Direct modelling of dynamic soi-structure interaction by finite elements analysis

The objective of this paper is to investigate the impact of different types of artificial boundaries on the dynamic behaviour of a free oscillating structure founded at the surface of a soil deposit. The superstructure consists of a moment resisting frame and the soil is considered as a stress dependent medium. 24 DSSI 2D finite elements models are constructed on OpenSees platform. Beam-column elements with fibre sections, including confined and unconfined concrete and steel reinforcement, are employed to represent the frame members. Soil behaviour is modelled using an inelastic multi-yield surface material to a depth of 30 meter in total stress condition. Three different types of lateral boundaries are applied to the soil domain in order to assess their impact on the period elongation and overall damping of the structure under free vibration. Different soil width-to-depth ratios ( =w/H) are considered to evaluate the influence of the distance between the lateral boundaries and the structure. The study showed that the best approach to model the artificial lateral frontier for the problem of the free vibration of a structure located at the surface of an inelastic soil domain (depth 30 meter modelled as a stress dependant medium) is the viscous lateral boundary, using large lateral distance between the structure’s footing and the lateral boundary (w ≥ 8.