Evaluation of Tsunami Design Codes and Recommendations for Bridges Susceptible to Tsunami Inundation
Livermore, Spencer Nathaniel
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Much of the past tsunami research has focused on inundation modeling, evacuation strategies and to a lesser extent, building design. Although many of the bridges that lie within possible tsunami inundation zones provide critical lifelines to coastal communities, the effects of tsunamis on transportation systems have not been evaluated. The high fluid velocities, wave heights, long period waves and inundation speeds of tsunamis are not typically seen for storm surges or flooding, and result in large fluid forces on structures. As a result, design codes that consider storm surges and flooding do not reflect the extreme nature of tsunami loads. In this thesis the bridge types most susceptible to a large tsunami event along the west coast of the United States, as well as Alaska and Hawaii, are identified. Current tsunami loading methodologies are then summarized and compared. The extension of these methodologies to bridges is discussed, including research recommendations for fluid loading on bridge superstructures. The tsunami force equations were applied to two case studies. These studies provided the opportunity to evaluate the adequacy and varying approaches in estimating tsunami forces on bridge superstructures. In some cases the same tsunami force estimated by each of the codes and recommendations resulted in vastly differing forces. The influence of the estimate of flow parameters in some cases dominated the estimates. The discrepancies among the methods for estimating tsunami forces make the need for a unified tsunami design code apparent.
- Civil engineering