The effect of soil structure interaction on structural seismic demand: Neglected or considered?

Abstract

Construction industry has advanced significantly in terms of size and type in recent years in Albania. However, the design is generally based on a fixed based structural model,and the dynamic soil-structure interaction is often neglected even for soft soils. Investigating the seismic demand including soil-structure interaction (SSI) effects is a relatively difficult task due to the complexity of the coupled dynamic problem: uncertainty of the soil and structure parameters and the inherent randomness of the earthquake ground motion.The main objective of this paper is to focus on the SSI effects on the seismic demand.This goal is accomplished through studying an eight storey building frame in conjunctionwith two different soil deposits: stiff soil with shear wave velocity approximately 600 m/s;and soft soil with shear wave velocity less than 180m/s. The frame is modelled and analyze dunder two different boundary conditions: Fixed-based assuming the foundation is completely rigid; and considering the soil-structure interaction, modelling the soil-structure system as a mass with springs at the base.A response spectrum analysis is performed and the results of the structural models are compared in terms of natural period, vibration shape modes, structural displacement, inter story drift and internal forces and moments.