Utilizing I‐shaped shear links as dampers to improve the behavior of concentrically braced frames

Abstract

SummaryDuring the past few decades, concentrically braced frames (CBFs) have become a commonly used load‐resistant bearing system in steel structures, to overcome the post‐earthquake performance issues frequently associated with conventional seismic‐resisting structural systems. CBF systems have high lateral stiffness and lateral strength; however, they have low ductility and a low seismic energy dissipating capacity. Under seismic loading, the diagonal members of a CBF system are susceptible to buckling, causing hysteresis in the compression zone and severely reducing energy absorption. Although the use of steel dampers to enhance the behavior of CBF systems can prevent the buckling of CBF members and improve the hysteretic behavior of braces, their use imposes additional costs on structures. Therefore, in this paper, an I‐shaped steel damper with a shear yield mechanism is introduced which is economical, has a simple construction, and can be easily replaced after an earthquake. The proposed damper is evaluated numerically and parametrically. The results indicate that the proposed damper acts as a ductile fuse that prevents buckling of the diagonal members of a CBF system. It was found that both the web and flange plates contribute to the shear resistance, with the flange carrying approximately 15% of the shear force, as expressed in the equations presented. The overstrength obtained for the damper was found to be greater than the value of 1.5 proposed by the AISC. Equations are presented for the design of the proposed damper and the brace elements connected to the damper.