Design considerations for shear links in eccentrically braced frames

Eccentrically braced framing has been gaining acceptance in seismic applications because this system can provide both high elastic stiffness and large energy dissipation capacity. The performance cf an eccentrically braced frame depends to a great extent on the behavior of short beam segments called active links. Through bending and shear. active links transfer the axial forces in the diagonal braces to other braces or to columns. These short beam members provide the primary energy dissipation mechanism for properly designed eccentrically braced frames. The results of previous experimental and analytical research has provided a good deal of information on the cyclic behavior of active links. This work has demonstrated that short active links which yield in shear (shear links) can dissipate more energy than longer active links which yield primarily in bending (bending links). However. some aspects critical to the economical design of an eccentrically braced frame which employs shear links have yet to be addressed. includina the sensitivity of link behavior to the imposed loading history. ttte linkcolumn connection detail. and the web stiffener desip and details. These three important considerations of shear link behavior are discussed in this report. The results of twelve full size shear link specimens are presented. Fach of the specimens was designed 10 investigate specific shear link response characteristics. Four specimens were tested with stiffener details which differed sisnificantly from those of previous experiments and early design applications. Another set of four specimens were designed and te~led wilh wid~ly varyina loadins histories. A set of four specimens which employed conventional moment resis~­ iog connection details were also tested. The qualitative and quantitative results of these experiments were compared and analyzed usina enel'lY dissipation capacity as a mlijor parameter. Test conclusions and desian recommendations lenerated by the lest results are then presented.