Fuse performance on bracing of concentrically steel braced frames under cyclic loading

• Development of ductile fuse system for concentrically steel angle braced frame
• Performance evaluation of ductile fuses in braced frame subjected to cyclic loading
• Recommendations are made for efficient fuse patterns for practical design.

This paper describes the development of ductile fuse system for steel angle bracings to reduce the seismic demand to the connections of concentrically braced frames. In such type of structure, the connections often need reinforcement to resist the tensile capacity of the bracing to comply with the capacity design procedure recommended by most design codes. In this research, various models of ductile fuses consisting of smoothly reduced angle section are placed on the X-bracing of a braced frame. The fuses are designed to reduce the tensile capacity of braced members to the capacity of the bolted connections. To evaluate the performance of the fuse system, two different thicknesses of single angle members with leg width of 64 mm part of an X-bracing are tested cyclically in a 1.75-m high frame representing a building story. It was observed that the braced frame with fuse could be used to reduce seismic load demand to the connections sufficiently to avoid connection strengthening that would result from the application of the capacity design principles. It was observed that properly designed fuse system in braced frame showed stable hysteretic response under cyclic loading and maintained adequate ductility with a reasonable compromise on the compressive strength of braced members. Finally, based on the study results, most efficient fuse patterns are identified for practical design applications.