Comportement sismique des piles faiblement armées des ponts réguliers isolés à la base

Abstract

The main objective of this study is to assess the effect of lowering the minimum longitudinal reinforcement ratio in pier columns on the seismic performance and the behavior of baseisolated bridges. This study investigates the bidirectional behavior of a regular base-isolated bridge, with low longitudinal reinforcement ratios, under severe seismic loadings expected in eastern and western Canada. A typical two span bridge with a multi-column central pier and a precast superstructure is considered as a case study. 3D refined structural models of the isolated bridge were used where pier-columns were modelled by fiber elements to investigate the damage extent levels. Lead core elastomeric base isolators were considered and their shear behaviour was represented by a coupled bidirectional nonlinear hysteresis. Time history analyses were performed on the bridge models under simultaneous bidirectional components of seismic ground motion records as well as artificial seismic ground motions, scaled to Canadian Highway Bridge Design Code, the CSA-S6-14. In the first part of the study however, the seismic spectra of the NBCC2010 code edition was used given the unavailability of the NBCC2015 seismic spectra, used by the CSA-S6-14 code. Rectangular bridge columns with 0,3% to 1,0% of longitudinal reinforcement ratios were considered in the two parts of this study. Results focus on the effect of lowering the minimum longitudinal steel ratio on the damage extent and performance level described in the Canadian Highway Bridge Design Code CSA-S6-14 within columns critical sections. Results show that, Under the design earthquake, all the studied base-isolated bridge models, for all the studied reinforcement ratios, as long as they are not less than the required ratios, located in western and eastern sites, performed essentially within the elastic range that is according to the design philosophy of the CSA-S6-14 for lifeline bridges.

Date	4 Nov 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Amar Khaled (Supervisor) & Lotfi Guizani (Co-supervisor)