Non-Smooth Analysis of the Earthquake-Induced Pounding in Skew Bridges

Abstract eng:
Skew bridges with separation/expansion joints are one of the most common types of existing bridges worldwide. Earthquake reconnaissance reports indicate that skew bridges often rotate in the horizontal plane, increasing the chances of unseating at their acute corners. This behaviour is triggered by the oblique, in-deck, contact which leads in coupling of the longitudinal and the transverse response, binding in one of the obtuse corners and subsequently rotation in the horizontal plane, in such a way that the skew angle increases. Despite the recorded evidence from previous earthquakes, and most empirical vulnerability methodologies, which acknowledge skew as a primary vulnerability factor of bridges, the relevant literature lacks a thorough theoretical study and is mostly confined to empirical descriptions of the phenomenon. This study examines both the case of deck-abutment impact, as well as, the impact between adjacent deck segments, of skew bridges. It shows that the coupling, and hence the unseating during an earthquake excitation, after deck-abutment collisions is not a factor of the skew angle alone, but rather of the total geometry in plan plus the contact parameters. Finally, it offers closed-form solutions for all physically feasible post-impact states observed in skew bridges.

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