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Composite materials made with textile fibers both with polymeric and cementitious matrices are often adopted for the retrofitting of masonry arches and vaults. A specific project that analyzes the performance of ancient masonry arches and vaults strengthened with composite systems has been recently concluded at Politecnico of Milan. The project involves the experimental evaluation and the development of numerical and analytical simulations. In this paper the experimental campaign is described, whereas the numerical validation is provided in an accompanying paper [1]. The tests were performed in-situ on ancient masonry arches and vault elements. In particular, three barrel vaults and two arches either unreinforced or reinforced with Steel Reinforced Grout (SRG), Textile Reinforced Mortar (TRM) and Fiber Reinforced Polymer (FRP) were tested. The arches had a span equal to 3.30 m, a rise equal to 0.83 m and were built with common Italian bricks regularly spacing out two bricks laid edge on (thickness of the arch 12 cm) with two bricks (one over the other) disposed in single leaf. Barrel vaults had the same geometry of the arches but were made with a single leaf. In all cases, an eccentric vertical load was applied at ¼ of the span and was increased up to failure. The experimental results on unreinforced structures are compared with those obtained on the strengthening ones in terms of failure mode, maximum load, stiffness and ductility.

The paper presents an experimental study concerning the bond behaviour of Carbon Fiber Reinforced Polymers (CFRP) sheet reinforcements applied to curved masonry surfaces. Such strengthening technique is more and more used in structural rehabilitation and retrofitting of existing buildings. Its effectiveness has been demonstrated by several studies published in the literature, mostly devoted to flat bonded surfaces. Seeing that CFRP are extensively applied on arches and vaults but only few research activities concern curved bonded surfaces, the experimental study described in this paper is aimed to contribute to fill this gap. The experimental program was carried out on portions of masonry arches, reinforced by CFRP sheets bonded at extrados or intrados, tested by a single lap shear test. The experimental results allowed to analyse the effectiveness of such reinforcements, loaded by actions tangent to an end of the reinforcement itself, with respect to its position (intrados or extrados) and to the curvature of the bonding surface. As expected, the results highlight that the bond behaviour strongly depend on the position of the reinforcement. In particular, the capacity of reinforcements bonded at the extrados increases with the curvature, while decreases with the curvature for those bonded at intrados.

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