Reliability of cold-formed sections with web holes susceptible to failure by web crippling due to concentrated force

Resumo

Cold-formed steel (CFS) are structural elements widely used in the construction industry and, in many situations, holes in the web is a design necessity, because it facilitates the passage of ducts, wiring and piping. This study evaluates the reliability of cold-formed sections with web holes subjected to concentrated force in sections without transverse stiffeners susceptible to web crippling failure. FOSM (Second Moment and First Order Method) and FORM (First Order Reliability Method) methods were used. A database was created with experimental results extracted from the literature, covering the four loading cases (end-one-flange loading EOF, interior-one-flange loading IOF, end-two-flange loading ETF, interior-two-flange loading ITF) presented in the standards used as reference, North American specification AISI S100 (2016), Brazilian standard NBR 14762 (2010) and European code EN1993-1-3 (2006). To obtain statistical data on the professional factor, one of the variables of the reliability problem, experimental results were compared with theoretical ones obtained by norm equations. Only AISI S100 (2016) standard has a criterion for considering web holes by considering a specified reduction factor for EOF and IOF. The results showed that the web holes significantly reduce the resistance of sections when subjected to the EOF loading case, while they reduce to a lesser extent in sections exposed to the IOF loading case. Analyzing the specimens subjected to the IOF loading, the results showed that another condition that influences the resistance is the fixation of the flanges to the supports. Very similar specimens groups reached the target reliability index when connected to the supports during the tests and did not reach when not connected.