Hybrid BEM-FEM for 2D and 3D dynamic soil-structure interaction considering arbitrary layered half-space and nonlinearities

Experiences and studies have shown that soil-structure interaction (SSI) effect has a vital role in the dynamic behaviour of a soil-structure system. Despite this, analyses involving dynamic SSI are still challenging for practicing engineers due to their complexity and accessibility. In this thesis, the hybrid BEM-FEM implementation is aimed at practicality by combining commercial software and an in-house code. The pre-processing task can be performed under one graphical environment, and it is enhanced with the capability to compute different types of dynamic sources and other improvements to increase its efficiency, accuracy, and modeling flexibility.  Further, the underlying soil is commonly a layered profile with arbitrary geometries. Most existing solutions solve the problem through simplification of the geometry and pattern. One of the main contributions in this thesis is the development of layer-wise condensation method to solve these cases using hybrid BEM-FEM. The method significantly reduces the computational memory requirement. Another challenge in the dynamic SSI addressed in this work is the consideration of secondary nonlinearities. Existing solutions using the time domain BEM and iterative hybrid method are computationally costly, and implementation of such a hybrid method on commercial software is tedious. The solution to address this case using a sequential frequency-time domain procedure is presented. The relatively simple approach makes it possible to consider the nonlinearities in the simulation without using the time domain BEM and without requiring additional iterations. Case studies demonstrating the application of the enhanced hybrid method are presented including cases of bridges, containment structures, and a 3D multi-storey structure under point source and double-couple sources. These case studies illustrate the role of following critical factors such as the site effect, inhomogeneity, and nonlinearities.




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