In this paper, the friction coefficient and the cyclic response of different interfaces for friction devices are investigated by means of experimental tests under displacement control. In particular, six interfaces have been tested: steel–steel, brass–steel, sprayed aluminum–steel and three different rubber based friction materials adopted, respectively, in automotive applications, electrical machines and applications requiring low wearing.\ud Static and kinetic friction coefficients have been evaluated and the influence of the interface pressure has been analyzed. The variation of the sliding force during the cyclic loading history has been investigated by comparing also the response coming from the use of different washers: circular flat washers and cone shaped annular disc springs.\ud The work is aimed at the investigation of friction materials to be applied within the connecting elements of beam-to-column joints according to the double split tee configuration with friction pads

In this paper, the results of an experimental program dealing with the ultimate behavior of bolted beam-to-column connections under cyclic actions are presented. The design criteria adopted for tested specimens are discussed in detail, aiming to point out how the ultimate behavior can be governed by properly strengthening the components for which yielding has to be prevented. To this scope, the component approach is adopted as a design tool for component hierarchy criteria. The aim of the paper is the investigation of the actual possibility of extending the component approach to the prediction of the cyclic response of beam-to-column joints. To this scope, the attention has been focused on the possibility to evaluate the overall energy dissipation capacity starting from the energy dissipation of the single joint components, provided that they are properly identified and their cyclic behavior is properly measured.

The sliding hinge joint (SHJ) is a type of supplemental energy dissipation system for column bases or beam-to-column connections of steel Moment Resisting Frames (MRFs). It is based on the application of symmetric/asymmetric friction dampers in joints to develop a dissipative mechanism alternative to the column/beam yielding. This typology was initially proposed in New Zealand and, more recently, is starting to be tested and applied also in Europe. While on the one hand this technology provides great benefits such as the damage avoidance, on the other hand, due to the high unloading stiffness of the dampers in tension or compression, its cyclic response is typically characterized by a limited self-centering capacity.To address this shortcoming, the objective of the work herein presented is to examine the possibility to add to these connections also a self-centering capacity proposing new layouts based on a combination of friction devices (providing energy dissipation capacity), pre-loaded threaded bars and disk springs (introducing in the joint restoring forces).In this paper, as a part of an ongoing wider experimental activity regarding the behaviour of self-centering connections, the attention is focused on the problem of achieving the selfcentering of the column bases of MRFs by studying a detail consisting in a column-splice equipped with friction dampers and threaded bars with Belleville disk springs, located above a traditional full-strength column base joint. The main benefits obtained with the proposed layout are that: i) the self-centering capability is obtained with elements (threaded bars and Belleville springs) which have a size comparable to the overall size of the column-splice cover plates; ii) all the re-centering elements are moved far from the concrete foundation avoiding any interaction with the footing. The work reports the main results of an experimental investigation and the analysis of a MRF equipped with the proposed column base joints.

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Dealing with the seismic behavior of steel MRFs, in last decade, the adoption of dissipative partialstrength beam-to-column joints has started to be considered an effective alternative to the traditional design approach which, aiming to dissipate the seismic input energy at beam ends, suggests the use of full-strength joints. On the base of past experimental results, the use of dissipative Double Split Tee (DST) connections can be considered a promising solution from the technological standpoint, because they can be easily replaced after the occurrence of a seismic event. Nevertheless, their dissipation supply under cyclic loads has been demonstrated to be characterized by significant pinching and strength degradation which undermine the energy dissipation capacity. The need to overcome these drawbacks to gain competitive technological solutions has suggested an innovative approach based on the integration of beam-to-column joints by means of friction dampers located at the beam flange level. Therefore, the use of partial strength DST joints equipped with friction pads is proposed. Aiming to the assessment of the cyclic rotational response of such innovative connections, two experimental programs have been undertaken. The first one has been aimed at characterizing the dissipative performances of five frictional interfaces to be employed as dampers. The second one is aimed at the application of the same materials to DST joints specifically designed for dissipating the seismic input energy in a couple of friction dampers located at the beam flanges level. The results of the experimental analysis carried out at the Materials and Structures Laboratory of Salerno University are herein presented, showing the potential of the proposed damage-free beam-to-column joints