In the design of cold-formed steel buildings, shear walls are typically used to provide lateral resistance for seismic or wind load. The wood sheathing, such as oriented strand board, is screw-fastened to the cold-formed studs and tracks to develop shear stiffness as well as strength in the wall system.
The composite shear wall response is dominated by the local behavior at each steel-fastener-sheathing connection. Researchers from Johns Hopkins University and Bucknell University cur-rently conduct research addressing this topic. They extend the development of a mechanics-based approach to predict lateral response of wood sheathed cold-formed steel (CFS) framed shear walls.
An OpenSees model is developed that uses standard beam-column elements for the framing members and a rigid diaphragm for the sheathing. The stud-to-sheathing connections are represented as zero-length springs utilizing a Pinching04 material re-sponse developed based on isolated fastener tests. The OpenSees model is validated against previously conduct-ed, monotonic and cyclic full-scale shear wall tests, and shown to have good general agreement. In addition, the developed force distribution of the fasteners in the studs of a typical shear wall is explored. Work remains to further calibrate the OpenSees model, but the developed results demonstrate that the shear wall response relies on connection deformations and this is the critical nonlinearity. This observation makes the possibility of determining lateral response for gravity walls and wood-sheathed floor diaphragms a distinct possibility- and this capability is critical to better understanding the seismic system-level response of cold-formed steel framed buildings.
Guanbo Bian and Benjamin W. Schafer Johns Hopkins University Baltimore, MD
Stephen G. Buonopane Bucknell University Lewisburg, PA