近年地震對世界各地造成之重大災害，使隔震系統成為位於地震帶國家經常使用之耐震設計方式，藉由延長結構物自然振動週期，以降低引致之地震力，其效益更勝於傳統採用韌性設計之耐震系統。過去已有多位學者提出橋梁直接基礎搖擺機制如同隔震系統，並於震後發現直接基礎之搖擺機制可降低傳遞至上部結構之地震力，並且透過搖擺機制產生振動周期延長降低地震力，也可藉由土壤於大地震下之塑性行為吸收地震能量。 本研究旨在將已開發非線性土壤元素放入空間向量式有限元素計算流程中，建立土壤與基礎互制之模型驗證彈簧之正確性，並模擬橋梁於強震中土壤與基礎之高度非線性行為。 本研究採用空間向量式有限元素(3D Vector Form Intrinsic Finite Element)為結構動力分析方法，此方法適用於處理大變形、大變位、材料非線性與剛體運動等問題。為了模擬土壤與基礎互制關係，本研究參考UC Berkeley團隊非線性土壤彈簧模型(Beam-on-Nonlinear-Winkler Foundation)，此模型可用以模擬垂直向土壤(q-z spring)、水平雙向被動土壤(p-x & p-y spring)與土壤結構間摩擦力(t-x & t-y spring)，經由算例分析驗證此土壤彈簧之正確性，最後以五跨連續梁橋作為模型，探討其參數變化對橋梁之影響，並模擬至極限狀態，瞭解橋梁在在極限狀態下之橋梁反應。 ;In recent years, the earthquake caused many disasters in the world. Many countries must be use the isolation system in seismic design. By prolonging the structural period to reduce the seismic force is better than traditional design. From researches we can see that the rocking response of spread foundation is a unique isolation system. After earthquakes, the rocking mechanism of spread foundation can reduce the seismic force of the main structure, besides it can extend the period of structure and decrease the seismic force. In addition, the soil will generate the plastic behavior and absorb the seismic energy under the extreme earthquake. This study aims to place the nonlinear soil spring to the 3D-VFIFE calculation process. Modeling soil and foundation interaction system to verify the correctness of the nonlinear soil spring, and simulate the bridge’s extreme behavior in the earthquake. 3D Vector Form Intrinsic Finite Element, a new computational method is adopted in this study because the VFIFE has the superior in managing the engineering problems with material nonlinearity, discontinuity, large deformation and arbitrary rigid body motions of deformable bodies. In order to simulate the interaction between soil and foundation, the study reference UC Berkeley team’s soil spring (Beam-on-Nonlinear-Winkler Foundation). This model can simulate the vertical soil (q-z spring), lateral passive soil (p-x & p-y spring) and the friction force between soil and foundation (t-x & t-y spring). Through numerical simulation of examples to verify the soil element model are feasible and accurate. Finally, five-span continuous bridge as a model to investigate the effect of the parameter changes, and to understand the bridge behavior in ultimate condition.
