Author(s): Sungwon Shin; Mary Beth Oshnack; Daniel Cox; Chong Kun Pyun; Kyuhan Kim

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Abstract: Tsunami force and pressure distributions on a rigid wall were determined experimentally in a large scale wave flume. Forces were examined experimentally at three different cross-shore locations. Incident offshore and incident broken wave heights measured using wire resistance and ultrasonic wave gages. The force was measured using load cells. At each cross-shore location, the force showed an impulse peak followed by a period of sustained force. This type of profile was seen for each wave height tested. As wave height increased the maximum impulse force also increased. By comparing the force time histories with the integrated pressure distribution, it was also found that the hydrostatic pressure distribution accurately depicted the force profile during the period of sustained force. It was found that as the wall was moved further from the still water shoreline, the peaks were less pronounced and the corresponding maximum impulse force decreased. The sustained forces measured experimentally agreed well with the empirical formula for steady state force presented by Iizuka and Matsutomi (2000). This theoretical formula was also presented by both the FEMA Coastal Construction Manual (2000) and the City of Honolulu Building Code (2003) as the “hydrodynamic force.” Also, a modified COBRAS (COrnell BReaking wave And Structure) was employed and the results were compared with the data measured from the experiment. The impulse force on the wall was estimated by integrating the predicted pressure at each grid in the COBRAS result. The simulation results for impulse forces along the wall location were slightly underestimated compared with the data collected when the wall was located near the shoreline. However, the simulation results agreed well with experimental data as the wall move further from the shoreline.

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Year: 2012