Contents lists available at ScienceDirect Journal of Building Engineering journal homepage: www.elsevier.com/locate/jobe Versatility of steel in correcting construction deficiencies and in seismic retrofitting of RC buildings Paolo Foraboschi Università IUAV di Venezia, Dipartimento Architettura Costruzione Conservazione, Dorsoduro 2206, 30123 Venezia, Italy ARTICLE INFO Keywords: Cold-formed Steel-concrete structure Structural steel Thin-walled Welded sections ABSTRACT This paper presents the structural upgrade of a public school building, which did not guarantee safety against collapse under gravity loads and which had been designed ignoring seismic actions. The design of the upgrade took full advantage of the properties, capabilities and opportunities afforded by steel, which was used in a variety of forms and functions — namely, cold-formed members, thin-walled sections, welded elements, steel-concrete horizontal and vertical structures. The activity presented here did not use numerical calculation as a means of structural design. The multifarious roles that steel can play make steelwork particularly suited to conservation and upgrade of twentieth century architecture, especially seminal reinforced concrete buildings. 1. Introduction Starting in the late 1990s, the Reinforced Concrete (RC) buildings of the postwar rebuilding and the following construction boom began to reach fifty years of age, the point at which in Italy they typically become eligible for heritage protection (while the first generation RC buildings had already reached that age). Along with the growing appreciation of those structures, and not only in the case of seminal buildings, is the search for a new approach to conservation for the buildings constructed in the twentieth century, as the traditional conservation theories and techniques are devoted to masonry con- structions and, as such, are not suited to RC structures (let alone to steel structures) [1–6]. The materials and construction methods of the latter have challenged traditional conservation theories and techniques, and raised new conservation issues [7–15]. The problem is particularly acute for buildings in seismic areas [13–17], since the common seismic retrofit techniques for RC constructions that were not designed to withstand seismic actions do not retain authenticity. There have been some research attempts to blend structural and conservation issues for twentieth century architecture [1,5,7,15,17–19], but the topic remains ongoing. A viable and suitable solution is offered by steel structures [20–28]. This paper deals with a public school building (Fig. 1), located in Montelabbate, a town close to Pesaro, in Italy (Marche Region), which had been destined for demolition. The building represented a typical RC framed structure of the 1960s. Although not being a ‘Listed Building’, the edifice was of interest and importance, since it was of good quality design and appearance. Moreover, not only was the building attractive in its own right, but also it contributed to the character and appearance of the area where it was (and is) located. In fact, the building, which was the only elementary school of the town, illustrated, and was reminder of, the historical development of that area. For those reasons, the building was worthy of recognition and retention as much as possible. The paper presents the key features of the structural work — design and construction — that provided that building with the capacity of resisting the loads prescribed by the current Italian code. That work saved the school from demolition, maintaining the building's architec- tural integrity. Now the building continues to serve as the public school of the town and conserves the original character and appearance, since the new structures neither gave the building a new look nor hid the original building nor even obscured it. Part of the addition was concealed behind the suspended ceiling or was placed in the attic, while the design made the other part identifiable. The design was the result of mental conceptual models and simple manual analytical calculations, by which the author comprehended and explained how the design would have worked in reality, governed the relationships between existing and new structures, and obtained realistic assessments. Neither numerical modeling nor code compliance checking was performed during the design process. When the entire structure had been completely defined at the end of the design process, the author assessed the design of the structural work he had planned to do and provided a certificate, in the form of a signed report, stating that the entire structure had been designed to comply with the Italian structural code. Assessment was accomplished according to the provi- sions of the Italian code and certified that the designed structure http://dx.doi.org/10.1016/j.jobe.2016.10.003 Received 25 August 2016; Received in revised form 7 October 2016; Accepted 7 October 2016 E-mail address: paofor@iuav.it. Journal of Building Engineering 8 (2016) 107–122 2352-7102/ © 2016 Elsevier Ltd. All rights reserved. Available online 08 October 2016 crossmark