| The reliability method, which can specify various influential factors in structural analysis, is more rational than the traditionally deterministic method. Structural reliability analysis approach has been successfully applied in many fields since 1960s. Currently, with the development of ship structural mechanics, reliability analysis approach used in ship structures is coming to be a hot research problem.With the object of reliability analysis for longitudinal ultimate strength of ship hull girder at the conceptual phase, this paper gives the effective methods respective for the determinations of the still water bending moment (SWBM), vertical wave bending moment (VWBM) and the ultimate longitudinal bending moment (ULBM) of ship hull girder according to their characteristics at this phase.The main research work and conclusions are summarized as follows:1. A semi-analytical approach is used to derive frequency response function and standard deviations for VWBM. The nonlinear effects of skewness and whipping are considered in this paper, and as the nonlinear moments are also expressed with semi-empirical closed-form expressions, it's very simple to estimate wave loads;2. Ferry-Borges method (FBC) is used to combine SWBM and VWBM according to their respective distribution characteristics;The distribution of each bending moment variable simulated by the type I extreme value distribution is discussed. And its mean and standard deviation are derived, which will be used in the following reliability analysis;3. According to the simplified progressive collapse analysis method based on Smith method, a simplified procedure is developed for predicting the ultimate longitudinal bending moment of the ship hull girder;4. Response surface method (RSM) for the reliability analyses of the ultimate longitudinal strength of ship hull girder is introduced, as the failure function can not be expressed definitely.
|
PDF Full Text Request