Study on generation mechanism of vertical force peak values on T-girder attacked by tsunami bore

Abstract The generation mechanism and characteristics of peak values of tsunami bore vertical force are investigated comprehensively and thoroughly. A scaled down two-dimensional T-girder model, whose surface is divided into a series of panels, is tested in the cases with fixed initial downstream water depth, different incoming wave height and different initial clearance. Time history of vertical force is divided into four stages, in which the impinging stage is further divided into four sub-stages. Then the contribution rates of panels to the vertical force are discussed. Results show each peak value of vertical force in the impinging stage is composed of at least one peak value of vertical force on bottom panels of the girder, the continue increase of vertical force peak value is the result of more and more panels suffering static pressure of entrapped air when the chambers are successively closed by tsunami bore. The vertical force peak values on top panels of the chambers are mainly generated by the static pressure peak values of entrapped air. The entrapped air decreases the vertical velocity of tsunami bore under already closed chambers, resulting the simultaneous occurrences of pressure peaks of entrapped air in previous closed chambers.