Seismic performance of base isolated buildings and strategies to mitigate vertical acceleration demands
Open Access
- Author:
- Vu, Bach Xuan
- Graduate Program:
- Civil Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 05, 2012
- Committee Members:
- Gordon Patrick Warn, Thesis Advisor/Co-Advisor
Swagata Banerjee Basu, Thesis Advisor/Co-Advisor
Ali M Memari, Thesis Advisor/Co-Advisor - Keywords:
- seismic
isolated
vertical
acceleration
mitigate
fragility
column isolators
elastomeric bearings - Abstract:
- Elastomeric bearing constructed of rubber layers bonded to intermediate steel shim plates is a seismic isolation device used for protecting a structure against earthquake ground shaking. The rubber layers provide the low lateral stiffness required to shift the period whereas the close spacing of the intermediate steel shim plates provides a vertical stiffness that is several thousand times larger than a horizontal stiffness. However, the low vertical isolation frequency can align with the dominant frequency content of the vertical spectrum leading to significant amplification of accelerations. An analytical study was conducted to investigate the influence of the vertical component of ground shaking on the performance of nonstructural systems within multi-story seismically isolated buildings. The research focuses on two dimensional analytical models of 3 and 9-story frames. Three model configurations are explored namely: frames with conventional base isolation, frames with base isolation and viscous dampers, and lastly frames with base isolation and column isolators. Fragility curves are used to assess damage to ceiling systems in both frames. Results from analytical analyses suggests that damage to ceiling systems might be mitigated in low-rise structure using moderate shape factor elastomeric bearings and supplemental damping, and in middle rise structure using high shape factor base bearings and column isolators.