Design estimates of surface wave interaction with compliant deepwater platforms

The extreme behavior of surface waves as they encounter and pass compliant deepwater platforms is an important class of problems for offshore engineer s attempting to specify the platform deck elevation. In this study analytic al expressions for the probability density and cumulative distribution func tions that utilize empirical coefficients in an attempt to accurately model surface wave runup and airgap problems are presented. The analysis focuses upon interpreting the tails of the measured data histograms using two para meter Weibull distribution models. The appropriate empirical constants, ass umed to be solely dependent upon the significant wave height, were evaluate d and compared for all the test data. Based upon a small select set of data , for a mini-TLP and two Spar platforms, the airgap problem was found to be adequately modeled using a Rayleigh distribution. Further, for the seven s eastates analyzed, the Weibull shape parameter was nearly constant and the data confirmed that the exclusive fit of the scale parameter assuming depen dence only on the significant wave height was a reason able approach for mo deling the wave runup. Finally, by combining these models with a Poisson re turn model for each storm the associated reliability estimates for various deck heights were estimated. (C) 2000 Elsevier Science Ltd. All rights rese rved.