Replaceable friction device for steel-concrete composite trussed beam-to-RC column joint

During the last years, earthquake-resilient Moment-Resisting Frames (MRFs) structures have become increasingly popular thanks to their ability of limiting the damage experienced by surrounding structural and non-structural members. Within this framework, few solutions have been proposed for cast-in-situ steel-concrete composite structures, being challenging to develop earthquake- proof low-cost beam-to-column connections. This issue can be solved by using the structural typology of the Hybrid Steel-Trussed Concrete Beams (HSTCB). These are usually design to cover long spans with a small height, leading to a large amount of rebars, which, passing through small beam-column joints, make the latter more easily damageable if subjected to an earthquake. The introduction of friction devices at the Beam-to-Column Connections (BCCs) can help to lengthen the lever arm of the moment transferred between beam and column, thus decreasing the shear force acting on the RC joint preventing its damage. In this context, this paper focuses on a new BCC developed for RC MRFs made with HSTCBs, which is endowed with a replaceable friction device. The main features of the proposed solution and its design procedure are outlined. After that, a comprehensive 3D finite element model of the proposed solution is developed. Monotonic and cyclic analyses are carried out considering several sliding moment values. The results prove that the proposed connection is able not only to provide adequate dissipative capacity, but also to avoid damaging of surrounding RC members.