation was unique to each location, indicating the evolution of the landform. Using the regression equation and earthquake observation data, we estimated the values of the ground’s predominant period, which were consistent with the actual measured values. This result confirmed the significance of topographic classification. When creating ground hazard maps, the hazard-prone area should be classified into topographic areas based on the landform evolution as the basic information for the zoning. Then, these topographic areas should be further classified based on the H/V spectral ratio of microtremors and sedimentary layer’s thickness.
