The safety of coastal infrastructure has been a concern after the Indian Ocean Tsunami in 2004 and the Great East Japan Tsunami in 2011. The western coast of the United States is also exposed to tsunami hazards due to the Cascadia subduction zone. Therefore, it is critical to design coastal infrastructure, bridges and buildings in particular, for tsunami loading. After a tsunami event, coastal bridges are critical to the transportation in securing the evacuation of people, sending equipment to destroyed area, and reconstructing essential facilities. However, general loading equations to design bridges are not available. Although loading equations for buildings are available, current research on tsunami loading on buildings is based on the assumption that buildings are rigid.
To refine tsunami loading equations and investigate mitigation strategies, it is necessary to use numerical simulation in addition to experiments. An all-encompassing source-to-bridge simulation to determine bridge forces is not realistic due to the different scales between ocean shallow wave flow and localized bridge geometry. Thus, it is desirable to have an efficient approach to impart a wave of given height and velocity on a bridge model.
In this research, a simplified numerical tsunami bore is proposed and validated. In order to provide enough samples to generate loading equations, the simplified bore is used to test bridge scenarios with different wave heights, bridge to standing water level (SWL) clearance and bridge configuration. In turn, loading equations on bridges are proposed with empirical coefficients. Good prediction of the tsunami loading equations to numerical bridge simulations is observed. Other factors that affect the tsunami loading on bridges such as superelevation, rail, and inclined surface of the bridge are considered as extra coefficients applied to the loading equations.
To further examine the role of structural flexibility, a two-story flexible building model is tested with different inundation height and imparted with broken solitary waves while inundated in the OSU wave flume laboratory. It is found that as the inundation height increases, the fundamental period and damping ratio of the structure increases.