Experimental buckling criteria for thin pierced plates
Sehested, John H
Vann, W. P.
Master of Science
Tests conducted with a pierced light-gage, cold-formed steel channel were used to evaluate four different criteria for experimentally determining the elastic buckling loads of thin plates. The single test specimen was a ten foot length of a 14-gage section with a nominal 8" web and nominal 3" lipped flanges. The section was loaded as a beam bent about its minor axis so that the web was placed in compression. A constant-moment mid-span region of five times the web width simulated a long plate subjected to in-plane compression. Tests of the unpierced specimen were followed by tests in which the specimen had a single hole in the center of the web. A repetitive process of flanging the plain holes and then cutting off the flanges created a succession of plain and reinforced holes of increasing diameter. A total of thirty-six tests were carried out. The specimen was instrumented with as many as forty electric strain gages and nine dial gages. The four buckling criteria considered were the maximum strain (or strain reversal) criterion, the top-of-the-knee criterion, the inflection point criterion, and the Southwell plot method. The last was judged to be the most accurate and appropriate, and it was applied in studying the effects of the hole on the elastic buckling load. The critical load was found to be insensitive to hole size for both plain and reinforced holes up to a hole diameter of about one-half the plate width. Tests were not conducted for large holes. The addition of a reinforcing lip increased the buckling load by over 50%. The experimental results agree fairly well with the results of a finite element study.