BUCKLING BEHAVIOUR OF STIFFENED PANELS UNDER STATIC AND DYNAMIC LOADING WITH PARTICULAR EMPHASIS ON THE RESPONSE OF THE STIFFENER OUTSTANDS

摘要

This paper presents results on the buckling behaviour of stiffened panels loaded axially under static loading and dynamically under transverse blast pressures. Particular emphasis is placed on the torsional behaviour of the outstands. The study has been carried out using non-linear finite element (FE) packages and plastic mechanism techniques. For the static analysis, an FE package (LUSAS) has been used to obtain load deflection curves, including both the peak load and the unloading characteristic for a range of geometries. Comparisons with experimental results has also been carried out in order to establish the validity of the mesh and the boundary conditions adopted in the FE study. Results from a previous plastic mechanism technique developed to predict the unloading response of a tripping failure in a flat-bar stiffened panel have also been compared with the FE results and the mechanism approach has been combined with a simple elastic loading line to predict an upper bound failure load for the panel. The method compares well with the FE results and gives good correlation over a range of plate slenderness. The responses of stiffened panels subjected to blast loading have also been investigated using various pressure time curves. Both a simple model, consisting of a flat-panel and an individual stiffener and a more complex model of a complete blast wall have been analysed. The analysis package (DYNA3D) accounts for material and geometric non-linearities and strain rale effects which can significantly influence the capacity of the panel. As for the static results, the dynamic analyses have been correlated with previous experimental results. The effect of tripping is shown to have a significant influence on the response, and earlier yield of the panel, when the stiffeners are in compression, is highlighted. It is also shown that provided there is adequatein-plane support to allow the panels to develop membrane action, blast pressures exceeding one bar can be resisted.