Reliability of built-up cold-formed steel beams designed by the direct strength method

Resumo

Built-up cold-formed steel (CFS) beams are composed of two or more sections that are joined together with welds, bolts or screws. Although PFF composite bars are commonly used in bending applications, the structural design of these sections requires further investigation. This study proposed a critical review of research related to the structural behavior and designing methodology of these elements. A review of published articles, encompassing experimental studies and numerical simulations of these elements, was conducted. The safety of built-up beams subjected to bending, designed according to the Direct Strength Method (AISI S100, 2016; NBR 14762, 2010), was evaluated and for the statistical study of the model error variable, beam test results obtained from literature were compared to the resistant capacities obtained by the direct strength method (DSM). The structural safety verification of built-up beams was performed using first-order reliability methods to assess the safety level for different load combinations. A calibration procedure for NBR 14762 (2010) was also presented, obtaining the resistance factor for a target reliability index.