Development of a novel haunched link for eccentrically braced frames

The seismic performance of eccentrically braced frames (EBFs) is strongly influenced by the length of their links. In these frames, short links undergo shear yielding, long links experience flexural yielding, and intermediate links go through a combination of shear and flexural yielding. Hence, shorter links have a greater inelastic rotation capacity than longer links. However, having the option to use longer links is architecturally preferable as it allows the designer to place larger openings in the walls of braced bays. This paper proposes the use of haunched links instead of intermediate and long conventional links in order to accommodate architectural considerations without undermining seismic performance. In the proposed design, the depth of the middle section of the link is reduced so as to ensure that shear yielding will always take place in this area. Finite element modeling, validated with experimental data, is used to study the behavior of the haunched link and compare it with conventional links. The results show that the proposed haunched link has a higher inelastic rotation capacity and energy dissipation capacity than conventional links. They also indicate that an EBF with haunched links will have a higher deformation capacity and ductility than a similar EBF with conventional links.