Seismic fragility of concrete box girder bridges in Malaysia

Abstract

In Malaysia, the majority of structures and infrastructures have not been designed for seismic actions. Recent earthquakes in the country, however, has raised the attention of authorities toward the seismic vulnerability of these structures. Bridges are among the crucial infrastructures that their functionality during ground motions is of great importance. In this study, three bridges with different pier heights of 10 m, 20 m, and 30 m were selected and their nonlinear response was determined through pushover and incremental dynamic analysis. By using 15 far-field earthquake records the seismic fragility curves of the bridges were derived. Peak ground acceleration was considered as the ground motion intensity measure and the drift ratio was selected as the engineering demand parameter. The obtained fragility curves revealed different patterns for the probability of exceeding light to severe damage for the studied bridges. While the difference between the probabilities of exceeding light and severe damage in the shortest bridge was significant, in the tallest bridge it was negligible. The bridge with the pier height of 20 m had the largest probability of exceeding light to severe damage when compared to other bridges. The tallest bridge, on the other hand, showed the lowest seismic vulnerability when compared with other bridges. Comparison between Malaysia national annex to Eurocode 8 and the obtained fragility curves revealed that for the estimated PGA in Kuala Lumpur, all studied bridges could remain functional.