Response of seismically isolated buildings considering poundings

Abstract

Numerical simulations and parametric studies have been used to investigate the influence of potential poundings of seismically isolated buildings with adjacent structures on the effectiveness of seismic isolation. Poundings are assumed to occur at the isolation level between the seismically isolated building and the surrounding moat wall. After assessing some common force-based impact models, a variation of the linear viscoelastic impact model is proposed to avoid tensile impact forces during detachment, while enabling the consideration of permanent plastic deformations at the vicinity of the impact. A large number of numerical simulations of seismically isolated buildings with different characteristics have been conducted under six earthquake excitations in order to investigate the influence of various design parameters and conditions on the peak floor accelerations and interstorey deflections during poundings. The numerical simulations demonstrate that poundings may substantially increase floor accelerations, especially at the base floor where impacts occur. Higher modes of vibration are excided during poundings, increasing the interstorey deflections, instead of retaining an almost rigid-body motion of the superstructure, which is aimed with seismic isolation. Impact stiffness seems to affect significantly the acceleration response at the isolation level, while the displacement response is more insensitive to the variation of the impact stiffness. Finally, the results indicate that providing excessive flexibility at the isolation system to minimize the floor accelerations may lead to a building vulnerable to poundings, if the available seismic gap is limited.

An Efficient Numerical Approach for the Parametric Investigation of the Effects of Pounding on the 3d Dynamic Response of Buildings During Earthquakes

“…the impact stiffness and impact damping coefficients is a common difficulty when using forced-based impact models and it is often considered one of the major disadvantages of this method. Nevertheless, several numerical studies in 2D showed that in the case of simulating the problem of earthquake induced pounding of adjacent buildings, the values of the impact parameters slightly affect the overall structural response, besides of the acceleration at the impacting floor [9]. In the frames of the current study, a simple approximation is followed in order to determine a reasonable value for the impact stiffness and impact damping in both normal and tangential directions of the contact plane.…”

“…The results from the various 2D parametric studies have demonstrated the detrimental effects of pounding on the dynamic response of multistory buildings and showed the importance of this problem regarding the safety and functionality of these structures. Studies have also revealed the consequences of structural pounding on the dynamic response of seismically isolated buildings, which exhibit quite different dynamic characteristics from fixed-supported buildings [9][10][11]. Actually in the case of seismically isolated buildings the problem of the amplification of the response due to pounding is considered to be more serious since it is more likely to have more demanding performance requirements and higher expectations than for conventionally fixed-supported buildings.…”

Prediction of Critical Distance Between Two MDOF Systems Subjected to Seismic Excitation in Terms of Artificial Neural Networks

“…An experimental test by using different balls was carried out by Jankowski et al [13,14] and shown the effect of body material to impact velocity. Komodromos [15], Ye et al [16] and Yu and Gonzalez [17], Naderpour et al [18] have mathematically described various equations to determine impact damping ratio.…”

Suggestion of an equation of motion to calculate the damping ratio during earthquake based on a cyclic procedure

“…They coordinated a stereo-mechanical model with energy loss during the impact. Komodromos et al (2007) expressed an equation of motion to create an impact between two bodies, which could estimate the impact damping ratio. The base isolation systems have recently been described by Polycarpou (2011, 2012) and the pounding was numerically investigated.…”