BEHAVIOR OF OVERLAPPING AND OVERHANGINGCOLD FORMED Z-BEAMS

Abstract

Z-section is one of the most common cold-formed purlins. Its lapping ability provides continuity, and double thickness at the support regions. Four different types of systems may be found in modern roofs; single span, double span, multi-span with sleeves and multi-span with overlaps is the most popular. Four verification cases: simple and overhanging beams are conducted, using FEM to investigate the structural behavior of lapped beams over the internal supports in multi-span systems with overlap. Results are compared with code and previous experimental work and good agreement is achieved. In this study, the moment resistance of overhanging Z-purlin with different thicknesses (1.5, 1.6 and 1.8 mm), different heights (142, 172, 202 and 232 mm) and overlap lengths (0.1L to 0.5L), where L is the back span length are investigated under combined bending and shear using ANSYS14.00. For each lap length and height, models are also conducted with and without straps with either restrained compression flanges or not. The different factors and variables affecting the behavior and capacity of these beams are monitored. Modifications for the current design standards and specifications are suggested.

Key words: Cold formed; overhanging beams; Z-beams; Finite Element; lateral torsional buckling; distortional buckling.