Review of existing literature on the topic of building pounding suggests that impact can not only result in potential structural damage, but can also result in large high frequency accelerations, that could cause malfunction of equipment installed within the buildings. The magnitude of impact effects caused by pounding is case-specific, and reliable methods to approximate impact effects are limited, due to the sensitivity of such predictions to both physical and numerical details. A rigorous analysis considering case-specific considerations is the preferred approach to investigate the effects of pounding with confidence.
In this study, the pounding caused by excessive seismic deformations of a fairly flexible structure to a relatively stiff concrete structure is investigated through a computational model. The type of structures investigated is representative of a typical design found in many power plants. The method used in the analysis couples interaction between two finite element structural models via a hybrid element in which nonlinear springs and dampers are activated during the approach period of impact. This process allows simulating the process of energy dissipation which takes place during the impact more accurately. Time history analysis is performed for various ground motions, and results are extracted in terms of impact force and acceleration response at various locations of the structures. The results from the detailed model are compared to a more simplified version of the model that represents the two buildings with single degree of freedom system, to evaluate the applicability of a simple model for use in initial screening assessment of the pounding effects. Additionally, the effect of uncertainties of local stiffness and damping of concrete in the impact zone are investigated to demonstrate the sensitivity of the results to variability of these parameters.
Based on the analyses performed, it is concluded that for this specific case study, pounding has negligible effects on the responses within the stiffer structure whereas it can have a pronounced effect on the response within the more flexible structure. More broadly, the case study provides a framework for assessing the effect of pounding that can be applied to other cases.