Month: June 2022

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This paper is devoted to a brief presentation of the main results obtained within the FREEDAM research project. The project has been completed and, recently, also the dissemination of the results has reached the finish line. The project was devoted to the development of low-damage beam-to-column connections based on the use of friction dampers conceived to substitute the traditional dissipative zones of moment-resisting frames, i.e. the beam ends. The conception of these innovative connections is presented and the experimental tests carried out at the University of Salerno during the FREEDAM project are summarized dealing with the friction dampers, the beam-to-column joints sub-assemblages and the seismic simulation of a real scale one-bay two-storey building with the pseudo-dynamic testing method. Finally, the design procedures for seismic-resistant steel frames equipped with such connections are presented in the framework of Eurocode 8 and according to TPMC.

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FREEDAM connections consist of a symmetric friction device connecting the lower flange of the beam to the column by means of L-Stubs. This assembly prevents the damage of the connected members and dissipates energy by means of the slippage between the clamped steel elements and the friction pads of the device. In order to characterize the monotonic and cyclic performance of the joints equipped with friction dampers a comprehensive and extensive parametric finite element (FE) simulations have been carried. The FE models have been validated against the experimental results of the tests carried out within the FREEDAM project. The performed FE analyses allowed evaluating the response of both external and internal joints with the FREEDAM devices. In addition, different geometries of the friction dampers and the relevant beam-column assemblies have been investigated. The FE analyses confirmed the effectiveness of the design assumptions and the satisfactory performance of the investigated joints

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The high seismic performance of steel frame structures equipped with FREEDAM dissipative joints has been demonstrated through experimental and extensive numerical studies in the framework of a recent RFCS project. In particular, the performance of moment-resisting frames (MRFs) and dual concentrically braced frames (D-CBFs) was thoroughly investigated under seismic actions. Although the research has shown that such structures can dissipate the earthquake-induced energy with limited or even no damage, their robustness in case of accidental actions was not yet addressed. Hence, as required by the current version of Eurocodes, their ability to survive accidental events should be demonstrated. This paper presents the robustness assessment performed on 20 MRFs and D-CBFs under a Eurocode-compliant column loss scenario. In addition, analytical and numerical studies were conducted to demonstrate how the request for robustness influences the design of the joints initially tailored for seismic performances.

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In this work, the efficiency of four passive energy dissipation means, including viscous, viscoelastic, friction, and metallic yielding dampers, in high-rise building response was evaluated and compared. Conventional analyses and designs generally neglect the effects of soil and foundation flexibility. This effect is also considered in this study. First, a 20-story building with a steel moment frame was considered. Then, the nonlinear 2D model of this building is developed and subjected to nonlinear static pushover analysis to identify the floors that need a damper. The Response Reduction Theory method is used for this purpose. After designing each damper, four different models were replicated using viscous, frictional, metallic, and viscoelastic dampers. Each model was subjected to nonlinear dynamic analysis using ten far-fault ground motion records. The structural responses were extracted in the uncontrolled condition and in four controlled conditions with dampers. The results show that the metallic yielding and viscoelastic dampers have the best performance in reducing the structural responses than viscous and frictional dampers.

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