Experimental study of uplift pressures on wharf decks due to tsunami bores

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Cheng Chen, Bruce Melville

Wednesday 1 july 2015

8:30 - 8:45h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 8C. Coastal Engineering

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Tsunamis are extreme waves that can result from the sudden displacement of a significant volume of ocean water. Coastal buildings, bridges, highways, and harbour facilities that are at risk of tsunami inundation may suffer from significant damage if their structure has not been adequately designed for the fluid loading. This paper explores the behaviour of a combination structural model of a wharf deck mounted on a sloping shore and subjected to tsunami bores. The tsunami bores were generated in a tsunami wave flume and the deck model was built on a 30 degree sloping shore with a height of 25 cm above the bed. Detailed measurements of bore heights and bore velocities were recorded with depth transducers and high-speed video camera, and seven cases of hydrodynamic conditions were applied in the experiment. Pressure transducers were attached to the soffit of the deck to capture the spatial distribution of time-history of uplift pressures. Preliminary results demonstrate that the time-history of uplift pressures have three stages: impulsive, run-up, and quasi-steady. The impulsive pressures gradually reduced from the deck-slope connection to the front edge of the deck, and the impulsive pressures and run-up pressures appeared to be decreased by a side effect. Higher tsunami bores were generally found to generate higher uplift pressures, and a strong linear correlation was observed between the maximum uplift pressure and the bore height. An equation is presented for estimating deck mid-point maximum uplift pressures from bore heights, when the model bore heights range from 0.146~0.273m. Examples of applying the equation at prototype scales are given.