Enhanced Seismic Performance of Cold-Formed Steel Strap Braced Walls with Composite Lightweight Concrete Filled Steel Chord Studs

Abstract

Cold formed steel (CFS) strap-braced stud walls are used as the main lateral force resisting system in light gauge steel (LGS) framed construction. Application of LGS construction in high seismic risk regions or high-rise buildings requires the use of high strength strap braced walls. However, the current state of the art configurations of strap braced walls provides only limited lateral strength due to chord studs, which fail by premature buckling as the load demand increases. This study investigates the seismic performance of CFS strap-braced walls by substituting traditional back-to-back chord studs with novel built-up chord (BUC) and composite built-up chord (C-BUC) configurations to improve wall lateral load carrying capacity. Novel BUC and C BUC CFS sections were tested to evaluate their compressive capacities and failure modes, followed by a finite element analysis (FEA) in ABAQUS for model calibration. A CFS strap braced wall model was then developed and calibrated based on existing experimental data. The model was then used to perform parametric study assessing the effects of built-up and composite built-up chords on wall lateral performance under monotonic loading conditions. The results show that novel built-up and composite built-up chords, combined with increased strap sizes, significantly enhanced lateral load-bearing capacity and ductility of wall. Comparison with AISI S400 design guidelines highlights the potential for these configurations to meet advanced seismic demands, advocating for a revision in current standards to include composite CFS systems as primary lateral force-resisting systems.