Seismic performance of eccentrically braced frames using codal provisions: a comparative design study

Seismic design provisions for eccentrically braced frames (EBFs) have undergone significant evolution in recent years, with major building codes continually refining their guidelines. This study presents a comparative analysis of the seismic design provisions in current standards, with a focus on key aspects including overstrength factors, behavior factors, and structural response under seismic loads. Unlike many previous studies that focused on a single design standard, this research highlights the differences between two codes and the implications for seismic resilience. A detailed case study of a multistory office building in Naples, Italy, where EBFs are designed in accordance with the studied guidelines, is presented. The study examines the impact of variations in link beam length, bracing configurations, and material properties (S275 and S355 steel) on seismic performance. Using commercially available software for structural analysis, including response spectrum analysis and second-order (P-Δ) effects, the study reveals significant differences in overstrength distribution, lateral drift limits, and energy-dissipation mechanisms. Notably, one code assigns variable behavior factors based on ductility class, whereas the other uses a fixed response modification factor. These differences influence base shear requirements, overstrength provisions, and material efficiency. The findings offer practical insights for structural engineers in selecting an appropriate design approach based on seismic performance objectives. Future research should focus on parametric studies and full-scale testing to further refine EBF design methodologies and contribute to the harmonization of global seismic design standards.