An Application of Design Load Generator to Predict Extreme Dynamic Bending Moments

Two important components of dynamic bending are wave-induced bending and impact-induced whipping. Traditionally, dynamic loading has been incorporated into design load estimations via rule-based design approaches, most of which are inherently empirical. However, rule-based approaches may not guarantee a robust design in an unconventional system where experience is limited or operational requirements are rather special. To address this limitation, a Design Load Generator (DLG) is applied to construct an ensemble of short input time series that will return target extreme events at a preset time. To calculate the target extreme events, the DLG utilizes optimized non-uniform Fourier phase distributions. For nonlinear simulations, the current DLG requires an additional nonlinear simulator. To account for the nonlinearity associated with the dynamics of ship motion and to calculate the whipping response due to hull bottom slamming, the Large Amplitude Motion Program (LAMP) developed by Science Applications International Corporation (SAIC) is used. A Joint High Speed Sealift (JHSS) concept of the U.S. Navy is chosen to illustrate the current DLG methodology. The target extreme midship bending moments from the DLG are compared with the results from a short-term Monte Carlo simulation in the Weibull space to demonstrate the potential of the methodology.