ABSTRACT
Semi-analytical membrane stress-based methods for estimating plate ultimate strength offer important benefits to early stage ship design and structural optimization of large stiffened plate structures. Using these methods, it is feasible to rapidly design an efficient and safe structure for new and unique vessels from first principles. Membrane stress methods predict plate collapse by directly solving the governing equations of plate bending under large deflection. These methods are lower fidelity than finite element methods, but with significantly lower setup and computational expense. Combined longitudinal compressive/tension, transverse compressive/tension, edge shear, and lateral pressure loads can all be considered. However, the existing method does not accurately capture the effect of lateral pressure loads. This paper presents an adjustment to the membrane stress method that improves the accuracy of plate collapse prediction for plates subject to combined loads including lateral pressure. The lateral pressure load is treated differently depending on the relative magnitudes of the added deflection due to lateral pressure in the single and critical half-wave number shape. This approach is compared with results from the finite element model program FEMAP with a NASTRAN solver. Accuracy of the membrane stress-based ultimate strength prediction is significantly improved, at minimal computational expense, making it well-suited to set-based ship design and trade space exploration where many variants of a structural design must be analyzed in a short time.
