An experimentally validated approach for evaluating tsunami inundation forces on rectangular buildings

This paper presents an experimentally validated, closed-form set of equations for predicting forces on rectangular buildings impinged by nominally unsteady tsunami inundation flows. The shallow water waves that drive the tsunami inundation flows described in this paper are generated using a novel tsunami simulator, uniquely capable of generating very long period waves featuring the characteristic draw-down of real-world tsunami. We describe an experimental study of the forces acting on a rectangular building occupying 10-80% of a channel, fixed in a free-surface-channel flow driven by shallow water waves with periods of 20-240 s. An idealised topography and a 1:50 Froude scale are adopted. A one dimensional model based upon open-channel flow principles is proposed for unsteady flows driven by prototype tsunami waves, providing empirical estimates for drag and hydrostatic coefficients. It is observed that the pressure field around the buildings is hydrostatic irrespective of the flow being steady or unsteady. An empirically derived force prediction equation, dependent upon the Froude number of the incoming flow and blocking fraction is presented, which provides good agreement with the experimental results. The equations presented in this paper will provide engineers, tsunami modellers, and risk evaluation experts with a convenient method of tsunami inundation force determination without recourse to computationally expensive multi-scale numerical models.