Strength of steel and aluminium alloy ship plating under combined shear and compression/tension

The load shortening curves are essential to the estimation of ultimate strength of ship structures under longitudinal bending in the simplified progressive collapse method. Longitudinal bending is the dominant load on ships structures, but in cases where the ship is heading to oblique seas and/or there are large openings in the structure due to its design (i.e. containerships) or due to damage (i.e. grounding, collision, blast), torsional loads may also be important when calculating ultimate strength and further investigation is required. Torsional loads on ship structures generate shear stresses which are carried primarily on the ship's plating, therefore the effect of shear on the in-plane load shortening behaviour of ship plating is thoroughly investigated in this paper. Initially, marine grade steel and aluminium alloy plates with different aspect ratio (1-4) and slenderness (1-5) are subjected only to shear loads. These results show that the plate aspect ratio does not significantly affect the progressive collapse behaviour of plates under shear, hence only square plates are investigated further. Steel and aluminium alloy square plates (5083-H116 and 6082-T6) with slenderness ratio 1-4 are subjected to shear, in-plane compression/tension and combined shear and compression/tension applying the same complex set of boundary conditions for all cases and using ABAQUS CAE. Finally, the generated interaction diagrams of shear and compressive/tensile loads provide essential information for the effect of shear on the progressive collapse of in-plane loaded plates allowing for the incorporation of torsion in the simplified progressive collapse method.