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This paper is devoted to a brief presentation of the main results obtained within the FREEDAM research project. The project has been completed and, recently, also the dissemination of the results has reached the finish line. The project was devoted to the development of low-damage beam-to-column connections based on the use of friction dampers conceived to substitute the traditional dissipative zones of moment-resisting frames, i.e. the beam ends. The conception of these innovative connections is presented and the experimental tests carried out at the University of Salerno during the FREEDAM project are summarized dealing with the friction dampers, the beam-to-column joints sub-assemblages and the seismic simulation of a real scale one-bay two-storey building with the pseudo-dynamic testing method. Finally, the design procedures for seismic-resistant steel frames equipped with such connections are presented in the framework of Eurocode 8 and according to TPMC., Freedam Plus RFCS Project

The use of supplementary dissipative devices is an effective design strategy to improve the seismic response of structures. Friction devices inserted into beam-to-column joints can be a viable solution to optimize the seismic performance of steel Moment Resisting Frames (MRFs). The joints equipped with such devices are full rigid but very ductile partial strength, whose resistance can be easily calibrated to match the EC8 design moments with negligible overstrength. On the contrary, EC8-compliant MRFs equipped with traditional full-strength joints are often characterized by large beam overstrength due to the need to satisfy both serviceability and stability checks that lead largely oversizing the columns. In this paper, three design criteria for MRFs equipped with friction beam-to-column joints are described and examined by means non-linear static and dynamic analyses. The discussion of the results highlights the benefits of friction joints as well as the effectiveness of the examined design criteria.

Background:Modern seismic code design rules are known to be based on capacity design principles. They try to assure the damage to occur in the ductile parts of the structure, such as beam ends while the other have to remain in elastic range. Therefore, in the aftermath of design earthquakes, plastic deformations at member or connection level will imply high repair costs. In the last decades, innovative structural solutions based on the so-called supplementary energy dissipation strategy allow increasing the dissipative capacity of structures through equipping it with special damping devices. In the case of substitution of dissipative zones with dissipative devices the strategy takes the name of substitutive strategy. This is the case of Moment Resisting Frames investigated in this paper, where traditional dissipa-tive zones, are equipped with innovative low damage frictional devices. However, the current version of codes does not provide any rules to design of MRFs equipped with this type of friction joints.Methods:Therefore, this paper reports two design approaches amply investigated and compared. The first one is based on the application of the Beam-to-Column Hierarchy Criterion (BCHC) while the second one exploits the Theory of Plastic Mechanism Control (TPMC). The comparison between them is herein discussed on the basis of the results of nonlinear static and dynamic analyses.Conclusions:Structures equipped with low damage frictional connections show larger drift demand than conventional Moment Resisting Frames. However, differently from traditional structures, the larger displacement demand of MRFs equipped with friction joints does not corre-spond to structural damage, thus allowing the reparability of the structure.