Rai and Wallace 1998
The paper reviews a study of aluminium shears-links used with structural lateral resistance frames. Aluminium was selected as the link material due to its low yield strength. The link was designed to yield in shear mode and limit the maximum lateral force which would be transmitted to primary structural members. This link also provided significant energy-dissipation. The paper describes the behavior of the shear-link and its role in the structural system through experimental results and a numerical assessment of its seismic performance.
System Concept
Aluminium was chosen because of its low yield strength and its ability to last through many large plastic deformation cycles before tearing. In shear modes, it can reach greater ductility and dissipate significant amounts of energy. One application of the shear-link is to retrofit chevron-type ordinary CBF. An. The link-beam is designed to yield in shear mode at a lateral force less than that required to buckle the brace in compression. An advantage of this system is that it can carry gravity loads after the link collapse.
Experimental Study, Results, and Discussion
A medium scale of 1:4 was chosen for the experimental testing. The specimens varied in section dimensions, two different alloys of aluminium (3003 and 6061), and arrangements of transverse stiffeners. The purpose of the stiffeners was to delay the initiation of plastic web buckling and improve post-buckling behavior. The specimens were loaded using a sinusoidal input wave with both stress and strain controlled regimes during the experimental testing. The links demonstrated excellent stiffness and energy dissipative capacity over a large range of strains. The softer alloy 3003 is favored due to its better energy dissipation characteristics.
A model of a 4-story building located in the UBC Seismic Zone 4 was created using SNAP-2D. A shear-link braced frame was compared to an ordinary CBF under a static push over analysis and four different ground motions of record. The static push over analysis showed the shear-link braced frame was able to resist additional shear force through a larger deformation as opposed to the ordinary CBF which reduced capacity after brace buckling. The results of the monotonic loading show a reduced base shear, more uniform distribution of story drifts and a larger energy dissipation capacity per unit drift when comparing the shear-link braced frame to the ordinary CBF.
Reference
Rai, D. C. and Wallace, B. J. (1998). “Aluminium Shear-Links for Enhanced Seismic Resistance,” Earthquake Engineering and Structural Dynamics 27, 315-342 (1998).