Innovative setup and testing methodology of a nvel bidirectional rotation friction damper (BRFD)

Precast RC structures have been widely adopted for industrial and commercial buildings since the ’60s in industrially developed countries. Precast RC structures with poor connections in earthquake-prone areas have a remarkable seismic risk due to the combined effect of high seismic vulnerability and exposure. Workers’ safety requirements and the preservation of high-value facilities and stocks demand the adoption of effective retrofit techniques for earthquake risk mitigation and community resilience improvement. A novel device was patented in 2022, behaving as a frame beam-to-column joint and a damper with bidirectional dissipative capacity simultaneously. Very easy to install, low-cost and re-usable after the main shock, this Bidirectional Rotation Friction Damper (BRFD) has been designed to improve the seismic performance of such structures by excluding the brittle failure of structural and non-structural elements. Preliminary experimental tests performed at the University of Ferrara, Italy, proved the high-damping capacity of this novel device. Unlike usual dampers, the BRFD is subjected to actions in longitudinal and transversal directions and develops hysteresis cycles in both directions, making its experimental qualification peculiar. The object of this paper is the quality assessment of an ad hoc setup and testing methodology developed at the Heavy and Light Structure Lab of the University of Bristol (UK). Two orthogonal actuators have been coupled to apply displacement-force paths in two orthogonal directions. Forces, displacements and temperatures for different displacements, frequencies, and bolt preload levels were recorded. Results allowed the selection of the most appropriate testing methodology according to the expected real-use conditions for BFRDs under seismic actions.