Effet des séismes bidirectionnels sur la longueur d'appui des tabliers de ponts

Abstract

The loss of support has been identified as one of the main causes of bridge collapse during past earthquakes. To avoid this problem during future major seismic events, modern North American bridge design codes and regulations require providing a minimum support length at expansion bearings to accommodate bridge deck displacements. The empirical support length, N, required by the CSA-S6 Canadian highway bridge design code has been developed by the AASHTO based on ground motion earthquakes anticipated in Western American coast regions of high seismic hazard. A study has been conducted to examine the effect of bidirectional ground motion earthquakes on the longitudinal bridge deck displacement and the effectiveness of the empirical support length, N, for bridge structures located in eastern Canadian regions of moderate seismic hazard. The study consists in a series of time-history analyses performed on 15 regular and irregular bridge models, typical of those encountered in the eastern Canadian highways. A set of five pairs of recorded historical ground motion earthquakes were used in this study. The maximum seismic longitudinal bridge deck displacement, for each model was computed: (a)using the ground motion earthquake component separately in each principal direction of the bridge models, and (b) using simultaneously the pairs of orthogonal seismic ground motions. The values of the bridge deck maximum seismic displacements computed using time-history analysis show that the minimum support length, N, required at expansion bearings by the CSA-S6 code is too conservative for Eastern Canadian regions of moderate seismic hazard. The results also show that bridges with skew angle not more than 30° need not be analyzed for bidirectional ground motion earthquakes. However, the effect of bidirectional ground motion earthquake should be taken into account in the case of bridges with a skew angle greater than 30°.

Date	26 Feb 2014
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Amar Khaled (Supervisor) & Marie-José Nollet (Co-supervisor)