Performance of base‐isolated reinforced concrete buildings under bidirectional seismic excitation considering pounding with retaining walls including friction effects

Abstract

SUMMARY Seismic pounding of base‐isolated buildings has been mostly studied in the past assuming unidirectional excitation. Therefore, in this study, the effects of seismic pounding on the response of base‐isolated reinforced concrete buildings under bidirectional excitation are investigated. For this purpose, a three‐dimensional finite element model of a code‐compliant four‐story building is considered, where a newly developed contact element that accounts for friction and is capable of simulating pounding with retaining walls at the base, is used. Nonlinear behavior of the superstructure as well as the isolation system is considered. The performance of the building is evaluated separately for far‐fault non‐pulse‐like ground motions and near‐fault pulse‐like ground motions, which are weighted scaled to represent two levels of shaking viz. the design earthquake (DE) level and the risk‐targeted maximum considered earthquake (MCER) level. Nonlinear time‐history analyses are carried out considering lower bound as well as upper bound properties of isolators. The influence of separation distance between the building and the retaining walls at the base is also investigated. It is found that if pounding is avoided, the performance of the building is satisfactory in terms of limiting structural and nonstructural damage, under DE‐level motions and MCER‐level far‐fault motions, whereas unacceptably large demands are imposed by MCER‐level near‐fault motions. In the case of seismic pounding, MCER‐level near‐fault motions are found to be detrimental, where the effect of pounding is mostly concentrated at the first story. In addition, it is determined that considering unidirectional excitation instead of bidirectional excitation for MCER‐level near‐fault motions provides highly unconservative estimates of superstructure demands. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of Ground Motion Directionality on Seismic Response of Base-Isolated Buildings Considering Pounding to Adjacent Structures

“…A number of recent research works that extend the simulation in the more realistic 3D space [10][11][12][13][14][15][16][17][18][19] have been reported. Matsagar and Jangid [10] investigated the seismic response of a single-story asymmetric structure supported on various base-isolation systems during impact with adjacent structures.…”

“…The nonlinear viscoelastic model to assess the proper impact force during collisions had been incorporated on the 3D pounding between two adjacent fourand three-story buildings. The effects of seismic pounding on the structural performance of a base-isolated reinforced concrete building were investigated by Pant and Wijeyewickrema [15,16], aiming to evaluate the influence of adjacent structures and the separation between structures on the pounding response. Specifically, 3D finite element analyses of the baseisolated building were carried out considering various seismic excitations.…”

Failure of double friction pendulum bearings under pulse‐type motions

“…There has been significantly more study on the failure of rubber bearings than friction sliding bearings, and the shear failure and buckling failure behavior of rubber bearings is well understood . Researchers have even investigated the behavior of rubber‐isolated buildings in which large displacements cause pounding against the moat wall . However, there has been a minimal study on the failure of friction sliding bearings.…”

Damage‐based seismic planar pounding analysis of adjacent symmetric buildings considering inelastic structure–soil–structure interaction

“…Similar research was carried out on other base-isolated structures focusing on the acceleration response of floors [7]. The seismic behavior of pounding buildings was investigated by using lumped parameter gap elements [8,9]. In another work, it was reported that the period ratio of two adjacent structures determines the probability of occurrence of pounding [10].…”