Date of Award
Master of Engineering (ME)
In the application of cold formed steel structural members, holes are usually cut in the webs of sections for passing pipes or conduits. The Canadian standard for the design of cold formed steel sections does not provide sufficient design information for theses conditions. However, the American Iron and Steel Institute has recently provided design guidelines for sections with circular perforations based on limited available experimental data.
The purpose of this study is to determine the effect of size and shape of openings on the axial load behaviour of cold formed sections having different flat width-to-thickness ratios of webs.
A total of fifty five stub column tests were performed to provide design guidelines for stiffened plates with openings. Cold formed lipped channel steel sections were selected for the tests. Circular, square or slotted holes were cut in the centres of webs. The diameter, or width of the openings, varied from 0 to 0.6 times the flat width of the web. The tests were performed under axial compression and centering of the specimen was done with the help of strain gauges. Load versis axial shortening and out-of-plane deflections curves are plotted. Experimental buckling loads of the sections are obtained using the strain reversal method. Ultimate loads of the stub columns are calculated using the effective width approach given in North American codes. An empirical relationship was derived from the experimental data for the effect of square of circular openings in the web on the strength of cold formed sections.
It was found that the buckling load of a section decreases with respect to the buckling load of an unperforated section when size (diameter or width) of the opening is 20% of the flat width of the web but increases as the size of the opening is increased to 60%. The ultimate strength of sections with circular and square openings changes insignificantly when the size of the openings is 20% of the flat width of web. However, it drops to about 87% when the opening size is increased to 60%.
The shape of the opening influences the degree of reduction in strength. The shapes in increasing order of influence are circular, square and slotted openings. The maximum drop in compressive strength, about 14%, was for the section with a slotted opening, of width of about 48% of the web flat width. It also shows the importance of both the longitudinal and transverse dimensions of the opening. The design guidelines provided by the American Iron and Steel Institute (1986) are conservative. The equation proposed herein accurately predicts the effect of square or circular perforations on the strength of the cold formed steel sections.
Banwait, Avnash Singh, "Axial Load Behavior of Thin Walled Steel Sections with Openings" (1987). Open Access Dissertations and Theses. Paper 2686.