MODIFIED MORISON EQUATION FOR DYNAMICALLY SENSITIVE PILE SUPPORTED WHARVES: DEVELOPMENT AND CALIBRATION USING CFD

Abstract

The Morison equation, developed in 1950, is used in engineering practice to calculate the lateral wave load applied to marine piles. It assumes a rigid pile response (i.e., it neglects the role of pile stiffness in impacting the dynamic response). This approximation may be reasonable when the ratio of wave load frequency to the piled wharf frequency is small but can yield considerable error when the ratio approaches unity (i.e., referred to as dynamically sensitive piled wharves herein). In this research, a modified Morison equation was formulated to consider the dynamic effect on piled wharves. The modified equation was calibrated using an extensive computational fluid dynamic (CFD) parametric analysis (360 simulation runs) and was based on principles of structural dynamics. The equation is presented in a user-friendly format and can be readily applied in engineering practice. It accounts for pile boundary conditions, pile stiffness, and wave characteristics. Practical examples of using the equation are provided for the design of piled wharves in Nova Scotia, Canada. Results indicate that the dynamic pile response is consistently observed to be greater for piles in shallow water compared to deep water when all other parameters are kept equivalent. The case study analysis results indicate that the original Morison equation can underestimate the lateral force on a piled wharf by approximately 15%, while it overpredicts the force in some scenarios by 10%.