Abstract. The most recent design strategies are welcoming the adoption of sustainable innovative techniques for the seismic energy input mitigation, with the aim of achieving high dissipation capacity and preventing the structure from collapse, for the safeguard of human lives and with the scope of ensuring the serviceability of the construction. Friction damper devices are widely studied and adopted in framed steel structures since decades, while their introduction in different structural types is still under investigation. This paper presents the outcomes of an innovative research supported by the industry and conducted on beam-to-column connections of RC structures in which the beams are Hybrid Steel-Trussed Concrete Beams (HSTCBs) and the columns are classical RC pillars. An innovative solution, recently patented, has been found for the mitigation of the effects of seismic cyclic actions on small-sized beam-column joints, typically characterized by a large amount of longitudinal reinforcement due to the small effective depth of the beam. The innovative research started from the observation that HSTCBs are endowed with a bottom steel plate and, therefore, they are similar to structural steel members that can be easily endowed with a friction device. This paper collects the main featuring steps of the innovative research, which has led to the patented solution. The calculation procedure used for the design of the proposed connection is shown and the validation through 3D finite element modelling is described. For the structural analysis of the joint, several monotonic and cyclic simulations have been carried out with the scope of investigating different design moment values. The finite element results proved that the patented solution is effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by a flexural behaviour dominated by wide and stable hysteresis loops.

Keywords: Friction dampers; Hybrid steel-trussed-concrete beams; RC joints; Finite element models; Earthquake design.