Design Equation for Wave-Induced Uplift Forces on Elevated Structures

This paper introduces a conservative design equation for wave-induced uplift forces on an elevated structure. The equation is an extension of previously developed design equations to estimate the horizontal wave–induced pressure distribution on an elevated structure. The uplift equation relates the pressure at the lowest element on the face of the structure to the pressure at the leading edge on the bottom of the structure via an empirical uplift coefficient, Cu. The uplift coefficient was determined experimentally from a large (1:10) scale experimental dataset of random wave pressures and forces on an elevated specimen. The pressure distribution along the bottom of the elevated structure was assumed to be triangular, with zero pressure at the trailing edge. The proposed design equation was shown to be conservative in predicting large vertical forces (F1/250) with safety factors (SF) between 0.96 and 3.08 and characteristic vertical forces (F1/3) with a mean SF of 5.06 across a range of significant wave heights, peak wave periods, and air gaps. The proposed equation can be considered more applicable for engineering design compared with existing equations for vertical uplift, which are shown to be either unconservative (SF < 1.0) or highly conservative (SF > 10.0) in predicting wave-induced uplift forces.