本研究探討群樁基礎橋梁受沖刷與地震之複合式災害作用下之受震反應。規劃單柱式橋墩與群樁基礎裸露橋梁模型，並使用大型雙軸向多層剪力試驗盒模擬半無限域之土層，進行振動台試驗以獲取樁基礎橋柱模型於不同裸露深度之動力反應。

茲對群樁基礎橋柱模型進行系統識別，掌握模型之相關動力特性。試驗結果顯示，本試驗模型中土壤貢獻了絕大部分的阻尼比，而隨著裸露深度加深，試體基本振動週期隨之延長，但系統阻尼比無顯著變化；而於地震歷時中，試體基本振動週期與阻尼比會隨著地震歷時前段地表振動劇烈時而提升，而當地表振動緩和時試體基本振動週期與阻尼比下降。

試驗結果顯示裸露深度增加，基樁最大彎矩值隨之上升，且彎矩位置分布亦會改變；而橋柱彎矩可能會於裸露至特定深度後下降。

數值分析方面土壤-結構互制行為係採用非線性土壤彈簧(p-y curves)模擬，並建立三種不同方式之數值模型進行模擬。分別為使用SAP2000蒐羅國內相關公式行土壤-結構互制行為之模擬、SAP2000利用API公式進行土壤-結構互制行為之模擬，與使用OpenSees建立存在彈性、塑性、間隙之土壤彈簧模型之模擬，以探討其適用性、差異性。研究結果顯示，使用SAP2000利用API公式進行土壤-結構互制行為之模擬與使用OpenSees建立存在彈性、塑性、間隙之土壤彈簧模型之模擬皆有不錯之分析結果。

In this study, the impact of scouring on the seismic performance of bridge pier with pile-group foundation was investigated under multi-hazard circumstances. The model bridge pier with pile-group foundation comprised a lumped mass, a steel pier, and a footing supported by a aluminum group pile within dry soil. The shaking table test was carried out to study the dynamic response of the bridge pier with pile- group foundation model at different bare depths.
Conducting dynamic system identification to the bridge pier with pile- group foundation model to realize dynamic characteristics. The test results show that the soil contribute most of the damping ratio. As the exposure depth deepens, the basic vibration period of the specimen is prolonged, but the system damping ratio didn’t change significantly. During the time history, the basic vibration period and damping ratio of the model would increase in the ground motion with high acceleration. When the ground motion is moderated, the basic vibration period and damping ratio of the model will decrease.
As the exposure depth deepens, the maximum bending moment of the pile increases and the position distribution of the bending moment changes. The maximum bending moment of the bridge piers may decrease after exposure to a certain depth.
Soil-structure interaction behavior is simulated by nonlinear soil spring (p-y curves) and establishes three different numerical models for simulation. The first way is the simulation of soil-structure interaction behavior using relevant domestic research formula, which is modeled by SAP2000. The second way is the simulation of soil-structure interaction behavior using API formula, which is modeled by SAP2000. The third way is the simulation of soil-structure interaction behavior using soil spring with elastic, plasticity and gapping behavior, which is modeled by OpenSees.
The results show that simulation of soil-structure interaction behavior using API formula modeled by SAP2000 and simulation of soil-structure interaction behavior using soil spring with elastic, plasticity and gapping behavior modeled by OpenSees can effectively predict the behavior of the test model.

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