Type testing of Bidirectional Rotational Friction Dampers (BRFD) for seismic retrofit of precast RC structures

Precast reinforced concrete (RC) structures have been widely adopted for industrial and commercial buildings since the 1960s, particularly in economically developed regions. However, during those decades of rapid growth, most buildings were designed for gravity loads only, without seismic provisions. Consequently, this structural typology presents significant seismic vulnerability in earthquake-prone areas, primarily due to weak or ineffective connections between structural elements. Retrofitting precast RC structures is therefore essential to extend their service life and reduce seismic risk. To address this challenge, a novel device called the Bidirectional Rotational Friction Damper (BRFD) has been developed for the seismic retrofit of precast RC buildings. Acting simultaneously as a beam-to-column joint and an energy dissipation system, the BRFD combines the principles of rotational friction dampers with a movable plate mechanism, providing damping in two orthogonal directions. Its friction-based energy dissipation mechanism ensures durability and stable performance over multiple seismic events, without loss of damping capacity. This paper presents the type-testing of the BRFD, conducted in accordance with EN 15129 guidelines. The experimental campaign was carried out at the Department of Engineering, University of Ferrara, using a bespoke bidirectional setup to replicate realistic working conditions. Tests applied increasing displacement amplitudes and frequencies along both principal directions of the BRFD. Two prototypes, incorporating two different friction interfaces, were investigated. The results demonstrated consistent hysteretic behaviour, high and stable damping capacity, and negligible temperature dependence, even after several loading cycles.