ANSYS implementation of damping solvent stepwise extraction method for nonlinear seismic analysis of large 3-D structures

Abstract

A three-dimensional Damping Solvent Stepwise Extraction (DSSE) method is developed and implemented in the ANSYS finite element software for nonlinear seismic analysis of large-scale structures resting on an unbounded visco-elastic soil. Given a larger introduced artificial damping and arbitrary soil–structure interface geometry, the DSSE method provides a more efficient and accurate way to calculate the interaction forces of the unbounded soil within the framework of finite elements. In order to consider the effect of the artificial damping on structures, an Interface-Coupling element established with interface nodes in generalized structure substructure is developed through the element-based partition of the damped soil elements. The Newton–Raphson iteration method is employed along with the Newmark assumptions for the nonlinear analysis of generalized structures. The Newmark algorithm for damped bounded soil is also employed to assure the accuracy and convergence of the interaction system. User Programmable Features (UPFs) available in ANSYS is used to incorporate DSSE method. Also, a complete toolkit for general seismic soil–structure interaction (SSI) analysis is created using scripting-based ANSYS Parametric Design Language (APDL) and Graphical User Interface (GUI). The proposed technique is applicable to arbitrary sophisticated structure models, irregular soil domain, and provides the selection of the artificial damping without depending on the domain size of bounded soil. Two validation examples are presented to demonstrate the accuracy and efficiency of the proposed method. Moreover, an optimal case is suggested in view of engineering practice based on the comparison among the results from several sets of computational parameters including domain size, amount of artificial damping, and extraction steps. Nonlinear seismic analysis of high arch dam in south-west China is also presented to illustrate the analysis procedure, and demonstrate the capabilities of the method.