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AISC358–16 provides seismic pre-qualification rules and design procedures for fully restrained extended stiffened end-plate bolted connections, while the cases of partially restrained connections are generally not considered for seismic applications. However, provided that the failure of both bolts and the welds is prevented, partially restrained joints may exhibit satisfactory ductile behavior, also accommodating interstory drift rotation larger than 0.04 rad. This performance can be achieved if the resistance of brittle zones of the connections is greater than the ultimate resistance of the ductile components, as experimentally proved in some recent European research projects. Therefore, the study presented in this article aims at proposing design rules for partially restrained connections in order to meet the prequalification limits given by AISC358–16. To achieve this purpose, a comprehensive parametric study based on finite element analysis (FEAs) was carried out. The numerical results show that the proposed AISC-compliant procedure can guarantee satisfactory performance of partially restrained connections, which exhibit good ductility and dissipation capacity. • AISC-compliant seismic design criteria for ductile partially-restrained end-plate bolted joints are proposed. • The effectiveness of the design criteria is verified by means of finite element analyses. • The proposed design rules guarantee ductile behavior of the connections. • The gap opening of the connection induces large membrane actions into the end-plate. • Bolts should be also designed to resist the shear forces due to the membrane effects developing in the end-plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tests to prequalify EC8-compliant extended stiffened end-plate joints are presented. • Design procedure is proposed and verified against tests and finite element simulations. • Two alternative dissipation mechanisms are promoted, i.e., full and equal strength joints. • Tests showed plastic deformations solely in the connected beam for full strength joints. • Tests showed plastic deformations in the beam and the connection for equal strength joints. An experimental and numerical campaign was carried out to validate the design procedure and prequalify extended stiffened end-plate (ESEP) joints for ductile seismic resistant moment-resisting frames in the framework of Eurocodes. In fact, the tested ESEP joints have been designed with the aim of guaranteeing ductile and dissipative seismic response in accordance with the principles of the hierarchy of resistances to enforce plastic deformations in ductile components of the joints. Two alternative types of dissipation mechanisms are promoted, namely either (i) plastic deformations solely in the connected beam using full strength joints or (ii) plastic deformations in both the beam and the connection using equal strength joints. The adopted design criteria and technological details are described and discussed. The results of experimental tests confirmed the expected yielding mechanisms of the joints, which satisfied the acceptance criteria for both North American and European prequalification. Finite element simulations of ESEP joints have been validated against the experimental results and have been used to investigate the local response of the joints, thus highlighting the influence of both geometrical and mechanical parameters. [ABSTRACT FROM AUTHOR]

The presence of rib stiffeners in extended end-plate joints influences the yield line distribution in the tensile zone of the connection, the depth of internal lever arm as well as the resistance of compression components of the joint. In addition, the stiffeners may affect the plastic rotation capacity of the connected beam in both monotonic and cyclic regime. The current EN1993:1–8 (2005) gives limited recommendations on these issues, while EN1998-1 (2005) does not provide any detailing rules to enforce ductile cyclic response when rib stiffeners are adopted in end-plate connections. In order to investigate these criticisms, extensive parametric finite element simulations were carried out and the obtained results are described and discussed in this paper. The main analyzed parameters are the thickness, the slope (i.e. the depth to width ratio), and the constructional imperfections of the rib stiffeners for different beam-to-column assemblies alternatively designed with full and partial strength connection. The monitored response from monotonic and cyclic analyses allows characterizing the yield line distribution and the variation of internal forces into the rib and the bolt rows. The evolution of the internal lever arm of the connection, the out-of-plane bending and torsional moments developing when the connected beam experiences large plastic rotations as well as the forces acting on lateral torsional restraints are also investigated. [ABSTRACT FROM AUTHOR]

