Reliability of perforated cold-formed steel channel-section beams using FORM method

Resumo

Cold-formed steel (CFS) members can be designed with the AISI Direct Strength Method (DSM) which
utilizes the local, distortional, and global elastic buckling properties of a cross-section to predict ultimate strength.
The Brazilian standard also includes the DSM, but does not consider the presence of holes in the section. This
paper develops the reliability assessment of beams, designed based on available methods in the literature adapted
for sections with perforation. Such methods have their origin in the Direct Strength Method. An experimental
database of cold-formed steel channel-section beams was established. Using this database, a statistical analysis of
test results was conducted to determine the probability distribution function that provides the best fit to the
professional factor data and the distribution parameters. The statistical parameters of professional factor, material
strength, geometrical properties, load type, and load ratio were considered in the reliability evaluation. Then, the
structural reliability indexes of beams subject to the local and distortional buckling modes were evaluated using
the first order reliability method (FORM). The results showed that the target reliability index of 2.5 was not reached
when the load combination of the Brazilian code was applied for profiles susceptible to the distortional buckling
mode.