Strong Ground Motion Characteristics on the Site with Irregular Topography and its Destructiveness for Structures.

1.通过对东北大学青山地区周边5个不同土壤条件和场地地形的观测，获得了许多地震动记录。研究了软土场地记录与岩石场地记录的谱比。这些光谱比平均显示出反映现场条件的特征形状，然而，它们也显示出相当大的散射。对入射波作用下沉积盆地边缘产生的面波振幅进行了解析研究。沉积物与基岩的横波速度对比越大，表面波振幅越大。盆地边缘的地形形状对表面波振幅的影响较小。入射波的入射角越大，表面波振幅越大。采用非线性有限元模型对神奈川县Ashigara山谷强地面运动进行了模拟分析。考虑土体非线性的最大加速度和地震动响应谱与实测地震动响应谱吻合较好。由于土壤的阻尼作用，河谷地形对地面运动的影响不显著。通过结构模型的弹塑性和弹塑性响应分析，研究了含有面波和体波的人工强地震动对结构的破坏作用。含有面波的地震动比只含有体波的地震动给结构带来更大的输入能量和响应延展性。

1.Many ground motion records have been obtained through observations on five sites with various soil conditions and site topographies around Aobayama area, Tohoku University. Spectral ratios of the records on the soft soil sites to the record on the rock site has been investigated. These spectral ratios show, on average, characteristic shapes reflecting the site conditions, however, they also show considerable scattering.2.Analytical study on the amplitude of surface waves generated at the edge of sedimental basin subjected to incident waves was performed. The larger contrast of S-wave velocity between the sediment and the bedrock gives the larger surface wave amplitude. The topographical shape of basin edge has less effect on the surface wave amplitude. The larger incident angle of incident wave gives the larger surface wave amplitude.3.A simulation analysis on the strong ground motion on the Ashigara valley in Kanagawa Prefecture, using a nonlinear finite element model, was performed. The maximum acceleration and the response spectrum of the predicted ground motion taking the nonlinearity of soil into account agree well with those of the observed ground motion. The topographical effect of the valley on the ground motion is not remarkable because of the damping effect of soil.4.Destructive effect to structures of artificial strong ground motion which contains surface waves as well as body waves was investigated through the elastic and elasto-plastic response analysis of structural models. The ground motion containing surface waves gives the larger input energy and response ductility to structures than the ground motion containing only body waves does.