Direct-Iterative Hybrid Solution in Nonlinear Dynamic Structural Analysis

Although many advanced sparse direct solvers are widely used in structural analysis, these often require longer computing times than iterative solvers for well‐conditioned structural systems. However, iterative solvers cannot efficiently solve an ill‐conditioned system when a structure becomes highly nonlinear. This work proposes a hybrid solution integrating a direct solver and an iterative solver to reduce overall computing time in solving a series of linear equations arising from nonlinear dynamic structural analysis. The hybrid solution selects the iterative solver, which reuses the factorized matrices for preconditioning, and switches to the direct solver in the initial stage or when factorized matrices need updating. The performance of the hybrid solution is tested on the OpenSees platform. The results show that the hybrid solution outperforms the direct solver, even when the structure becomes highly nonlinear during analysis.