Synthesis of welded grillages to withstand compression and normal loads

Abstract

This paper describes the development of the structural analysis theory and procedures which are to be used in an automated minimum weight grillage synthesis program based on the SUMT solution method of nonlinear mathematical programming. All anticipated ductile failure modes for typical welded ship type deck and bottom grillages under uniform normal and biaxial in-plane loading are considered, using both past and recent analytical and experimental research. Emphasis has specifically been placed on compression modes of failure. These include ‘panel’ collapse of longitudinal stiffeners between transverses in' either the column (or strut) collapse mode or the tripping mode, including the effect of welding residual stresses. Also considered is general instability or ‘grillage’ collapse in which any degree of rotational constraint may be considered to act at the boundaries. In contrast to the more usual ‘stress’ analysis, emphasis throughout the paper is on ‘strength’, or the inability of the structure to carry further load, although stress constraints are used where appropriate.