Second‐Order Effects on EBF Yielding Links: New Design Equations for Overstrength and Capacity

Abstract Previous studies have shown that links in eccentrically braced frames (EBFs) can be subjected to axial loads. Both shear and flexural links exhibit increased shear strength under tension and a reduction in shear capacity under compression. While AISC 341 and CSA‐S16 provide equations for accounting for these effects, these equations are primarily based on the yielding interaction between normal and shear stresses, in shear links, and section‐level axial‐flexure (P‐M) interaction, in flexural links, without considering second‐order effects. Although the former mechanisms could affect the capacity of shear links, their impact is less significant. For flexural links, the P‐M interaction is negligible for low axial load levels that are expected in EBF applications. The present study shows that axial load effects on links in EBFs are primarily due to second‐order effects. A detailed discussion on quantifying axial loads in EBF links and their effects is provided, and new design equations are developed to account for such effects. The proposed equations are validated using previously done full‐scale experimental results and supplementary finite element analyses, resulting in significantly improved accuracy in predicting the axial load effects compared to existing design expressions.