使用一維模式分析是否能在複雜的土層環境下模擬地表之受震反應並由此作為設計依據，至今多有疑問，因此本研究的目的在探討一維模式分析地表受震反應的適用性與合理性，以及側向非均勻土層在地表受震反應中所扮演的角色。本研究利用非線性二維有限元素法進行分析，其中土壤的非線性行為採用帽蓋模式來模擬。 由研究的結果發現，一維分析可以模擬彈性均勻土層的地表受震反應，但無法正確模擬彈塑性土壤受強震下之地表受震反應，亦無法反映側向非均勻土層對於地表受震的影響。當場址存在側向非均勻土層時，將嚴重影響地表受震的反應特性與大小程度。軟弱土層之雙側存在堅硬土層時，因軟弱土層內地震波能量集中，二維分析之結果大於一維分析，此時若以一維分析之結果作為設計的依據將嚴重低估地表受震反應。 It has long been recognized that site effect of the lateral heterogeneity of the ground can significantly affect the strong ground motion. In this study, a nonlinear two dimensional finite element model is adopted to investigate the effect of lateral inhomogeneity on the surface motion due to earthquakes. The nonlinearity of soil is assumed to follow the cap model. When the soil stratum is uniform and assumed to be elastic , the 1D analysis can predict the same response as 2D analysis , while it is not true for the nonlinear analysis . As for the case of soil stratum with lateral inhomogeneity , the 1D analysis will not be able to predict the response based on the 2D analysis . If a zone of weak soil is surrounded by a hard soil , due to the concentration of earthquake energy in the weak zone , the results obtained form 2D analysis are in general larger than those of 1D analysis , indicating that in such a case the case of 1D analysis will significantly underestimate the response of soil stratum .
