ECCENTRICALLY KNEE BRACING: IMPROVEMENT IN SEISMIC DESIGN AND BEHAVIOR OF STEEL FRAMES

The use of passive control systems is widely considered as a reliable approach for controlling earthquake vibrations in steel structures. First, under frequently occurring low to moderate earthquakes, the structure should have sufficient strength and stiffness to control deflection and prevent any structural damage. Second, under rare and severe earthquakes, the structure must have sufficient ductility to prevent collapse. For this case, significant damage of the structure and nonstructural elements is acceptable. In this paper, the performance of a new innovative eccentrically and knee bracing system called Eccentrically Knee Bracing (EKB) is discussed and the behavior is investigated. A combination of eccentrically braced steel frames and knee braced steel frame has been assessed and 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 EKB were tested using the SAC loading protocol and an innovate loading protocol.