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Within European Research Project “FREEDAM” supported by RFCS a design procedure for MRFs equipped with friction dampers has been developed. In particular, beam-to-column joints are equipped with friction dampers located at the bottom flange level namely “FREEDAM” dampers. Therefore, all the connections are conceived in order to prevent structural damage. A prototype structure has been designed according to a design procedure assuring a collapse mechanism of global type whose name is Theory of Plastic Mechanism Control, and its seismic performances have been investigated by means of IDA analyses in a companion paper.

The work herein presented is devoted to the validation of TPMC design procedure applied to steel MRFs equipped with FREEDAM dampers located at beam-to-column joints. The seismic performances evaluations of the designed structure have been carried out by means of both Push-over analysis and Incremental Dynamic Analysis. In particular, the Push-over analysis aims to confirm the real development of a collapse mechanism of global type, while, through IDA analysis, Maximum Interstorey Drift and Top Residual Displacement performed by the designed structures have been pointed out. For this reason, a MRF whose design procedure by TPMC is detailed in a companion paper has been subjected to both push-over and IDA analysis.

The slab plays an important role in seismic response of reinforced concrete (RC) Structures because it allows to actively distribute the seismic actions among all the resistant primary elements. However, its contribution cannot be relegated to simple rigid diaphragm but its capacity of increasing strength and stiffness in beam-to-column joints must be considered. Although some experimental campaign were performed to prove that the slab contribution in terms of resistance cannot be neglected, the current seismic European code (Eurocode 8) does not provide a proper formulation to estimate the actual contribution of the slab in terms of strength and stiffness on the seismic response of RC buildings. To this scope, in the present work, an experimental campaign on six RC beam-to-column joints with and without floor slab were carried out by performing both monotonic and cyclic tests. The main research goal is the validation through an experimental evidence of the effectiveness of the theoretical formulations proposed in previous works, able to evaluate the deck contribution in the beam-to-column joint resistance. In particular, reference is made to RC joists with upper slab and interlaid tiles monolithically cast with the beams, which is a constructive typology largely spread in the Mediterranean area.

The work hereinafter discussed concerns the evaluation of the seismic performances of a traditional Moment Resisting Frame and a Moment Resisting Frame equipped with friction dampers, called “FREEDAM”. A multi-records IDA analysis has been performed and the results have been evaluated in terms of interstorey drift for each storey.

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.

The work herein presented concerns the modelling of a Moment Resisting steel frame within SeismoStruct computer program. In particular, it focuses on how it is possible to take into account the second order effects, structure effects, in order to best reproduce the real structure behaviour. It is well known a way to consider second-order effects on a frame is add a leaning column to this one. But how leaning column may be modelled and how it influences the results of frame analysis?

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.