Browsing by Author "Padilla-Llano, David A."
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- 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.
- Test Videos - Compression-Tension Hysteretic Response of Cold-Formed Steel C-Section Framing MembersPadilla-Llano, David A.; Moen, Cristopher D.; Eatherton, Matthew R. (2012-06-19)This paper summarizes results from an experimental program designed to evaluate the tension-compression cyclic axial response of cold-formed steel Csection structural framing members. A new cyclic loading protocol for coldformed steel members is presented that defines the target axial displacement based on elastic buckling parameters. The protocol is used to explore the cyclic response of members experiencing local buckling, distortional buckling, and global buckling deformation. In the experiments, post-bucking energy dissipation was observed along with tension stretching and softening. The quantity of dissipated energy per cycle increased as cross-section and global slenderness decreased. Specimens experiencing local and distortional buckling dissipated more energy per half-wavelength than those experiencing global buckling.