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Author ORCID Identifier

https://orcid.org/0000-0002-5205-0531

AccessType

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Civil and Environmental Engineering

Year Degree Awarded

2021

Month Degree Awarded

February

First Advisor

Kara D. Peterman

Subject Categories

Civil Engineering | Structural Engineering

Abstract

Cold-formed steel (CFS) bearing walls are frequently installed on concrete slabs, which do not provide perfectly rigid and uniform bearing conditions. Existing design guidance assumes bearing conditions have no impact on the axial capacity, though cold-formed steel compressive members are particularly susceptible to end conditions. Studs are typically installed at the edge of concrete slabs, which is prone to spalling and geometric irregularities. Moreover, they are occasionally installed inadvertently overhanging from concrete slabs. In this research project, the impact of non-uniform and partial bearing conditions on the axial strength of cold-formed steel wall assemblies is identified and characterized experimentally and numerically. The results are for a means of evaluating existing design guidelines presented in the North American Specification of the American Iron and Steel Institute (AISI S100-16). Twenty-seven tests were conducted on CFS wall assemblies. Studs of various cross-sections and bearing conditions were considered. Bearing conditions included: full bearing (edge distance ≥ 20.32 cm (8 inches)), close to the edge, at the edge, and partially overhanging from the slab. In addition to the experiments, high-fidelity finite element modeling of all the systems was conducted to validate the experimental and elucidate the impact of parameters not captured during the tests.

Investigated cold-formed stud assemblies were fixed to 30.48 cm (12 inches) in height. However, variable height wall assemblies are utilized in typical construction. To better characterize the relationship between the bearing condition and axial strength, a computational modeling program at heights determined by buckling modes (local, distortional, and global) was conducted. In this program, 2376 high-fidelity 3D finite element analyses were performed. 66 variable stud cross-sections were investigated. The CFS assemblies were installed on concrete slabs in twelve different bearing conditions, from full-bearing condition with no edge effects to intermediate edge distances approaching the edge, to the edge itself, and finally overhanging from the edge.

The experimental and computational modeling results revealed that there is a potential need for improvement of current AISI specifications, where all bearing conditions are assumed rigid and uniform. The experimental-derived and analysis-based design recommendations for improving the current specification are discussed in this dissertation. Furthermore, it was concluded that by loading the end of specimens by the actual and non-uniform stress distribution which were generated by non-uniform bearing conditions, the axial strength could be captured precisely by direct strength method equations proposed in AISI S100-16.

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