Post-Northridge connections with slit dampers to enhance strength and ductility

In 1994 and 1995, Northridge and Kobe earthquakes caused unexpected damages to beam-to-column connections which were followed by extensive investigations on the connections' behavior to resolve problems in their performance and to improve their strength and ductility. During these years methods were proposed by researchers which were mainly based on reducing the beam section or strengthening the connection. Adding slit dampers at the top and bottom of the beam flanges plates is another way to improve the connection behavior. These dampers are able to absorb and dissipate a significant amount of energy. Slit dampers caused a remarkable reduction in the plastic strain at the column face area and consequently kept plastic hinge formation away from the column face. In this study a total of 8 small slit dampers were used at the column face area. To find out best configuration for slit dampers which can only be used for newly designed connections, a parametric study was carried on their geometry. Generally the slit damper yields in shear or in flexure. Hence, for two different yield mechanisms (shear yielding and flexural yielding) details for designing of slit dampers were proposed and connection's strength and ductility were compared.