Improving the Shear Capacities of Lipped Channel Beams with Web Openings Using Plate Stiffeners

Abstract

Cold-formed steel lipped channel beams (LCBs) are used extensively in residential, industrial, and commercial buildings as load-bearing structural elements. Their shear capacities are considerably reduced when the web openings are included for the purpose of locating building services. Past research has shown that the shear capacities of LCBs were reduced by up to 70% due to the inclusion of these web openings. Hence there is a need to improve the shear capacities of LCBs with web openings. A cost-effective way of eliminating the detrimental effects of large web openings is to attach suitable stiffeners around the web openings and restore the original shear strength and stiffness of LCBs. Hence detailed experimental studies were undertaken to investigate the behavior and strength of LCBs with stiffened web openings subject to shear, and combined bending and shear actions. Both plate and stud stiffeners, with varying sizes and thicknesses, were attached to the web elements of LCBs using different screw-fastening arrangements. Simply supported test specimens of LCBs with aspect ratios of 1.0 and 1.5 were loaded at midspan until failure. Numerical studies were also undertaken to investigate the strength of LCBs with stiffened web openings. Finite-element models of LCBs with stiffened web openings under shear, and combined bending and shear actions, were developed to simulate the behavior of the tested LCBs. The developed models were then validated by comparing their results with experimental results and were used in further studies. Both experimental and finite-element analysis results showed that the stiffening arrangements recommended by past research and available design guidelines are not adequate to restore the original shear strengths of LCBs. Therefore, new stiffener arrangements were proposed based on screw fastened plate stiffeners. The details of the research reported in this paper are presented.