In today’s construction industry, structural repairs and reinforcement using fibre reinforced polymers (FRPs) are being preferred against classical methods of reinforcement using steel and reinforced concrete. FRP fabrics, impregnated with resins, are applied directly onto existing masonry and concrete structures allowing contractors to strengthen or repair their structures in a quick and effective way.

Italian company C-Six srl was established to address the increasing demand of the market in the use of FRP for structural repairs and strengthening. The products are focused around C-Tex, which is an innovative carbon fibre fabric, developed thanks to specialist research and rigorous testing carried out both in expert laboratories and on site.

C-Six srl provides technical expertise in designing the structural system using its product as well as contracting services to ensure the correct installation of their products, by highly qualified workers with many years of experience.

The superior face of the vault was cleaned in order to be able to bond the carbon fibre stripes.The superior face of the vault was cleaned in order to be able to bond the carbon fibre stripes.

The application of this technology took place last year while strengthening the vault of St Francis church in Valletta. C-Six srl carried out the works, with both Ing. Michelangelo Micheloni and Perit Duncan Polidano, who led the design works and project management.

St Francis church, which is located in the centre of the capital city, was built between 1598 and 1607. During World War II a bomb hit the church directly. Besides leaving considerable damage within that area, the blast also caused severe damages in the rear part of the church, particularly the vaulted end behind the altar and lantern above (as indicated in the pictures).

The repair and strengthening of the choir vault was carried out by stitching carbon FRP stripes on the top and bottom faces of the vault. There was no need to dismantle the lantern. It was important to determine the exact geometry of the vault and the characteristics of the materials. In addition to the geometrical surveys, compression tests on samples of the existing stone were carried out to determine the mechanical properties.

With this information, the structural calculations and design was carried out to determine the exact layout and the quantity of FRP strips. The design also provided the level of safety of the structure for stability, static vertical loads and horizontal seismic loads. Once the execution of works was complete, a full set of in-situ tests were carried out to confirm the design assumptions.

Finally, the roof finishes on top of the vault and the frescos on the lower face of the vault were re-applied. Today, the structural intervention is completely invisible, making this form of intervention the quickest and most cost-effective in this case, with no intrusion at all to the existing appearance of the structure.

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