Design of Bridge Pier Pile Foundations for Ship Impact

Procedures to assess the equivalent static force acting on a bridge pier due to a vessel impact and various pier protective systems are briefly discussed. Equations and closed-form expressions are developed to obtain transverse and longitudinal components of ship impact, redistributed between pier and superstructure according to their relative stiffnesses. Plumb- and batter-pile combinations are compared. The necessity of investigating batter-pile combinations in several iteration cycles is stressed. Zero forces in "pulled-out" piles are assumed in each next consecutive iteration cycle until either stability or failure is reached. Battered piles increase axial forces but decrease bending moments. This reduction in flexure is important because it reduces significantly the required number of prestressing strands in the pile. As an illustration, a comparative plumb and batter pile foundation design of the channel pier of Howard Frankland bridge, in Florida, is given.