Simplified Response Estimation Method of Buildings Due To Tsunami-Driven Ship Impact Loads

Abstract eng:
After the 2011 Great East Japan Earthquake, a joint team of the Institute of Industrial Science, The University of Tokyo (IIS UTokyo) and the Building Research Institute (BRI) conducted extensive damage investigations. Considering new findings learned from the investigation results, The Ministry of Land, Infrastructure, Transport and Tourism issued Interim Guidelines on the Structural Design of Tsunami Evacuation Buildings in November 2011. While massive waterborne debris such as ships can cause a critical global response of a building, impact loads due to the debris were not considered quantitatively in the guidelines. The authors, therefore, firstly defined an impact load due to a ship as a rectangular pulse based on the studies to evaluate the collision strength of a ship’s bow. Since the building response characteristics are significantly affected by the impact durations, the durations are then derived and compared to the natural period of a buildings. Secondly, the elastic building responses due to the impact loads are obtained by modal analyses and their characteristics are investigated. The maximum inter-story drifts below the impact-imposed floor level are generally found during the impact and are larger than those above the impact-imposed floor level. They are then simply estimated by the combination of the equivalent static inter-story drift and the first order mode drift. Finally, the accuracy of the proposed simplified estimation is verified parametrically to the impact durations. As a result, the estimated maximum inter-story drifts are found in a good agreement with those computed by modal analyses when the impact duration is longer than a half of the natural period of the building. Considering that the impact duration due to a ship can be generally longer than the natural period of a low- to medium-rise reinforced concrete building, the obtained equation is found widely applicable to estimate the maximum inter-story drifts of buildings due to the ship impact loads.

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