Gray, Christopoulos, and Packer 2010
Steel castings have predominately been used in modern times for aesthetic appeal due to the freedom of geometry offered. Recently in the design of seismic resisting steel structures, steel castings have gained interest for the potential to simplify design and detailing of complex structural problems. The proposed cast steel connectors are designed to act as the ductile yielding fuse element in a concentrically braced frame.
System Concept
The system is designed to achieve a stable symmetric inelastic response through the flexural yielding of specially designed fingers. Unlike a BRB, the cast steel fuse is a connector that fits to the end of a standard structural shape and is intended to be readily available. The cast steel fuse is engaged by the later force resisting system during a seismic event. Energy dissipation happens through the flexural yielding of the specially designed fingers.
The fingers have been shaped to induce flexural yield along most of their length to maximize ductility. The bending and shear force diagrams of the fingers are similar in nature to a cantilever. An even distribution of plasticity occurs as the finger yields due to the nearly constant curvature along the length during deformation.
Experimental Study
A full scale prototype was designed, manufactured, and tested under cyclic, quasi-static axial loading with a universal testing machine. The prototype was created to represent the second floor brace of a 6-story steel building located in Los Angeles. Following ANSI/AISC procedures, the system was loaded based on the qualifying protocol for buckling restrained braces.
Preliminary results showed significant energy dissipation capacity. It was noted that the purely axial load test described is not a direct representation of the boundary condition of a brace in the assembly of a real building frame. The expected stiffness, strength and ductility responses of the device were confirmed by the prototype.
Reference
Gray, M. G., Christopoulos, C., Packer, J.A. (2010). “Cast Steel Yielding Fuse for Concentrically Braced Frames,” Proceedings of the 9th U.S. National and 10th Canadian Conference on Earthquake Engineering, Toronto, Ontario, Canada, July 25-29.