Behaviour of thin-walled steel box sections with or without internal restraint

In this paper a comprehensive series of tests is described and presented. The tests were performed to examine the behaviour under axial load of short, thin-walled, square steel tubes with or without internal restraint. The influence of specimen length on the local buckling strength was also investigated. The specimens had width-to-thickness ratios of between 37.3 and 130.7 and length-to-width ratios ranging from 0.77 to 2.91. Two test series were performed. In Series 1 the effect of changing the buckling mode by forcing the formation of outwards buckles was examined for a wide range of width-to-thickness ratios. In Series 2 the influence of specimen length on the formation of local buckles was examined by using thin-walled steel tubes with and without internal restraint. The material properties, residual stresses and geometric imperfections have been measured. The test strengths have been compared with strength models in design standards and specifications. Improved recommendations for design have been made. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.