Compression strength of reinforced steel angles

Abstract

A common reinforcing detail for strengthening open web steel joists is the addition of a rod or plate to an existing angle to form a built-up member. Design standards typically include a limit on the spacing of connections between the components of built-up compression members. The limits are based primarily on more common built-up members such as double angles. Reinforced angles are different than double angles because, among other things, the components are in direct contact limiting potential buckling modes. Prior physical testing is limited; thus, it is unclear if the spacing limits are truly applicable to reinforced angles. The limits can govern the weld spacing for reinforced angles in joists, potentially resulting in more welding than necessary. This experimental and numerical study investigates the compression strength of reinforced angles and how the strength varies with weld spacing. Fifteen reinforced angle specimens were fabricated and tested with variation in reinforcement type, weld spacing, and member effective length. Numerical analyses were performed to expand the range of investigation. Weld spacing had essentially no effect on the experimental strength of the test specimens when the weld spacing was less than or equal to 305 mm (12 in.) on center. Strengths computed per current design provisions were found to be overly conservative. Recommendations to modify the provisions were made. These results lead to a better understanding of the behavior of reinforced angles and enable more efficient reinforcement of open web steel joists.