Open Collections

Zhang, Peng

University of British Columbia

For designing Cold-Formed Steel (CFS) structural members under compression, AISI S100 (2016) incorporates the Direct Strength Method (DSM). Although the DSM has been used for quite some time, its buckling strength curves have issues and have not been thoroughly assessed with experimental data. In this study, buckling strength curves in the DSM were first assessed with an extensive experimental database containing axial strengths, failure modes, and design parameters of 453 solid and 228 perforated CFS columns. This exercise helped determine the merits and shortcomings of the buckling strength curves. Then, the buckling strength curves were assessed further, using full-section tensile yield strengths as design parameters instead of the virgin material tensile yield strengths. For determining the full-section tensile yield strengths of the columns, i) the model developed by Karren (1965) to predict the tensile yield strengths of CFS corners was modified to improve the accuracy and extend its application limit, and ii) the expression proposed by Karren (1965) for estimating the full-section tensile yield strengths of CFS members was modified to simplify its application. Strength estimations of the columns calculated using full-section tensile yield strengths were compared with those calculated using virgin material tensile yield strengths. Then its potential was tested whether the former could be more accurate and used than the latter after the buckling strength curves are recalibrated. Afterwards, compression tests were performed on 55 CFS columns having patterned perforations distributed along the length uniformly to enlarge the experimental database of perforated CFS columns. The columns had three different cross-sections, and each cross-section had seven different lengths varying from 250 mm to 2150 mm to capture different buckling failure modes. Before conducting the tests, extensive eigenbuckling analyses were performed for the columns, and a method was proposed to accurately determine the lower bound of elastic local and distortional buckling loads and the associated buckling half-wavelengths of perforated CFS columns. Finally, new buckling strength curves were proposed, and their LRFD (Load and Resistance Factor Design) resistance factors (φc) were calculated for a target reliability index of 2.5.

Text

2022-01-06

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/80578

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/