Seismic retrofit of reinforced concrete soft-storey structures using toggle-brace-damper system

This paper presents a seismic retrofit method to reinforced concrete structures which suffer from soft-storey mechanism in their ground level. The proposed method consists of strengthening of columns by FRP wraps, and an inclusion of a double, upper toggle-brace-damper system. This method considers functionality and practicality in retrofits of existing structures. Governing equations are examined. It is found that, if designed properly the toggle-brace-damper significantly increases stiffness and effective damping of system.The complete system can be described by a simple, nonlinear single-degree-of-freedom system.