Collapse Behavior of Hollow Structural Section Columns under Combined Axial and Lateral Loading

Abstract

Hollow structural sections (HSS) are used as columns in frame systems because of their ability to efficiently resist multiaxial loads. While the majority of previous studies of special moment frames (SMFs) focused on wide flange columns, HSS columns can provide a means of increasing the versatility of SMFs. In order to fully explore the use of HSS columns in SMFs, the collapse behavior of HSS columns subject to combined axial and lateral loading is computationally studied. Seventeen different HSS profiles are selected to cover a wide range of local and global slenderness ratios, including width-to-thickness ratio (b/t), depth-to-thickness ratio (h/t), and the global slenderness ratio about the weak axis (L/ry). Detailed finite element studies show that the behavior of HSS columns is highly dependent on the local slenderness ratios and the level of initial applied axial load (P/Py). A regression analysis is performed leading to a proposed design aid for HSS columns in SMFs along with updated highly ductile local slenderness limits. The proposed highly ductile limits suggest that the current AISC limits for HSS columns are conservative when considering the width-to-thickness ratio and potentially unconservative when considering the depth-to-thickness ratio.