Numerical and Experimental Investigation of Higher Capacity Cold Formed Steel Shear Walls.

Abstract

In this research project, three unique, higher-capacity cold-formed steel (CFS) shear wall configurations are proposed and tested, with the aim of extending CFS framing applications into mid-to-high rise buildings. The shear wall configurations consist of a concentric-sheathed shear wall with built-up hat section studs, a concentric-sheathed shear wall with an intermediate stud located at mid-span, and a diagonally strapped concentric sheathed shear wall with built-up hat section studs. A preliminary, full-scale testing program was carried out in collaboration with Chongqing University that included monotonic and cyclic tests of the shear wall specimens, cyclic tests of screw connection assemblies in double shear, and coupon material tests. The test results were analyzed using the Equivalent Energy Elastic Plastic (EEEP) method and the analysis results indicate that the shear walls investigated herein attained substantially higher strengths and ductility than code approved shear walls. Numerical non-linear shell finite element models of each specimen was established and calibrated using the experimental results. To overcome convergences issues, the explicit solver was employed. The finite element results demonstrated good correlation with the experimental results for all shear wall configurations, with the exception of the diagonally-strapped specimen. The verified numerical models were then used to conduct an extensive parametric study, where the influence of several parameters such as screw spacing, stud and sheet thickness, and aspect ratio were assessed. An analytical model for predicting the monotonic response of the concentric-sheathed wall and a simplified method for determining the axial force and bending moment demand on the boundary studs are proposed. Both methods consider semi-rigid behaviour in the boundary frame of the shear wall and have showed good agreement with the shell finite element results, suggesting that the methods can be used for preliminary design purposes.