Stephen Buonopane, Associate Professor of Civil & Environmental Engineering
The lateral behavior of sheathed, cold-formed steel (CFS) framed shear walls depends considerably on the complex behavior that occurs at each fastener location. Screw fasteners attach the sheathing material to the CFS framing, but relative motion of these components creates local damage, resulting in non-linearity at the scale of the entire shear wall. A computational model of a CFS shear wall is developed in which each fastener is represented by a non-linear, radially-symmetric spring element. The material parameters of the fastener element are determined from physical tests of sheathing-to-stud connections with small numbers of fasteners. The fastener material model includes a softening backbone curve, pinching, and loading and unloading parameters. The remainder of the model employs rigid sheathing panels, beam-column elements for framing, semi-rigid rotational springs for stud-to-track connections, and springs for hold-downs. The models are subjected to lateral cyclic displacement histories using the OpenSees structural analysis software. Thirteen full-scale shear wall tests of two different widths are modeled with various construction details related to the ledger track, gypsum board, vertical and horizontal seams, and number and thickness of field studs. The computational analyses are compared to the full-scale physical tests based on load-displacement behavior, lateral strength, drift at failure, initial stiffness, and energy dissipation, and are compared to specification-based strengths and displacements. The computational models provide detailed information on forces in the framing members and interaction forces at individual fasteners. This fastener-based computational approach is able to efficiently reproduce key aspects of the lateral behavior of CFS shear walls. (C) 2015 Elsevier Ltd. All rights reserved.
Buonopane, Stephen; Bian, G.; Tun, T. H.; and Schafer, B. W. “Computationally Efficient Fastener-Based Models of Cold-Formed Steel Shear Walls with Wood Sheathing.” Journal of Constructional Steel Research 110, (2015) : 137-148.