MULTI-LEVEL MOBILE SCAFFOLDING IN THE GALLERIA
The history of the Galleria is also the story of a great construction project. Little time and money, and great ambitions are dating back to 1865. It is very interesting to browse the numerous photos from the archive. One picture in particular stands out among the others, which is of the great multi-level mobile scaffolding in the center of the Octagon, which had been set up to construct the Dome. This was the first mobile scaffolding in the Galleria to be mounted on a system of wheels running on wooden tracks.
The Galleria is an engineering feat that pushed technology of its time to its limits and was therefore very complex. The glass sheets that are used are fragile and the decorations delicate. Maintenance, though not continuously necessary as is the case for the nearby Duomo, is yet very frequent. Debates around it therefore are not unusual. The monument is often subjected to ordinary and extraordinary maintenance work. Numerous of archival photographs show past restoration interventions. On a winter evening in the 1980s, the Galleria’s façade was completely hidden behind scaffolds.
THE ARCH SCAFFOLDING
A deep understanding of past interventions, the willpower to preserve free access to the shopping areas, the need to ensure security and to optimize construction time limitations were all reasons which have encouraged reflection in search of a "creative" solution. The aim was ambitious: to carry out restoration works without any scaffolding. The classic way of doing it, using vertical lift platforms, soon proved unfeasible, given the considerable vertical area to be covered (over 40 meters) and the delicacy of the floor. In the face of this apparent impossibility, the desire to find a solution became stronger, encouraged by the belief that the Galleria could not be "wrapped up" for a year. The idea originated from the creativity of a construction company that turned what appeared to be just a dream into a 'machine': "we cannot dismantle tents, obstruct access ways to shops, assemble scaffolding for too long, in short, we must restore the Galleria as if we were flying". The “flying scaffolding”, or mobile scaffolding, represents the translation of this approach and these goals into engineering terms. A work plain that has moved the bulk of scaffolding above the heads of pedestrians and shops windows, by leaning on the ground floor on eight punctual elements, reducing obstruction to a minimum.
The scaffolding is only 15 meters high and at the end of each working phase it moves to the next one. As the scaffolding arch moves forward, it leaves behind the parts of the facade that have been restored. The idea was made into an artefact after a thorough survey of the Galleria’s geometry and the analysis of the ground floor subfloor load. The Galleria, which was rapidly built around 1860, is almost a perfect work of art, with just a 3-mm tolerance from the top to the bottom of its longer arm. Therefore its possible to cover it all with a large machine, a sort of "spacecraft" which is home to the restorers, protects pedestrians and safeguards shop owners.
USER SAFETY NEEDS
The arch scaffolding provides a complete self-propelled passage through the Galleria to the entrance of the stores, preserves the perspective view of the Galleria as a whole and does not obstruct the visibility of the shop windows. The movements have been planned to take place at night so as not to cause any inconvenience to visitors.
COMPLIANCE WITH COMMERCIAL ACTIVITIES
The mobile scaffolding does not interfere with activity of the surrounding restaurants and cafés, thus allowing the conservation of the outdoor areas.
The arch scaffolding has made it possible to extend the time allocated to the restoration by compressing the logistic operations. The structure on the side of Piazza della Scala was assembled in a week and thanks to a system of wheels on rails and jacks, it has moved along the main nave at a pace of three bays at a time. It will reach Piazza del Duomo in December. In less than a week, it will be dismantled and reassembled on Via Silvio Pellico, and in four months will cover the shortest side of the Galleria. How spectacular the two movements through the Octagon are!
PRESERVATION OF THE HISTORIC PAVEMENT
The arch scaffolding project has been developed taking into account the delicacy of the floor. The tracks run along the toughest portion of the floor, avoiding the glass rose windows.
REDUCTION OF CONSTRUCTION SITE ACTIVITIES
The arch scaffolding was assembled during the night, temporarily occupying the area. Firstly, a metalwork structure on wheels was installed, and then the top scaffolds were mounted to cover the two sides of the façade under restoration. Finally, custom-made tarpaulins were installed to close off the scaffolding on all sides.
The mobile scaffolding project, designed specifically for the restoration of Galleria Vittorio Emanuele II, was inspired by specific examples from architectural history. The designers recalled one of the greatest engineering and architectural feats in history, the construction of the dome of the Santa Maria del Fiore Cathedral in Florence, for which Brunelleschi was at once architect, engineer and foreman. The first sketches of the arch scaffolding recall the struts used to support the weight of the scaffolding of the famous sketch by Giovan Battista Nelli and stored at the Uffizi Museum.
The requirement of a scaffolding without ground support recalls the images of technically daring projects, such as those designed by Nicola Zabaglia, master builder of the Fabbrica di San Pietro, an uneducated foreman that was later appointed architect of St. Peter's, thanks to the technical boldness and financial care of his machines. Finally, the solution to complex problems is always rooted in the knowledge of experience in this sector, combined with the addition of related competences. Historically, the shipbuilding sector has the most experience solving complex logistics challenges associated with the handling of heavy loads. The designers have looked at the mobile scaffolds used in shipyards and have used them as inspiration. Here in the Galleria, the competences of ancient construction companies combined with “industrial” principles have been applied to give birth to an important construction experiment never conducted before.
THE ARCH SCAFFOLDING OF IMPRESA PERCASSI s.r.l. FROM SCAFFOLDING FOR RESTORATION TO COMMUNICATION TOOL
of wooden structure
total weight of the mobile scaffolding
washers used for the construction
cage nuts used for assembly
screws used for the fastenin
and 15 meters: advancement period
hours for assembly and displacement
of design and research