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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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Several researchers propose placing diagonal reinforcing bars at the base of the wall to treat the shear slip, while others have suggested various ways to address this problem associated with halting the effects incurred by the through-crack in the base of the wall during cyclic loading. An indicative proposal of the bibliography is the use of large diameter reinforcement bars in the web of the wall as vertical reinforcements, so as to be able to better control the shear action through the dowel action of these bars. The two aforementioned proposals, while adequately addressing the phenomenon of shear slip, present significant disadvantages. The use of diagonal reinforcement is very difficult to construct, because of the density of the existing reinforcement in the base of the walls, which involves compromising good concrete condensation. Also, the use of large diameter vertical reinforcement along the length of the whole wall section, including its web, is a strongly uneconomical solution. This work examines a solution without the aforementioned side-effects. The innovation of the present work is the fact that it positions stoppers in combination with the use of conventional reinforcing bars at positions in the critical zones of the walls, in order to prevent the expected slip along the through-crack in the base of the rigidly supported wall. The work is experimental and includes two stages. The first stage was carried out with the construction of six test specimens, which can be considered as preliminary base specimens used for a first examination of the mechanical behavior of the walls with integrated steel hollow beams at their ends. These test results are a prelude to the second stage of the present study, including the experimental investigation of the seismic mechanical properties of a wall specimen, detailed either with conventional reinforcement according to EC8 or with the same conventional reinforcement but including also steel hollow beams at its confined edges.

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The paper is focused on the seismic performance of steel storage pallet racks, which represent a very competitive solution, widely used to store goods and materials. In particular, the design strategy herein proposed is based on a procedure which directly correlate the static and the seismic rack performance using the so-called Incremental Dynamic Analysis (IDA) approach. Despite this approach is a well-established analysis method, generally used for defining the risk associated with seismic events, it is rarely employed in the routine design of steel racks. In fact, independently of the complexity of the racks under investigation, only the modal response spectrum analysis (MRSA) is usually adopted, neglecting hence some non-negligible peculiarities of these structures. This is mainly due to the lack of time during the design phases.
The proposed procedure, named QUSDRA (QUick Seismic Design of steel storage RAcks), allows designers to choose the more convenient structural solution by considering both costs and the key structural performance parameters (i.e. reduction of the load carrying capacity, transient interstorey drift and residual interstorey drift), with limited computational efforts. In fact, QUSDRA method is directly based on an IDA database which, once created, can be used for the rack design on different seismic area.
In order to better understand the key phases of the procedure, a step-by-step case study is presented, highlighting the main advantages associated with the proposed approach.

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In order to study the seismic performance of corroded steel frame structures in sulfate environment, outdoor accelerated corrosion tests and lateral low cyclic loading tests were carried out on six plane steel frame structures. Firstly, a deterioration model of mechanical property with mass loss rate for corroded Q235B steel was proposed. Then, the failure process and characteristics of corroded plane steel frame structures were observed, the effects of corrosion level and axial compression ratio on the hysteretic curves, bearing capacity, stiffness degradation, ductility and energy dissipation capacity were studied in detail. The test results indicated that in relatively slight corrosion level, all specimens exhibited a hybrid yield dissipation mechanism. However, an increase in corrosion level tended to accelerate plastic hinge formation and aggravate structural damage degree. Additionally, with the increase of corrosion level, the lateral bearing capacity reduced, stiffness degradation intensified, ductility and energy dissipation capacity decreased; with the increase of axial compression ratio, the ultimate bearing capacity, ductility and energy dissipation all decreased.

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The use of high strength (HS) steel in seismic applications is very attractive due to economical and mechanical benefits. The combined use of HSS for non-dissipative members and MCS for dissipative zones is generally termed “dual-steel” concept and it could likely represent a valuable aid to satisfy capacity design criteria and to control the global frame behaviour, even contemporarily reducing the constructional cost. The current paper investigates the benefits of applying dual-steel concept to the seismic design of eccentrically braced frames equipped with short links in the framework of EN 1998-1:2005. With this purpose, a comprehensive numerical parametric study has been carried out: both static and dynamic nonlinear analyses have been performed to investigate the advantages of using HSS to enhance strength and ductility of a set of mid- and high-rise simple and dual eccentrically braced frames.  

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