A Novel Friction Damper for Seismic Retrofit of Precast RC Structures with Poor Connections

Precast RC structures are commonly adopted for industrial and commercial buildings, to build huge spaces with limited costs and construction times. Due to the lack of efficient seismic regulations until recent times, and adequate assessments of seismic hazard, a huge number of seismically inadequate precast RC buildings are spread through Southern Europe territories. Workers’ and users’ safety requirements, and the preservation of high-value facilities and stocks, demand the adoption of effective retrofit techniques for earthquake risk mitigation. For this structural typology, connections between structural elements are often crucial for carrying lateral loads, such as earthquakes. This study presents an innovative device that acts as beam-to-column joint and as damper at once, with bidirectional dissipative capacity. Very easy to install, low cost and reusable after the main shock, this novel Bidirectional Rotation Friction Damper (BRFD) has been conceptualized and 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, have proved the high-damping capacity of this novel device. BRFD effectiveness on a precast structure has been explored using nonlinear time-history analysis accounting both low- and high-intensity Italian earthquakes. Numerical modelling has shown that no beam’s slippage on column top section and no column crisis can occur in both building directions when BRFD are properly implemented. The designed devices provide a global improvement of the seismic performance of the building, preventing any structural and non-structural damage even for the more critical Near-Field events.