RELIABILITY AND UNCERTAINTY EVALUATION FOR LONGITUDINAL BENDING OF HULL GIRDERS OF SURFACE SHIPS

Structural reliability and uncertainty assessment of hull-girder bendi ng of surface ships requires the consideration of the following three aspects: (1) structural strength, (2) loads, and (3) methods of reliab ility analysis. A methodology was developed to assess the reliability of hull girders subjected to extreme bending moments. The methodology is based on ultimate strength assessment of hull-girder bending using an incremental strain compatibility method. Two reliability assessment methods-(1) advanced second moment (ASM) method, and (2) Monte Carlo simulation (MCS) method with variance reduction techniques-were employ ed for structural reliability assessment of hull-girder bending of sur face ships. This study demonstrates the structural reliability evaluat ion of hull-girder bending of ships (1) by considering its strength pa rameters as random variables, and (2) by considering a non-closed perf ormance function using both reliability methods. This technique can al so be applied to a closed-form expression of the performance function. Utilizing such a methodology, ultimate strength and loads for hull-gi rder bending can be developed individually as modules, and then combin ed into a non-closed form in a performance function. Simulation method s are also used to assess the uncertainty in hull girder strength due to uncertainties in basic random variables. Examples using the ASM and MCS methods for reliability assessment are also presented.