Simplified Models for Elastic Buckling of Cold-Formed Steel Sections Under Localised Loading

Abstract

The main objective of this thesis is to develop a simple and efficient way to calculate the buckling load P_cr of cold-formed steel sections under localised loading, which is an important input in the Direct Strength Method equations for design of cold-formed sections subjected to localised loading cases. The first objective of this thesis is to determine the buckling loads (P_cr) and failure modes of lipped-C sections under localised loading with general end of boundary conditions and four different loading cases by using the Finite Element Method (FEM) software Abaqus. To calculate the buckling load coefficient of lipped C channel sections under localised loading, according to column buckling theory, the buckling width value (b_b) should be calculated. The second objective of this thesis is to determine the buckling width (b_b) from the buckling modes for all four different loading cases by using the Finite Element Method software Abaqus. Subsequently, all the FEM simulation data including the buckling loads (P_cr) and buckling widths (b_b) are collected for a wide range of variables of channel section in a parametric study, as given in Section 3 in this thesis for all four loading cases. The fourth objective of this thesis is to develop the proposed equations for the buckling width (b_b) for lipped-C sections under general localised loading, as given in Section 4.1 of this thesis. The buckling width (b_b) is diffused from the loading width through the radii and web, which is based on observations of buckling modes for different cross-sections and load cases for lipped C-sections under general localised loading from FEM software Abaqus. The fifth objective of this thesis is to calibrate the proposed equations for column buckling coefficient (α) for lipped-C sections under general localised loading, as given in Sections 4.2 and 4.3 of the thesis. The proposed equations are consistent and simplified models for all localised loading cases. In addition, a detailed accuracy check of the final proposed Equation 4.16 is validated against all the simulation data in Section 4.3.5. According to the equations of buckling coefficient (α) and buckling width (b_b), the buckling load P_cr can be calculated simply and efficiently for lipped-C sections under localised loading.