# Earthquake-Induced Pounding of Medium-to-High-Rise Base-Isolated Buildings
## 1 Introduction
A structural vibration control system composed of rubber bearing with magnetorheological damper was considered by [PERSON] et al. [24]. The results of the study indicate that the system is capable to reduce the structural response considerably, both at the superstructure and at the isolation level. Also, a new hybrid composite isolation system for the base of structures was proposed by [PERSON] and [PERSON] [25]. The system, based on the application of multi-layered laminated rubber bearing along with steel reinforcement, has been found to be effective in improving the seismic behavior of buildings. Considering the practical restrictions to the size of the seismic gap, the possibility of bounding of a seismically isolated building with adjacent structures during ground motions should be considered. The example of such a situation concerns the case of the Fire Command and Control base-isolated building that had been bounded with adjacent structures during the Northridge earthquake, causing the increase in the peak acceleration from 0.22 to 0.35 g (see [26]). Therefore, it is important to investigate the problem and understand how the maximum floor accelerations and inter-story deflections of seismically isolated buildings are affected by various design parameters and conditions during impacts with adjacent structures. Collisions in base-isolated buildings during seismic excitations may take place at the level of foundation (base), or at the story level in the case when structures are not sufficiently separated one from another. Most of the studies on earthquake-induced bounding in base-isolated buildings have been focused on collisions at the structural bases. [PERSON] [27] studied the response of an isolated building bumping against a rigid barrier using a shear beam model of the structure. Based on the results obtained, he underlined the extreme acceleration response due to collisions of the structure. The study on the effects of bounding between the base of an isolated building and the retaining wall was conducted by [PERSON] [28]. The results of investigation showed that the shear forces would be increased mainly due to the increase in the stiffness of superstructure or rigidity of retaining wall. [PERSON] [29] studied earthquake-induced collisions of a base-isolated structure which was modeled as a rigid block. [PERSON] and [PERSON] [30] evaluated the seismic performance of multi-story isolated building with the effect of bounding against the retaining wall. Bounding between the seismically isolated structure and the surrounding moat wall was also studied by [PERSON] et al. [31] and [PERSON] [32], so as to evaluate the influence of different design parameters and conditions on the peak accelerations and displacements. Further investigations were carried out for earthquake-induced bounding between different stories of two or three adjacent base-isolated buildings. [PERSON] et al. [33] considered the case of collisions between two-story structures. The analysis for few-story isolated and non-isolated buildings was also conducted by [PERSON] and [PERSON] [34], as well as by [PERSON] and [PERSON] [35]. The results of these studies show that bounding may considerably change the response of a base-isolated structure. The above literature review indicates that the research on earthquake-induced bounding of base-isolated buildings has been much advanced. However, the studies have been mainly focused on collisions between low structures, and the effects of bounding on such structures have been relatively well recognized (see [27; 28; 29; 30; 31; 32; 33; 34; 35]). Meanwhile, the number of medium-rise and high-rise buildings equipped with seismic isolation devices is growing rapidly. Therefore, the aim of the present paper is to investigate the influence of bounding on the response of medium-to-high-rise structures under different earthquake excitations. According to the authors' knowledge, such investigation has not been conducted so far.