A WINKLER MODEL FOR THE SEISMIC ANALYSIS OF STRUCTURES ON CAISSON FOUNDATIONS

An analytical model for the analysis of the dynamic behaviour of caissons foundations is presented. The model is based on the Winkler’s assumption and permits the evaluation of the impedance functions and the foundation input motion that can be used, in the spirit of the substructure approach, to perform seismic soil-structure interaction analysis of structures on caisson foundations. Stress resultants in the foundation due to the propagation of seismic shear waves in the soil can be also estimated. A Timoshenko beam model is considered for the caisson and the interaction forces with the soil are obtained by studying the plane-strain vibration problem of an annular rigid ring into the soil. The problem is formulated in the frequency domain and the solution is obtained exploiting the finite element approach. The model validation is obtained by comparing results with those achieved with more rigorous BEM-FEM models of the soil-caissons systems. The model, which is characterised by a very low computational effort, revealed effective in capturing the dynamic response of caisson foundations predicted with more rigorous methods.