Effect of Width-Thickness and Depth-Thickness on the Cyclic Flexural Buckling Behavior of Hollow Structural Sections

HSS members are desirable for structural applications due to their flexural, compression, and torsional resistance. To allow for increased utilization of hollow structural sections (HSS) in cyclic bending applications, their cyclic flexural stability and local buckling behavior under large rotations must be understood. Experimental tests of HSS with width-thickness (b/t) and depth-thickness (h/t) ratios of 8.46 to 31.3 and 19.9 to 48.5, respectively, show their suitability for cyclic bending applications provided b/t and h/t are limited. The effect of the b/t and h/t ratios are found to be interdependent and correlate with the occurrence of local buckling and loss of moment capacity with cycling to increased deformation levels. In order to better understand the behavior of HSS beam members under cyclic loads, a finite element model (FEM) that accounts for localized material properties and local buckling behavior is developed and correlated to experimental results. Geometric perturbations of the section geometry are introduced based on an eigenvalue buckling analysis to approximate observed experimental local buckling behavior. From the correlated model, 133 sections are analyzed, with the section sizes spanning from HSS 152.4x50.8x4.8 to HSS 508.0x304.8x15.9, allowing a wide range of b/t and h/t ratios to be considered. The results confirm the interdependence of b/t and h/t on the local buckling behavior and provide a basis for defining limiting values to prevent local buckling and subsequent loss of moment capacity under cyclic bending loads.

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