Comparison between different design strategies for freedam frames: Push-overs and IDA analyses

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 dissipative 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 correspond to structural damage, thus allowing the reparability of the structure.