Dynamic Soil-Structure Interaction Analysis for Structures with Flexible Foundation

• Main Authors: Chin-Long Wu, 吳金龍
• Other Authors: Der-Wen Chang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/31130566132212293505

碩士 === 淡江大學 === 土木工程學系碩士在職專班 === 92 === The effect of dynamic Soil-Structure Interaction (SSI) for structures with flexible foundation was studied. The sophisticated sub-structuring approach was employed for the subject analyses. Through numerical analyses of some examples for basic dynamic system, a general picture of the SSI effect was observed. Finally, some guidelines for engineering design were provided. The sub-structuring approach being utilized takes advantages of the rigorous frequency domain solution of the soil impedance and the versatile modeling capability of finite elements for the structure and soil. The input ground motion is expressed as a function of the free-field motion and the soil impedance in the formulation of the equation of motion. The free-field motion is obtained by solving 2D wave equation. The seismic-induced non-linear effects of soil are approximated by equivalent linear method. The solution of soil impedance is based on the hybrid modeling technique and complex response method. This analytical model is composed of finite element mesh of foundation soil, transmitting boundary, and viscous boundary. The case study was implemented for some basic dynamic systems with surface foundation. The parameter setting was such that the system’s fundamental periods covered the predominant periods of most earthquakes. In comparison with the corresponding fixed-base structures, the results of analyses revealed that the SSI effects would generally result in a reduction of dynamic response for most cases within engineering interest. In comparison with rigid foundation cases, the decrease of foundation’s stiffness would generally result in a reduction of dynamic response for the overall structure and significant influence to the adjacent members. However dynamic amplification effects were also observed for the cases with shallow soil stratum and some other cases. Therefore the design of rigid foundation is not necessarily beneficial for dynamic system, and the rigorous SSI analysis may be essential for engineering design.