Void-Filled SHS Beams Subjected to Large Deformation Cyclic Bending

Abstract

Local buckling and plastic hinges may occur in the compression flange of square hollow-section (SHS) beams under high amplitude cyclic bending arising from earthquakes. Once a local mechanism forms, residual strength rapidly reduces within a few cycles. This is even true for compact sections that have adequate rotation capacity under static bending. This paper compares the behavior of empty, and void-filled, cold-formed square hollow sections subjected to large deformation cyclic bending. A model is developed to estimate the ultimate moment capacity of void-filled SHS beams. The filler material used was normal concrete, low strength concrete, lightweight concrete and polyurethane. Experimental results show that void filling significantly increases ductility—and thus the number of bending cycles SHS beams can be subjected to—in overloaded situations.