“…Steel purlins are considered simple structural members supporting the roof covering and usually designed as hot-rolled or cold-formed elements. In both cases, the most essential parameter to be considered for their safety 1 MSc., Eng., Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, ul. Poznańska 2, 35-084 Rzeszów, Poland, e-mail: mgorski@prz.edu.pl 2 Prof., DSc., PhD., Eng., Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, ul.…”