[[alternative]]Seismic Response Analysis for Simplified Bridge Structure Including Pile Foundation

[[abstract]]橋梁結構的地震反應經常使用2維或3維有限元素法進行分析，然是項分析相對複雜，輸入檔龐大、準備不易；若將其下之基礎和地盤柔度一併納入分析，則尚須考慮土壤材料組構行為、網格切割、分析域範圍和邊界條件等影響因素，諸項細節均使得上述分析不易成為橋梁基礎耐震設計之例行檢核項目。為此，本研究乃建議一簡易之橋墩結構和樁基礎的地震反應分析法，首將地盤和橋墩基礎拆解成獨立之子結構系統、利用集中質塊分析法求出自由場受震反應，後將地盤運動植入樁基之波動方程數值解以計算基樁反應；上部橋梁結構可化簡為雙自由度質塊系統，藉先前之基礎反應推算上部結構位移，再藉上部結構和基礎間之傳遞力反覆求解結構系統之力平衡性。該項分析與有限元素法比較證明可行，可大幅減少分析時間，同時方法易於明瞭，適於大地工程之設計實務應用。[[abstract]]Seismic responses of the bridge structures are often obtained from 2D or 3D FEM analyses. These analyses are relatively complicated, and the preparation of considerable amount of input data is quite difficult. For problems considering soil-structure interactions, the analysis requires further carefulness for the soil model, discrete mesh and core dimensions as well as the boundary conditions. All the details have made the FE method the exclusion for routine examination work on seismic design of the bridge foundation. Owing to this concern, this paper suggests a relatively simple approach for dynamic analysis of the bridge-pier-pile structural systems. In this method, the ground and foundation are decomposed into substructures whereas the free-field response is first obtained from the lumped mass analysis. The corresponding pile movements are then computed from the discrete wave equations. Assuming a two-degree-of-freedom system for the superstructure, the correspondent bridge motions can be modeled from the seismic excitations of the based piles. Force equilibrium between these substructures needs further verification to ensure that it is satisfied. This analysis is validated with the FEM solutions. It reduces a great deal of computation time, and it is much easier for engineers to understand, and is to be appropriate for routine geotechnical engineering design.[[sponsorship]]淡江大學土木工程學; 系三力工程顧問; 介興營造[[conferencetype]]國內[[conferencetkucampus]]淡水校園[[conferencedate]]20050908~20050910[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]臺北縣, 臺