Church activities continue during restoration work

Church activities continue during restoration work

Inside the Basilica of St Peter in Rome, the mosaics of the St Pius dome, which date from the 16th century, are in the process of being restored. The first conservation measures were carried out in the 17th century and the most recent in 1840.

“From the working platform it was possible to gain access right up to the dome lantern in safety.”

The work, which could possibly last for more than one year, has presented those responsible for the day-to-day running of the church with a significant problem. It is essential that access to the church is provided at all times for visitors and worshippers and this was a priority throughout the duration of the restoration work. No part of this important centre of cultural interest was to be closed, even for safety reasons.

Scaffold construction

The nature of the historically important building and the requirement to keep any disturbance to normal church activities to a minimum necessitated reduced assembly and dismantling times for the scaffold. The planning of the scaffold construction proved to be particularly extensive and complex.

Using the PERI UP scaffold system a solution was provided which made it possible to erect a ‘floating’ working platform in barely one week. This solution resulted in ideal conditions for the team of experts to carry out the planned restoration. The platform also guaranteed both the safety of workers carrying out the work and visitors below the platform.

Support scaffold was assembled to facilitate the erection of the working platform at a height of nearly 26m. This also served as an intermediate storage facility and access point up to the time when the platform was mounted in its final position. The high node rigidity of the PERI UP Rosett system allowed the assembly, and later the dismantling, of the temporary shoring tower from the floor to the required height without any anchoring, support or other securing equipment to the church building itself.

This was followed by the assembly of the 124m^sup 2^ working platform. The construction of the platform proved extremely difficult at first due to an insufficient number of possible anchor positions. Before the actual assembly work began, PERI engineers developed four different, computer-aided spatial models. They designed an efficient solution using PERl LGS girders that were suspended over a length of 17.5m. Node braces were then mounted to the girders in the form of a balanced cantilever. The skylights of the four large windows of the elliptically-shaped dome could be used as points of support. The combination of girders and PERI UP Rosett components formed the basic construction of the platform. This was rounded off with radially-positioned PERI VT timber I-beams with a plywood and linoleum covering.

After completion of the ‘floating’ working platform, the shoring tower, together with the access ladders (which were needed only to construct the platform) was dismantled. For the restoration team, accessing the platform took place via the outside of the dome and through the large, opened windows at the height of the vault transom. From the working platform it was possible to gain access right up to the dome lantern in safety.

Access decks with an integrated ladder system allowed climbing up and down to be made as easy as possible. The working platform was designed for a maximum load bearing capacity of 200kg/m^sup 3^.

Load distribution

Early calculations resulted in all the shear forces affecting the thicker vaults to be transferred to the support points for the auxiliary construction and from there to the main columns of the basilica. The weight of the structure was determined while considering the load capacity of the basilica’s structure and load distribution.

When work is carried out on buildings of great architectural importance there are frequent technical difficulties. Even moving the required materials and equipment, which would appear to be of minor importance in other construction site projects, becomes significant. Design planning for the scaffold construction work was therefore carried out with special care and attention.

Concluding remarks

The use of the working platform ensured that regular church activities remained totally unaffected for the entire duration of the dome renovation work.

Copyright The Concrete Society Mar 2005

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