Mansour, Christopoulo, and Tremblay 2011
An Eccentrically Braced Frame (EBF) is designed for seismic lateral load resistance. A section of the beam elements within the frame are ductile in behavior in order to dissipate energy. Current design involves implementing the ductile link as part of the floor beam, causing an overdesign of the beam. This drawback is addressed by creating a replaceable yield link which is decoupled from the structural element. The concentrated inelastic deformation in the link can be inspected and replaced following major seismic events.
System Concept
The research focused on two types of replaceable link configurations. The first is fabricated from a W-section welded to unstiffened end plates. These places are bolted to the floor beam end plates. The second link is an assembly of two channel sections, back-to-back, connected to the floor beam through the web. The connection can be either bolted or welded. The specimens of interested were considered to be at the second floor of a 5-story EBF.
Experimental Study, Results, and Discussion
Link component test were conducted in order to verify that the links were able to achieve a ductility capacity of 0.08 rad plastic link rotation. The specimens were subjected to a constant shear force along their length, equal reverse curvature bending moments at the ends, and no axial force. It was shown that the replaceable links were able to exceed the required ductility capacity.
In order to assess the global performance of the EBF with replaceable links, a second experimental testing program was executed. A test frame representing the first story of a 5-story EBR was assembled with the replaceable link. Lateral load was applied to the floor beam through two actuators reaction onto the strong wall. Cyclic shear deformations were imposed on the frame.
When the test specimens were compared to a bare steel link, it was found that the transfer of shear was 14% greater. It was also noted that the presence of a composite concrete slab did not restrain the link from achieving large shear deformations. Replaceability of the link sections was confirmed, even with residual deformations of 0.5% drift with bolted and welded web connections.
Reference
Mansour, N., Christopoulos, C., and Tremblay, R. (2011). ”Experimental Validation of Replaceable Shear Links for Eccentrically Braced Steel Frames.” Journal of Structural Engineering, 137.10, pp. 1141–1152.