Experimental and numerical study of torsional buckling of stiffeners in aluminium panels

Ultimate strength of stiffened aluminium panels exhibiting primarily torsional buckling is investigated by experimental and numerical analysis. Such failure modes are of particular interest in flat bar/bulb stiffeners, which are attractive from a fabrication point of view. Current approaches to assess torsional strength are uncertain. For instance, formulations for torsional buckling of stiffeners in steel panels are still debated. In the present paper, an experimental and numerical investigation of torsional buckling strength of longitudinal flat - bar stiffeners in aluminium panels subjected to axial compression is carried out. All 25 stiffened plates with various aluminium material (AA5083 H116 and AA6082 temper T6), web height, thickness were tested. Some test results are presented and compared with numerical calculation using ABAQUS (1998), considering initial deflection, welding residual stresses, as well as heat affected zones (HAZ). The experimental and numerical results are also compared with buckling strength formulations used in DNV Rules for Classification of High Speed and Light Craft (1996), NORSOK (1998) for steel, using the relevant values of the modulus elasticity and yield strength of aluminium, as well as the most recent Eurocode 9 (1998) for aluminium.