Experimental and numerical study of a motion amplification mechanism to enhance the seismic energy-dissipation capacity of precast, post-tensioned concrete rocking systems

This paper describes research on the behavior of precast, post-tensioned concrete rocking systems with a proposed new type of external rotational friction damper. The proposed damper takes advantage of geometrical arrangement with small initial angle (less than 20 degrees) to amplify the relative rotations due to the unique gap opening mechanism that occurs in the joints of these systems. These relative rotations, which take place on friction surfaces between metallic friction plates, contribute to the energy dissipation and force capacity of the system by means of rotational friction. The novelty of the proposed damper stems from the amplification effect, which provides substantial energy dissipation capacity even in small drift demands. In this study, a numerical model was developed and verified with experimental results. This numerical model was used to analyze unbonded, post-tensioned beam-column subassemblies and frames with and without the proposed damper tested to develop the force-displacement relations. The analysis results indicate that the proposed damper would effectively dissipate seismic energy and increase force capacity.