次結構法分析土壤-結構互制行為

Abstract

一般耐震工程設計均以剛性地盤進行分析，然而在過去許多案例皆顯示出土壤-結構之間的互制效應確實存在，此效應不但與土壤有關，亦受結構物動態特性、基礎幾何形式等諸多因素所影響，使得剛性地盤假設並不能完全適用於結構物受震反應時的分析。 因此，本研究以次結構法，推導出簡單的土壤-結構互制效應的分析模式。首先以有限元素軟體ABAQUS求出土壤-基礎的阻抗矩陣，繼而以模態分析法推導出上部次結構物的運動方程式後，與下部結構物於力平衡、位移一致下結合，得到土壤-結構互制效應的控制方程式並進行分析。 研究結果顯示，在考慮土壤-結構互制效應下，歷時反應較小，顯示出在某些情況下，以往的剛性地盤分析下，有過於高估其反應的情況，但並非所有的情況皆如此，端視結構物的週期、地震反應譜、土壤-基礎阻抗的大小而定。

For the analysis of structure subjected to seismic excitation, the foundations of the structure are usually assumed to be rigid. However, for some case this assumption may not be valid. Therefore, the paper is trying to derive a simple soil-structure interaction scheme by substructure technique, which can easily employ the existing commercial program. In this method, the soil-structure interaction problem is solving in frequency domain, since the impedance matrix for foundation is frequency dependent. To obtain the impedance matrix, the commercial program ABAQUS of finite element method is employed. Since using finite element method to solve the problem of wave propagation in half-space medium, one must pay attention to some precautions that are element size and domain size of finite element method. These effects will be investigated. After the equations of motion for soil-structure interaction analysis are derived and the impedance matrix is found. A numerical example of one seven-story building subjected to earthquake excitation is investigated in order to shed some light on soil-structure interaction effect on the responses of a building structure to seismic excitations.