The effects of the wave passage on the response of base-isolated buildings on rigid embedded foundations, 1993

In this report, the response in the frequency domain is studied for a building on rubber bearings subjected to incident plane P- and SV-waves and surface Rayleigh waves. A simple two dimensional soil-structure model is used, in which the building is represented by an equivalent single degree-of-freedom (SDOF) oscillator or a uniform shear beam, on a circular rigid foundation, which is embedded into a homogeneous elastic half-space. The soil-structure interaction is included. For simplicity, all the deformations are assumed to be in linear range. The response of this model is compared with the response of the commonly used fixed-base model.; It is concluded that, as a result of the soil-structure interaction, the relative building response is further reduced, but the overturing moment of the inertia forces of the building about its base is significantly larger, because of the larger rocking amplitudes of the foundation. Also, it is shown that, for incident waves for which the foundation input motion has considerable amount of rocking, relative to the amplitudes of the horizontal motion, the transfer function amplitudes of the relative building response are larger at the frequency of the second mode, than at the first mode. The opposite trend is noticed for isolated buildings on a rigid base.

本报告针对采用橡胶支座（rubber bearings）的建筑，开展其在入射平面P波、SV波与瑞利面波（Rayleigh waves）作用下的频域响应研究。本文采用简化的二维土-结构相互作用（Soil-Structure Interaction）模型：将建筑等效为单自由度（SDOF）振子或均匀剪切梁，设置于圆形刚性基础之上，该基础埋置于均匀弹性半空间中，且考虑了土-结构相互作用效应。为简化分析，假定所有变形均处于线性范围内。将该模型的响应与常用固定基础模型（fixed-base model）的响应进行对比。研究结果表明，由于土-结构相互作用的影响，建筑的相对响应有所降低，但因基础摇摆幅值更大，建筑底部惯性力产生的倾覆力矩显著增大。此外，研究还发现：当入射波使得基础输入运动中，摇摆分量的幅值相较于水平运动幅值较为显著时，建筑相对响应的传递函数幅值在二阶振型频率处大于一阶振型频率处；而对于刚性基础上的隔震建筑（isolated buildings），该趋势恰好相反。