Numerical Investigation of Australasian Cold-Formed Steel strap-braced walls under lateral and vertical load

Abstract

Cold-Formed Steel (CFS) gained popularity in residential buildings due to its dimensional accuracy, lightweight, resistance to shrinking and creeping, durability, low embodied carbon and CNC manufacturing abilities. The materials of CFS structures in New Zealand and Australia are higher strength and thinner gauge than those used in the Northern Hemisphere. The low-rise applications in New Zealand have shown excellent performance since 2010 to 2016 earthquakes. The rapidly growing demand for CFS in mid-rise buildings up to 6 storeys necessitates a different approach to that currently used in bracing and wall systems in two-storey buildings, which is the current limit on most CFS construction. The study investigates the behaviour of a proposed typical 0.95mm thick, grade 550 steel CFS strap-braced panel under lateral and vertical loading in the form of a seismic force-resisting system in SAP2000. The tension strap-braces are yielded to accommodate seismic overloading and resist the failure of the connections, studs, chords or tracks using capacity-design principle. Various configurations of strap-braces have been implemented and compared with the requirements of inter-storey drift of NZS 1170.5. The one-sided and both-sided strap-braced configurations resulted in the strength and stiffness requirements of the standard. A basis is formed for tension, compression and shear transfer mechanisms within the wall and from the wall to the foundation system. The horizontal and vertical stiffnesses of the wall/floor/wall connections on the wall’s overall response are studied. The numerical analyses of the models show potential for such walls to be implemented in mid-rise buildings in New Zealand.