Cold-formed steel framing walls with infilled lightweight FGD gypsum Part I: Cyclic loading tests

In order to improve lateral stiffness and shear strength of cold-formed steel (CFS) framing wall, an innovative CFS wall with infilled lightweight flue gas desulfurization (FGD) gypsum is presented in this paper. For this purpose, six full-scale specimens were tested under cyclic lateral loads. The density and compressive strength of the infilled gypsum were varied to investigate their impacts on lateral stiffness and shear strength of the walls. The failure modes, load-displacement responses, deformability, and energy absorption capacity of the specimens were also investigated. Test observations showed that the infilled gypsum behaved as a diagonal bracing along with wall frames to resist shearing forces. In addition, the failure modes of the infilled walls were characterized by bond-slip cracks between infilled gypsum and wall frames, as well as compressive failure at the corners of gypsum pieces. The peak loads of the infilled specimens were improved by 1.72-2.54 times compared with the unfilled. Besides, the improvement in shear capacity and lateral stiffness of the infilled walls were obtained by increasing compressive strength of the infilled gypsum. When filling identical gypsum into the walls, one with the bigger stub spacing and the stronger sheathing material had the greater lateral stiffness and shear capacity. In addition, a method for determining the resistance factor gamma(R) of the infilled specimens was proposed in the paper, which can be used for seismic design.