Experimental study of uplift loads due to tsunami bore impact on a wharf model

Abstract

Tsunamis are unpredictable disasters that have occurred frequently in recent years. An experimental study was conducted to quantify the tsunami bore uplift loads on a deck mounted on a slope, representing a typical wharf structure. Tsunami bores were generated as dam break waves in a flume, and the bore Froude number was approximately 1.6 on the dry bed. Fifty-five tests (11 bore cases, 5 runs each cases) were conducted for detailed measurements of bore height and bore velocity, and 504 tests (7 bore cases, 3 deck heights, 8 wharf slope angles, 3 runs each combination) were conducted for measurements of time-histories of pressure on the soffit of the deck. The effects of bore height, deck height and slope angle on uplift loads were studied. Results show that bore height correlates with bore velocity. The flow motion of the tsunami bore impacting the deck is divided into five stages: front-climbing, front-hitting, run-up, quasi-steady, and recession. The uplift pressure decreases from the deck-slope connection to the deck front edge, and the total uplift load increases with increasing bore height or decreasing deck height. For the front-hitting stage (the maximum pressure), the uplift load increases as the wharf slope angle decreases. However, for the quasi-steady stage (the longest time period), the uplift load is consistent for different wharf slope angles. Based on the experimental data, the equations for predicting the front-hitting and quasi-steady pressures are proposed as functions of bore height, deck height and wharf slope angle, and the predicted values are within ±20% error.