Seismic Analysis of Beams on Two-Parameter Foundations

Abstract

Seismic behavior of an inelastic beam resting on a nonlinear soil bed is analyzed with the development of fiber beam element. The Winkler approach models the soil as a single layer, and assumes that the foundation reaction at a particular point is proportional to the soil displacement. In this paper a new finite element formulation was developed to simulate the seismic performance in which the soil can be viewed as a semi-infinite inelastic element that can resist bending, in addition to the well-known Winkler effect. The non linear response of structures resting on this improved foundation model is analyzed following a Vlasov approach with soil parameters based on a plane strain assumption. The tensionless character of the foundation results in the creation of lift-offs between the beam and foundation is also being considered. Effect of the earthquake intensity on drift demands is investigated. Parametric analysis of the reinforced concrete and steel foundation elements are carried out and comparisons were made with the simple Winkler model. The presented solutions and applications show the superiority of the element in simulating the seismic response of foundation structures.