NUMERICAL STUDY OF THE SOIL-STRUCTURE INTERACTION DURINGSTRONG EARTHQUAKES

摘要

The non linear dynamic soil-structure interaction of three reinforcement concrete building frames (3, 6,and 12 levels) subjected to strong earthquakes is studied using the FEM. The soil behaviour is modelledwith hypoplastic and visco-hypoplastic relations which are able to model the response of cohesionless andcohesive soils under alternating and dynamic loading, for drained and undrained conditions. The behaviourof reinforced concrete is modelled using an elastic-plastic constitutive law for the plain concrete andelastic-ideal plastic for the steel bars. It is assumed that the buildings are founded on a layered groundfrom Treasure Island, San Francisco Bay (Seed et al., 1991). An acceleration record at Yerba Buena Islandduring the Loma Prieta 1989 earthquake is used as bedrock excitation. In order to quantify the influence ofthe soil-structure interaction, the ground motion at the foundation depth due to the bedrock excitation isfirst calculated without considering the structure ('free field acceleration'). This ground motion is thenapplied to the base of the buildings to evaluate the internal forces and deflections of the structure. In athird analysis, the dynamic response of both structure and soil due to the same bedrock excitation is considered.Based on the comparison of the numerical results it is concluded that the proposed numericalmodel is a powerful tool to quantify the influence of soil-structure interaction on the response of buildingsduring strong earthquakes.