Evaluation of Tsunami Fluid Force Acting on a Bridge Deck Subjected to Breaker Bores

Abstract

The giant earthquake of MW=9.3 and the induced tsunami in December 26, 2004 caused the catastrophic damage of infrastructures. A bridge structure is an important infrastructure to support recovery activities after a tsunami event, hence it is required to keep the tsunami-proof capacity against the disaster. Therefore, evaluation of tsunami fluid force acting on a bridge deck, which is one of key structural components in a bridge structure, should be required in the design promptly. In this study, hydraulic experiments were carried out to clarify a tsunami wave load on a bridge deck, focusing on the effect of the type of breaker bores on the induced drag coefficient, and the variation of horizontal wave force effected by the changes of deck position from still water level against tsunami height. The averaged values CD of averaged drag coefficient were calculated as 1.52 subjected to surging breaker bores, and as 1.56 subjected to plunging breaker bores. The variation of horizontal wave force is more sensitive in the case that still water level is lower, and in the case that a bridge deck is subjected to plunging breaker bores. Previous proposed formulation associated with the computation of the lateral pressure on an engineered structure subjected to a tsunami wave is invalid for the evaluation of the lateral pressure on a bridge deck subjected to breaker bores.