CILAMCE-PANACM-2021 Proceedings of the joint XLII Ibero-Latin-American Congress on Computational Methods in Engineering and III Pan-American Congress on Computational Mechanics, ABMEC-IACM Rio de Janeiro, Brazil, November 9-12, 2021 Structural reliability for the design of cold-formed steel I-sections members undergoing web crippling under interior loading conditions Nathália Barbosa de Melo 1 , Marcílio S. R. Freitas 1 , André L. R. Brandão 2 1 Dept. of Civil Engineering, Universidade Federal de Ouro Preto Campus Universitário Morro do Cruzeiro, 35400-000, Ouro Preto, Minas Gerais, Brasil nathalia.bm@aluno.ufop.edu.br, marcilio@ufop.edu.br 2 Dept. of Civil Engineering, Universidade Federal de Itajubá Rua Irmã Ivone Drumond, 200, Distrito Industrial, 35903-087, Itabira, Minas Gerais, Brasil andreriqueira@unifei.edu.edu Abstract. 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, L n /D n , 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. Ke ywor ds: cold-formed sections, FORM method, web crippling. 1 Introduction This work aims to evaluate the safety of cold-formed steel sections subjected to concentrated load in regions without transverse web stiffeners (web crippling), with an initial focus on I-sections with stiffened flanges. Research related to the application of structural reliability in design standards has been carried out in Brazil. Regarding the standards for cold formed sections, the works by Freitas et al. [1, 2], Brandão [3, 4] , Brandão et al. [5, 6, 7] and Toledo [8]. The design criteria used in this work were obtained from NBR 14762 [9]. The reliability index (β), obtained by the FORM method, was used in the calibration of resistance factors and will be compared with target reliability indexes (β o ), obtained in the calibration of the North American Specification (NAS) [10]. The reliability index was also evaluated by the Second-Order Reliability Method (SORM) and by the Monte Carlo Simulation (SMC) by computational routines with the application of CalREL software [11]. It is noteworthy that the NAS was calibrated by First Order Second Moment Method (FOSM). In FOSM, the probability distribution function is ignored, unlike more precise methods such as FORM, SORM and SMC used in this work. A new proposal for formatting the design methodology provided in NBR 14762 (2010) will be presented, defining different resistance factors for different load cases.