Structural reliability for the design of cold-formed steel I-sections members undergoing web crippling under interior loading conditions

Resumo

Cold-formed steel sections (CFS) are subjected to different buckling modes. This work presents the
results of structural reliability analysis of web crippling strength expression currently used in the Brazilian
Standard, with a particular focus on I-sections (Stiffened Flanges) beams subjected to the loading conditions of
Interior-One-Flange (IOF). Previous research studies of web crippling showed that I-sections members fastened
to the bearing plate (support), subjected to IOF load case, presented inadequate reliability indexes (β) when
compared to the target reliability index. Experimental data of I-sections members reported in the literature were
analyzed to obtain the professional factor statistics. The First-Order Reliability Method (FORM) was used for
the standard calibration procedure. The reliability analysis was developed for load combinations found in the
North American and the Brazilian standards, in addition to the nominal live-to-dead load ratio, Ln/Dn, equal to 3
and 5. Target reliability indexes usually used in the calibration of the main international standards for CFS
members were considered. It was found that the resistance factor present in the Brazilian standard should be
increased for the I-sections members. A revision is necessary to standardize the level of safety of the design to
the limit state of the web crippling.