MS7.2 - Dynamic Soil-Structure Interaction and Wave Propagation

Modelling of soil-structure interaction (SSI) problem has always been a challenging topic for structural engineers. In the last half-century, several simplified modelling techniques have been proposed to consider SSI by idealizing the soil domain. The behavior of these models are different in terms of complexity, accuracy and application cases. Thus, selecting a reasonably accurate and efficient model to simulate seismic soil-structure interaction is an important issue for structural engineers. The current study makes an attempt to assess the performance of three simplified modelling techniques (Gazetas spring and dashpots, Cone model and Beam on Nonlinear Winkler Foundation BNWF model) through a comparison study which is conducted on nine reinforced concrete Moment Resisting Frame MRF structures with various height and widths and two different soil profiles. The seismic responses of the structures are investigated through a nonlinear time history analysis and the performance of the models are compared in terms of capturing the period lengthening, lateral displacement, inter-story drift and total base shear in the structures. The strength, limitation and application cases of each model is also discussed. In addition, the influences of soil-structure interaction on seismic response of MRF structures on soft soil deposits are investigated and two main parameters (structure-to-soil stiffness ratio and structural slenderness ratio) are introduced which has shown great effects on controlling the role of SSI on building structures.

The Material Point method is a suitable numerical method to simulate large deformations that often occur in geotechnical engineering. The Double-Point MPM (2P-MPM) extends the simulations for water-saturated materials. In the present work, a coupled dynamic formulation is used to account for coupled wave propagation in porous media in addition to large deformations. The computational cost of 2P-MPM is expensive because information between material points and grid nodes must be approximated at each time step. In conventional 2P-MPM formulations, linear shape functions are used for this approximation, leading to well-known grid crossing and loss of contact problems. In our work, we present the moving least square approximation for the 2P-MPM to better handle these problems. In addition, a parallelization approach is shown to improve the computation time especially for large boundary value problems. The developed methods can be combined with non-saturated materials, such as fluids as well as dry soil, to simulate complex geotechnical problems. The performed computations of wave propagation as well as large deformations using the proposed methods show improved convergence behavior as well as increased efficiency.