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Industrial single-storey buildings are the most diffuse typology of steel construction located in Italy. Most of these existing buildings were erected prior to the enforcement of adequate seismic provisions; hence, crucial attention is paid nowadays to the design of low-impact retrofit interventions which can restore a proper structural performance without interrupting productive activities. Within this framework, an existing industrial single-storey steel building located in Nusco (Italy) is selected in this paper as a case-study. The structure, which features moment resisting (MR) truss frames in both directions, is highly deformable and presents undersized MR bolted connections. Structural performance of the case-study was assessed by means of both global and local refined numerical analyses. As expected, the inadequate performance of connections, which fail due to brittle mechanisms, detrimentally affects the global response of the structure both in terms of lateral stiffness and resistance. This effect was accounted for in global analyses by means of properly calibrated non-linear links. Thus, both local and global retrofit interventions were designed and numerically investigated. Namely, lower chord connections were strengthened by means of rib stiffeners and additional rows of M20 10.9 bolts, whereas concentrically braced frames (CBFs) were placed on both directions' facades. Designed interventions proved to be effective for the full structural retrofitting against both seismic and wind actions without limiting building accessibility. [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]