Local buckling of RHS members under biaxial bending and axial force

This paper aims at providing an in-depth analysis of the local plate buckling coefficients for thin-walled rectangular hollow sections (RHS) subjected to biaxial bending and/or axial force. For the determination of these coefficients, a computational efficient Generalised Beam Theory formulation is implemented in a MATLAB code, capable of calculating accurate local buckling loads with a very small computational cost and, therefore, making it possible to conduct extensive parametric studies in a very short period of time. Taking advantage of the small longitudinal half-wavelength nature of the local buckling mode, semi-analytical solutions using sinusoidal half-wave amplitude functions may be employed for the GBT cross-section deformation modes. The code then computes the lowest local buckling load by varying the member length and using the “golden-section search” algorithm. Although most of the paper is devoted to cross-sections without rounded corners, the code is also capable of handling rounded corners and a preliminary study concerning its effect on the buckling coefficients is also presented.