Experimental investigation of steel frames with single bays of symmetrical y-shaped concentric bracings

To obtain wider openings than those provided by chevron bracing, the braces are crankedand connected to the frame corner by an additional brace to form double y-shaped bracings. however,y-bracings are prone to instability and out of plane buckling, accompanied by low hysteretic energyabsorption. an experimental research program, focused on y-bracing, was conducted at the bhrcstructural engineering laboratory. specimens presented in this paper include three full-scale single bayframes, with symmetric y-bracing of different cross sections and connection types. in addition, onespecimen with chevron bracing was tested as a reference. a quasi-static cyclic loading was appliedincreasingly until yielding and failure occurred in the specimens. the results show that out-of-planebuckling is the governing mode of behavior, despite differences in the detailing of cross sections andconnections. hysteretic energy dissipation and damping of y-bracing are remarkably improved due to theflexural deformation of brace members. the seismic performance of the three y-braced frame specimensand a reference chevron-braced frame was assessed using the capacity spectrum method. the resultsshow that the y-braced frame, with double gusset plates, can carry almost 60% more weight than y-bracedframes with single gusset plates.