Extended stiffened end-plate bolted joints are widely used in seismic resistant steel frames. In the United States of America (USA) this type of joint is seismically pre-qualified according to AISC 358-16. At the present time, prequalification criteria for different types of bolted joints are also under development in Europe within the framework of the EQUALJOINTS (i.e. European pre-QUALified steel JOINTS) research project. The design criteria and detailing rules proposed by this European project for extended stiffened end-plate joints differ from AISC criteria in some respects. Therefore, the aim of this work is to verify and to compare the effectiveness of both design procedures through the results of a comprehensive parametric study based on finite element (FE) simulations. The FE results show that both AISC and European design procedures can guarantee the formation of a plastic hinge in the beam under cyclic loading. However, under column loss scenarios the European connections are more ductile than those designed according to both AISC 358-16 and AISC 341-16. In addition, it is investigated the possibility to use heavy columns satisfying the resistance requirements without stiffeners (i.e. continuity plates and supplementary web plates). The comparison between the response of the joints with and without stiffened columns shows that heavy unstiffened columns can be adopted without appreciably modifying the joint response. [ABSTRACT FROM AUTHOR]

Bolted extended stiffened end-plate beam-to-column joints are widely used in seismic resistant steel frames. The flexural behaviour of this type of joints is crucial in order to guarantee an adequate seismic response. Eurocode 3 part 1–8 provides design rules and analytical models to predict the mechanical behaviour of the joints. Eurocode 8 provides additional design rules for seismic resistant joints, contradicting some requirements of Eurocode 3. In addition, in Eurocode 3 the influence of the rib stiffeners on the flexural response of this type of joints is not clearly accounted for. In this paper the criticisms of current versions of Eurocode 3 and Eurocode 8 are discussed and design criteria for seismic resistant extended stiffened end-plate beam-to-column joints are proposed. In addition, the results obtained from parametric finite element simulations are presented in order to support the discussion and to validate the design procedure. [ABSTRACT FROM AUTHOR]

Different types of seismic dampers are available on the market of constructions. The more effective solutions are characterized by (i) stable and predictable response, (ii) localisation of demand into the dampers minimizing the post-earthquake damage in easily replaceable parts. Friction dampers typically satisfy both requirements. These dampers are very versatile since they can be equipped in different structural arrangements. One of the most promising solutions is their application in the moment-resisting beam-to-column joints where they can effectively dissipate the seismic energy and limit plastic deformations into easily replaceable elements. Furthermore, their resistance and deformation capacity can be easily designed without interfering with the structural geometry, thus allowing the standardisation of friction connections for a wide range of beam-to-column assemblies. The current work presents a parametric study based on finite element (FE) simulations of steel beam-to-column joints equipped with a set of five predefined friction dampers specifically conceived to cover the most representative range of profiles used in Eurocode-compliant multi-storey moment resisting frames. The FE models were calibrated against recent experimental tests performed by the authors in a former study. The analyses were aimed at extending these experimental results, investigating the local behaviour of the dampers and the connections as well as the influence of member scaling on the monotonic and hysteretic behaviour of each assembly. The results confirm that the non-linear performance of connections equipped with friction dampers is almost independent on the dimensions of the connected profiles, and it is fully replicable within a predefined range of geometries [Display omitted] • A set of five predefined symmetric friction dampers was proposed for predetermined ductility and resistance. • A design chart for steel beam-to-column joints equipped with the proposed dampers was provided • The dissipative response of the examined friction joints does not depend on the size of connected members. • The flexural response of the joints equipped with the proposed dampers is not symmetric • The shear forces ìn bolted connections are significantly greater than the shear force developing in the beam. [ABSTRACT FROM AUTHOR]

Seismically pre-qualified beam-to-column joints guarantee large ductility in seismic scenarios thanks to the effectiveness of the design rules and technological requirements that are devoted to avoiding the failure of brittle components (i.e., bolts and welds). However, their performance under different severe actions like those induced by fire has not been properly investigated. Therefore, a parametric study based on finite element simulations has been carried out with the aim to verify the effectiveness of local details of seismically prequalified joints under fire. Finite element analyses were carried out on beam-to-column assemblies sub-structured from a reference archetype building accounting for both material and geometrical imperfections. The bolts' internal actions were monitored in all the investigated specimens varying the applied vertical loads. The results show that the seismic design rules adopted to size the bolts are effective to resist the large increase in shear forces in the bolts occurring under fire. Thus, the investigated joints provide satisfactory ductility and rotation capacity at high temperature preventing the failure of bolts; further analysis could be conducted to investigated the fire performance of the investigated joints in a seismic scenario. [ABSTRACT FROM AUTHOR]