IL CONSOLIDAMENTO DELLA CRIPTA DEL SACROMONTE DI VARESE
Gaetano Arricobene1, Lorenzo Jurina2
1 Architetto libero professionista, studio@arricobene.it
2 Politecnico di Milano- dip. ABC, lorenzo.jurina@polimi.it
ABSTRACT
The crypt of the Sanctuary of Santa Maria is one of the oldest places of devotion of Sacromonte of Varese, unfortunately affected by structural problems at the end of the fifteenth century, due to the construction of an heavy baroque altar, supported by four slender stone columns placed in the same crypt. The columns were encircled with masonry bricks, unfortunately removed at the end of the nineteenth century, so giving rise to further static problems. As a consequence, the crypt remained inaccessible to everybody since that event.
Due to the pastoral visit of Cardinal Schuster in 1931, a quite invasive structural strengthening was placed in the crypt, that is the construction of six brick pillars, supporting two long steel beams and the above vaults.
Despite the structural efficiency of the solution, the new elements altered the integrity of the crypt, with strong consequences on its historical and artistic value.
From 2000 and 2013 a certain number of consolidation intervention were designed, aimed to remove the masonry pillars and the steel beams, but able to offer an adequate support to the strong applied loads. The last proposal consisted in a lightweight system, located parallel to the stone columns, reproducing , in some way, the shape of the arches. We proposed the application of curved stainless steel profiles, called "structural gazebo", that provided an active contribution to the overall safety, using large diameter screws, placed at the base of the gazebo legs.
The design decisions here adopted permit the preservation of the original structural scheme: the new "gazebo" in fact supports the existing structures, but it does not completely relieve the columns from the applied load. Vaults and columns in fact will continue to play a static function, even if in a reduced manner.
During all the realization phases, a monitoring system controlled the response of the structures, both the new and the existing ones. Some strain gauges applied to the steel structures and to the stone columns allowed to check the transference of the load, during the dangerous phase of the elimination of the old supporting system.The realization of a three-dimensional model in scale 1:10 was very useful and allowed the designers, the client and the supervisors to evaluate the impact that the new intervention would produce in the precious crypt.
Parole chiave/Key-words:
Crypt, Masonry Vaults, Structural Consolidation, Monitoring