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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.

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.