Using seismic restrainers with gap to reduce isolator displacements in seismic-isolated bridges subjected to pulse-type ground motions


DİCLELİ M., Kurtman B.

10th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2020, Sapporo, Japan, 11 - 15 April 2021, pp.3996-4001 identifier

  • Publication Type: Conference Paper / Full Text
  • Doi Number: 10.1201/9780429279119-547
  • City: Sapporo
  • Country: Japan
  • Page Numbers: pp.3996-4001
  • Middle East Technical University Affiliated: Yes

Abstract

© 2021 Taylor & Francis Group, LondonFor seismic isolated bridges (SIBs) subjected to near-fault (NF) ground motions with directivity effect, the isolator displacements tend to be considerably large. Consequently, isolators with very large dimensions may be required for SIBs located in NF zones. This may lead to very large expansion joints and very large seat widths as well. In this research, the efficiency of providing supplemental elastic-gap devices to improve the performance of seismic-isolated bridges (SIBs) in near-fault (NF) zones is investigated. The device is primarily made of elastomeric bearings placed in parallel with seismic isolators to provide additional elastic stiffness upon closure of a gap. A parametric study, involving more than 400 nonlinear time history (NLTH) analyses of realistic and simplified structural models of typical SIBs are conducted using simulated and actual NF ground motions to investigate the applicability of the proposed solution. It is found that providing elastic-gap device is beneficial in reducing the isolator displacements to manageable ranges. It is also found that the gap and the stiffness of the elastic-gap device may be chosen in relation to the magnitude of the NF ground motion to minimize the isolator displacements by avoiding resonant response. Further analyses conducted using a realistic structural model of an existing bridge and five NF earthquakes with moderate to large magnitudes confirmed that elastic-gap device may be used to reduce the displacement of the isolators while keeping the substructure base shear forces at reasonable ranges for SIBs located in NF zones.