Virginia Tech Structural Engineering and Materials Report Series
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Browsing Virginia Tech Structural Engineering and Materials Report Series by Subject "Cold-formed steel"
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- Energy Dissipation for Cold Formed Steel ConnectionsHaus, Andreas (2014-02-18)
- Energy Dissipation of Thin-Walled Cold-Formed Steel MembersPadilla-Llano, David A.; Moen, Cristopher D.; Eatherton, Matthew R. (2013-10-02)Design of cold-formed steel (CFS) structures subjected to lateral seismic forces traditionally relies on the cyclic strength of subassemblages such as strapped/sheathed shear walls. Little regard is paid to the behavior of the individual components, their contribution to the lateral resistance of CFS structures, or to the actual seismic behavior of the structure as a whole. Understanding the cyclic behavior at the individual component level is necessary to develop accurate and computationally efficient models, a toolbox of nonlinear elements, capable of accurately and efficiently simulating the seismic behavior of CFS members and the infinite number of possible configurations in cold-formed steel structures. This report summarizes results from a research program designed to investigate the cyclic behavior and energy dissipation of cold-formed steel C–sections structural axial and flexural framing members. Twenty four axial tests and 24 flexural tests were performed to evaluate the energy dissipation characteristics of axial and flexural members experiencing global, distortional and local buckling deformations. Specimen cross-section dimensions and lengths were selected to isolate the specific buckling modes. A cyclic loading protocol is adapted for cold-formed steel members to evaluate the energy dissipation characteristics. The protocol target displacements are defined based on elastic buckling properties. Experimental data is utilized to calibrate a hysteretic model that represents the cyclic response of cold-formed steel C-section structural framing members. The model includes strength degradation, unloading stiffness degradation and pinching behavior of the observed experimental response. Model parameters and damage rules are calibrated for local, distortional and global buckling based on the hysteretic energy dissipated. The calibrated parameters can be utilized to develop a toolbox of nonlinear hysteretic springs to represent framing axial members in CFS structures for seismic analysis and facilitate performance based earthquake engineering of CFS structures.
- Stiffness and Strength of Single Shear Cold-Formed Steel Screw-Fastened ConnectionsPham, Hong S.; Moen, Cristopher D. (2015)Results are presented from an experimental program on single shear cold-formed steel-to-steel through-fastened screw connections, including documentation of the complete load-deformation response and stiffness degradation. Ply thicknesses from 0.88mm to 2.58mm and screw diameters of 4.17mm to 5.49mm were tested to cover the practical range of applications common to cold-formed steel framing. A custom non-contact optical technique measured steel ply relative displacements and screw tilting angles. Fastener load-deformation response is presented in a format that can be incorporated into codes and standards for system level design calculations that require connection stiffness to quantify load sharing. The simplified multi-linear curves characterized from monotonic responses can also serve as nonlinear springs in cold-formed steel subsystem computational models (e.g., shear wall, floor diaphragm, roof truss) and 3D whole building cold-formed steel structural simulations.