Dynamic infinite elements for soil - structure interaction analysis

Abstract

In this dissertation, a method for the soil-structure interaction analysis incorporating infinite elements is presented. Axisymmetric dynamic infinite elements are developed for the efficient discretization of the far field region of the unbounded soil medium. The present infinite elements are capable of modeling of the multiple components of propagating waves. The shape functions of the infinite elements are formulated based on the approximate expressions for the analytical solutions of the propagating waves in the far field region. They are in terms of complex exonential functions associated with the corresponding wave numbers, which satisfy the Sommerfeld radiational condition. The number of wave components included in the shape functions can be increased by introducing nodeless variables. An efficient integration scheme is also devised for constructing the element characteristic matrices including multiple waves components. Numerical analysis results indicate that the present method incorporating the infinite elements yields very good results for the impedance functions of rigid circular footings on an elastic half space and also on layered half spaces. It is also found that the near field region may be maintained to be reasonably small. Hence computational efficiency can be achieved. The analyeses are also carried out for simulating the forced vibration test results and the earthquake response records by using the infinite elements. From the comparison with the experimental data, it is found that the present method utilizing the infinite elements is fairly applicable to predict the dynamic responses of soil-structure systems.