New expressions to estimate damping in direct displacement baseddesign for special concentrically-braced frames

Different expressions have been developed to determine damping of structures based on various hysteretic models and ductility levels. Since Slenderness ratio is an important parameter on the hysteretic behavior of special concentrically- braced frames (SCBF), in this paper new expressions for determination of damping of such frames are developed based on slenderness ratio and ductility. Two types of SCBF are considered: Inverted V braced frame and X braced frame. Using Jacobsen method, damping is determined and then modified by means of nonlinear time history analysis for special inverted V and X braced frames. A simplified methodology is proposed by using revised effective mass to modify the hysteretic damping. Using the simplified methodology, expressions are proposed to estimate damping for special concentrically- braced frames.