During the workshop, a special focus will be given to innovative techniques to be used to avoid the delamination of FRPs from the substrate. Kimia developed a full range of anchoring solutions, among which a special mechanical locking system, Kimitech FRP LOCK, is used to better exploit the resistances theoretically ensured by the composites preventing the delamination of the fibers from the substrate. That feature is particularly useful when reinforcements are applied:
- on poor quality substrates, where a cohesive failure on the cortical layer of the strengthened element is usually attained for stress-stains values lower than the ones the fibers could withstand;
- for the reinforcement of elements undergoing dynamic stress conditions: without end connections and by following the movements of the structure, the composite is likely to be disconnected from the support when subjected to compression, being, therefore, unable to exert its resistance in the subsequent phase in which would have worked in traction.
A special version of Kimitech FRP-LOCK®, called Kimitech FRP-LOCK PR (figure 1), was used to anchor Michelangelo’s Pietà Rondanini statue to a new anti-seismic basement during its relocation inside Palazzo Sforzesco in Milan.
The seismic assessment project of the “Pietà Rondanini” coordinated for the structural aspects linked to the repositioning of the statue by Eng. Devis Sonda (Miyamoto International), won the “Global Best Project 2016” prize. The award is also a recognition of the work done by Kimia, which developed the anchoring system of the sculpture to the anti-seismic basement.
The famous Michelangelo’s sculpture, dating back to the XVI century, for the opening of EXPO 2015 was located in a new location of Palazzo Sforzesco in Milan (figure 2).
In fact, after 60 years spent in the Hall of the Scarlioni, it has been housed in one of the lovely rooms recently recovered from the ancient Spanish Hospital. For the occasion, the statue has been placed on an advanced anti-seismic basement able to make it immune from both seismic actions and frequent vibrations generated by the visitors and by the passage of the underground trains nearby (figure 3).
Because of the priceless artistic value of the statue, the exceptional work of relocation of the sculpture represented an opportunity for more competent companies to show their skills and technologies. Kimia was called to cope with the locking system to be applied under the basement of the sculpture.
The idea of realizing a locking system with composites is born from the thirty-years-experience of Kimia in the field of structural reinforcements with these materials.
Kimitech FRP-LOCK® PR is realized through a lamination process of the carbon fiber fabrics around a metallic core. It looks like a disk made of composite material in which the base forms the bonding surface, the core is used to fasten a metal cylinder incorporated and blocked into the basement.
The steps prior to the placement of the reinforcement, have been in-depth studied to develop and test - in the laboratories of Politecnico in Milan - the best solution taking into account the necessity to make the intervention both highly strong and reversible (figure 4 ).
1. The anti-seismic and anti-vibrating platform realized by a team of companies, including Eng. Devis Sonda (Miyamoto International), the THK multinational mechanics and the Italians Goppion and Reglass, has been positioned inside the room of the Spanish Hospital. The surface was prepared by a casting of the pourable fiber-reinforced cement mortar Betonfix CR, reinforced with welded steel mesh (figures 5-6).
2. The Statue, properly protected and secured, was brought into the Spanish hospital room. In order to proceed with the bonding of the Kimitech FRP LOCK® PR on the lower surface (figures 7), the statue was raised and maintained in safety for all the necessary processing time. Finally, once screwed the metal cylinder to Kimitech FRP-LOCK PR (figures 8-9), the final positioning has been done by inserting the cylinder into the basement (figure 10).
[by Diego Aisa, Chiara Frate, Federico Picuti]