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Fatigue performance is often a key aspect when dealing with existing steel structures such as steel bridges or offshore constructions. This issue proves to be more critical as these structures are usually located in aggressive environments and are thus exposed to progressive degradation. Indeed, disruptive phenomena such as corrosion can severely worsen the fatigue performance of the steel components. Currently, the normative standards do not provide a codified procedure for the fatigue checks of steel structures subjected to ongoing corrosion. Within this framework, in this paper a simplified approach for the life-cycle assessment of corroded steel structures is proposed. For this purpose, the concept of “critical corrosion degree” is introduced, allowing the expression of corrosion fatigue checks in a more direct “demand vs. capacity” form with respect to the currently available methods. A first validation of such methodology is reported for the corrosion fatigue tests drawn from the literature. The predicted levels of critical corrosion are in good agreement with the values of artificially induced corrosion (i.e., 4, 8, and 12% of mass loss, respectively), with a maximum relative error of ≈9.3% for the most corroded specimen. Finally, parametrical analyses are performed, highlighting the influence of the model parameters on the corrosion fatigue performance of the steel elements.

Nowadays, the development of rapid and low-impact structural rehabilitation strategies and techniques is very topical. These prerogatives are essential for the seismic retrofit of industrial buildings, for which the seismic retrofit solution should be selected also accounting for the impact of the interventions on the productive activities. Therefore, a retrofit solution that allows to increase the structural capacity without interfering with the industries production could be preferred with respect to canonical retrofit solutions. In this framework, the aim of the present work is to investigate the efficiency of orthogonal steel exoskeletons for the retrofitting of a steel single-storey industrial building. The investigated case study has poor lateral stiffness and strength. Following a specific design methodology, the various elements of the system were designed, and their efficiency was assessed by means of a non-linear static procedure. Moreover, a local retrofit of the truss to column connections of the MFRs was performed and investigated by means of FEM analysis.

The present work is focused on seismic assessment and retrofit of the beam-to-column joints of an existing non-conforming steel building. Refined finite element analyses were performed to investigate the performance of the existing beam-to-column joints under monotonic and cyclic loading conditions as well as the effectiveness of different strengthening interventions. The main features of these joints are the continuity of beams and hollow square columns interrupted at each level and connected by a bolted flange that is strengthened by fillet welds to the tapered flanges of the beams. The results of the finite element simulations show that the existing joints of the examined building exhibit very poor seismic behaviour, mainly due to failure of the welds. On the contrary, the strengthened joints have enhanced response. The comparison between the response of the unreinforced and the various retrofitted joints is described, and the best solutions in terms of both cyclic behaviour and technological feasibility are subsequently identified.

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.