Experimental Investigation of a Combined System in Steel Braced Frames

In general, the analysis and design of buildings must satisfy two criteria. First, under frequently occurring low to moderate earthquakes, the structure should have sufficient strength and stiffness to control deflection and to prevent any structural damage. Second, under rare, severe earthquakes, the structure must have sufficient ductility to prevent collapse. In this case, significant damage to the structure and nonstructural elements is acceptable. In this paper, the performance of an innovative, eccentric and knee bracing system called Eccentrically Knee Brace (EKB) is discussed and the behavior is investigated. A combination of eccentrically braced steel frames and knee braced steel frames has been assessed, and the concepts of the design of defined schemes are reviewed. As the structural fuse of the frame, the knee element will yield first during a moderate earthquake. In large earthquakes, both of them contribute in dissipating energy. Two half-scale EKBs were tested using the SAC loading protocol and an innovative loading protocol. The performance evaluation procedure includes laboratory and computer simulations. Cyclic loading tests were conducted to study the behavior of EKB.