Seismic analysis of mono-symmetric multi-storey buildings including foundation interaction

A method of analysis for the earthquake response of multi-storey mono-symmetric buidlings founded on flexible foundations is presented. The analysis also includes the sway (P-Δ) effects. The structural model considered herein is a linear N-storey building on a rigid footing resting on the surface of a linear elastic half-space. The system has 2N + 3 degrees of freedom. The governing equations are developed considering the motions of each floor and the whole system. In this method, first of all the structural deformations are obtained in terms of footing displacements using a linear combination of vibrational modes of the building on a rigid foundation which, in combination with the dynamic soil-structure interaction force-displacement relationships proposed by Veletsos and Verbic [J. Engng Mech. Div., ASCE 100, 189–201 (1974)] and Veletsos and Nair [J. Geotech. Engng Div., ASCE 100, 225–246 (1974)], result in integro-differential equations for footing displacements, which are then solved by numerical step-by-step time history analysis. A 10-storey building on soft soil was subjected to El Centro 1940 earthquake excitations in order to obtain the soil-structure interaction effects and the sway effects.