A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures

Ye Kun^1,2, Li Li^1,2 and Zhu Hongping^1,2

1. College of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan 430074, China
2. Hubei Key Laboratory of Control Structure, Huazhong University of Science and Technology, Wuhan 430074, China

Abstract: Base isolation can effectively reduce the seismic forces on a superstructure, particularly in low- to medium-rise
buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the base-
isolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with
adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this
paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple
pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the
potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the
modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference
between the numerical results from the various impact analytical models is not significant. Many numerical simulations of
BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and
floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the
ground fl oor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts
instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed
on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response
at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that
excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible
to pounding under a limited seismic gap.

Keywords: structural pounding; base-isolation; near-fault ground motions; Kelvin impact model; nonlinear damping
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