Large-Scale Experimental Validation of Optimized Cast Steel Replaceable Modular Yielding Links for Eccentrically Braced Frames

Steel eccentrically braced frames (EBFs) combine the advantages of both moment-resisting frames and concentrically braced frames and provide an attractive seismic design solution. Shear-critical replaceable links were developed about a decade ago to improve the performance, design process, construction, and postearthquake repair process in EBFs. However, replaceable shear links are still susceptible to the commonly observed limit states in EBF links such as web fracture close to web stiffeners, local buckling, and lateral torsional buckling. This paper presents the experimental validation of a new generation of optimized cast steel replaceable yielding links for use in EBFs, which address the shortcomings of conventional and fabricated replaceable links. The performance of the proposed cast steel links is investigated through nine large-scale component-level and system-level experiments, covering a range of link sizes and loading conditions, while also studying the impact of other phenomena influencing the response such as the presence of axial load, the level of axial restraint in the links and the presence of a concrete slab. The tested series of cast links demonstrated enhanced ductility levels and low-cycle fatigue life when compared to fabricated links, achieving up to 0.21 radians of link rotation under the AISC protocol used for the qualification of EBF links.