Practical formula of critical local buckling load of thin-walled members under axial compression based on direct strength method

In order to propose a practical formula of critical local buckling load based on the direct strength method, the background and nature of the direct strength method and the effective width method for calculating the ultimate strength of local buckling of thin-walled members under axial compression are analyzed. Physical significance of local buckling load Pcr, Lis revealed. Selection criteria on Pcr, Lfor the two methods is proposed. A practical formula of critical load Pcr, L, considering plate-assembly effects, is proposed. The accuracy of the proposed formula is verified by comparing its results with the exact values computing by the general beam theory software, GBUTL. The correctness of the selection criteria is also confirmed by comparison. The ultimate loads of C-section thin-walled member are computed by the proposed formula and direct strength method. Comparison with numerical results indicates that the proposed method yields reasonable predictions for the critical load of local buckling. The superiority of the Pcr, Lpractical formula is shown by comparing with the values from the current national standard GB 50018-2002. The results show that the Pcr, Lformula considering plate-assembly effects is required by the direct strength method, and the proposed formula is of simple form and of significantly improved accuracy. © 2016, Editorial Office of Journal of Building Structures. All right reserved.