Image-based analysis of steel sheathed cold-formed steel shear wall buckling behavior

The high lateral force resisting feature of the cold-formed steel structure, make it an attractive design choice in seismic zones. The shear strength of these systems controls by two critical factors, the characteristic of the sheathed and the sheathing-to-frame connections. There are many challenges associated with testing different configurations of these thin-wall structures (size, layout, sheathed material). Despite the huge growth of such constructions, the design procedure and the numerical calculation developed by the American Iron and Steel Institute provision AISI S240 (2015) and AISI S400 (2015), didn’t provide a proper standard for the various possible design of the CFS shear walls. This thesis proposes a study aiming to expose the gap across the theory to the practical issue by comparing the equation-based analysis and the image-based analysis of the shear strength of the shear walls. Two large-scale CFS shear walls infilled with gravity wall were tested under the quasi-static reversed cyclic protocol at the laboratory of the University of California San Diego. These innovative specimens were built with the thicker framing members than the listed ones in the AISI standard and assembled in the specific framing layout. The sheathing-to-frame connections and sheathing parameters like screw spacing, screw size, and thickness of the sheet was the same in both walls. The shear strength of these walls computed through the effective Strip width method in the provisions of the AISI S400 (2015) by selecting the minimum value between the shear capacity of the connections which bar the shear force in the tension field and the shear strength of the sheathed. Surprisingly the calculated result was one-third of the test results. This experiment shows how imperfect is the provided equation-based shear strength method by the AISI standard design for CFS Structures.