Dissipative braces based on high damping rubber: analysis and design

Viscoelastic devices have proven to be very efficient devices for new buildings and seismic retrofitting of existing structures. They are usually obtained by using copolymers or glassy substances, though recently High Damping Rubber (HDR), already used in vibration or seismic isolators, has also been employed. The behaviour of HDR is quite complex and both stiffness and damping devices significantly depend on the strain amplitude and strain rate. Equivalent linear models may however be used to simulate their behaviour at a fixed displacement amplitude and frequency, with an acceptable approximation level. This paper proposes a design method for dissipating braces inserted in reinforced concrete (r.c.) frames with limited ductility. The dissipative behaviour of both the two components (r.c. frame and HDR dampers) are taken into account, by considering an equivalent linear model for HDR-based devices and an equivalent viscous damping coefficient for the r.c. frame to allow for its hysteretic behaviour.