Interactive buckling of thin-walled beam-columns with intermediate stiffeners or/and variable thickness

The design of thin-walled beam-columns must take into account the overall instability and the instability of component plates in the form of local buckling. This investigation is concerned with interactive buckling of thin- walled beam-columns with central intermediate sti€eners or/and variable thickness under axial compression and a constant bending moment. The columns are assumed to be simply supported at the ends. The asymptotic expansion established by Byskov and Hutchinson (1977: Byskov, E. and Hutchinson, J. W. (1977). Mode interaction in axially sti€ened cylindrical shells. AIAA J., 15(7), 941±948) is employed in the numerical calculations performed using the transition matrix method. The present paper is a continuation of the papers by Kolakowski and Teter (1995a,b: Kolakowski, Z. and Teter, A. (1995a). Interactive buckling of thin-walled closed elastic column-beams with intermediate sti€eners. Int. J. Solids Structures, 32(11), 1501±1516; Kolakowski, Z. and Teter, A. (1995b). In¯uence of local post-buckling behaviour on bending of thin-walled elastic beams with central intermediate sti€eners. Engineering Transactions, 43(3), 383±396) and Teter and Kolakowski (1996: Teter, A. and Kolakowski, Z. (1996). Interactive buckling of thin-walled open elastic beam-columns with intermediate sti€eners. Int. J. Solids Structures, 33(3), 315±330) where the interactive buckling of thin-walled beam-columns with central intermediate sti€eners in the ®rst order approximation was considered. The paperʹs aim is to improve the study of the equilibrium path in the post-buckling behaviour of imperfect structures with regard to the second order non-linear approximation. In the solution obtained the transformation of buckling modes with an increase of the load up to the ultimate load, the e€ect of cross-sectional distortions and shear lag phenomenon is included. The calculations are carried out for a few beam-columns