Free field earthquake ground motions: effects of various numerical simulation approaches on soil-structure interaction results

Numerical analyses of dynamic soil-structure interaction treat small domains of interest, and employ special boundary conditions for accurately simulating the ground motions that occurred in the real site. The accuracy of the free field motion simulation is expected to have an effect on the response of the structural systems under consideration, and several approaches for such simulations have been proposed and used by various researchers. The present study was aimed to investigate the relationships between the type and accuracy of the free field input motion generation, and the resulting effects on the corresponding structures. Three types of free field simulations were employed for the analyses of three typical soil-structure configurations, and the results clearly show that the simulation accuracy is a critical factor in such studies. Furthermore, it is shown that some of the traditional methods for free field motion simulation in soil-structure interaction analyses may lead to significant underestimations of structural response levels, and anticipated system damage.