Influence of connection typology on seismic response of MR-Frames with and without ‘set-backs’

The work presented is aimed at the investigation of the influence of beam-to-column connections on the seismic response of MR-Frames, with and without ‘set-backs’, designed according to the Theory of Plastic Mechanism Control. The investigated connection typologies are four partial strength connections whose structural details have been designed to obtain the same flexural resistance. The first three joints are designed by means of hierarchy criteria based on the component approach and are characterized by different location of the weakest joint component, leading to different values of joint rotational stiffness and plastic rotation supply and affecting the shape of the hysteresis loops governing the dissipative capacity. The last typology is a beam-to-column connection equipped with friction pads devoted to the dissipation of the earthquake input energy, thus preventing the connection damage. An appropriate modelling is needed to accurately represent both strength and deformation characteristics, especially with reference to partial-strength connections where the dissipation of the earthquake input energy occurs. To this aim, beam-to-column joints are modelled by means of rotational inelastic springs located at the ends of the beams whose moment-rotation curve is characterized by a cyclic behaviour which accounts for stiffness and strength degradation and pinching phenomena. The parameters characterizing the cyclic hysteretic behaviour have been calibrated on the base of experimental results aiming to the best fitting. Successively, the prediction of the structural response of MR-Frames, both regular frames and frames with set-backs, equipped with such connections has been carried out by means of both push-over and Incremental Dynamic Analyses. Copyright © 2016 John Wiley & Sons, Ltd.