Improving seismic performance of non-ductile reinforced concrete frames through the combined behavior of friction and metallic dampers

This paper describes a seismic strengthening technique using a wall-type damping system (DS), targeted at moment-resisting frame buildings. The DS under consideration is a hybrid damper which works through the combined and multi-phase action of a friction damper (FD) and a metallic damper (MD). To assess the seismic effectiveness of the proposed system, full-scale cyclic tests were conducted on a bare reinforced concrete (RC) frame with non-ductile detailing and four damper-strengthened frames. The RC frame showed highly pinched behavior, whereas the hysteresis curves of strengthened frames were more stable due to the activation of FD and/or MD, forming a larger loop area. The deformation capacities of the RC frame and strengthened frames were not significantly different, but the maximum strength, stiffness, and energy dissipation capacities were significantly improved in the strengthened frames. The calculated strength and stiffness equations accurately represented the actual behavior of the RC frame. Conversely, the stiffness values of the DS were considerably lower than predicted by theoretical equations as a result of the softening of anchorage fixity according to the connection details.