CORRECTION FACTORS FOR NONLINEAR RUNUP AND WAVE-FORCES ON A LARGE CYLINDER

A recently developed numerical method for second-order wave diffractio n is summarized and is used to develop a simplified approach to predic ting nonlinear runup and maximum wave loads for large coastal and offs hore structures subjected to regular waves. The perturbation method on which the method is based is extended to provide correction factors f or the runup and maximum loads. These correction factors apply directl y to the predictions of linear diffraction theory, and are independent of the wave height. The correction factors for runup, maximum force a nd maximum overturning moment are provided for a range of geometric pa rameters relating to the case of a large circular cylinder extending f rom the seabed to the free surface. Nonlinear runup and load maxima ca lculated by the correction factors are compared with the results of pr evious experimental studies; in general, favourable agreement is obtai ned. An example application of the proposed procedure is provided, the importance of nonlinear effects in the evaluation of runup and wave l oads is discussed, and the limitations of the results are indicated.