PSI - Issue 44

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Corrado Chisari et al./ Structural Integrity Procedia 00 (2022) 000 – 000

Corrado Chisari et al. / Procedia Structural Integrity 44 (2023) 1108–1115

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1. Introduction Italy has one of the largest shares of UNESCO world heritage, which needs to be preserved because of the high seismicity of the national territory. Recent studies on seismic vulnerability have clearly shown that masonry arches and vaults, largely present in churches, monuments, bridges, are among the most vulnerable structural elements (De Matteis & Zizi, 2019). In this context, the main traditional retrofitting techniques used in practice are tie rods or buttresses counteracting the thrust, which produce a significant change in the aesthetics and structural behaviour of the original structure. Other methods as Fibre Reinforced Polymers in form of sheets or plates have proved very effective in terms of strength increment (Borri, et al., 2011) but do not satisfy compatibility and reversibility prescriptions for heritage structures. In this sense, the use of lime-based mortar as re-pointing or surface treatment would represent the optimal material, but its low tensile strength and high brittleness make it unsuitable as a retrofitting technique. The introduction of fibres in the mortar paste has been proposed very recently for retrofitting of masonry walls (Bustos-García, et al., 2019) leading to very promising results. The application to arches and vaults, whose mechanical behaviour is markedly different from walls’, was explored with reference to steel fibres (Simoncello, et al., 2019) showing the advantages in terms of vertical bearing capacity enhancement, but also the possible lack of efficiency in case of shear failure of the arch or detachment of the reinforcement, which prevents the attainment of full strength of the system. Numerical investigations confirmed the potential of the technique for seismic retrofitting of buttressed arches when the collapse of the system is governed by the arch (Chisari, et al., 2021). This paper will explore the effectiveness of Fibre Reinforced Lime-Based Mortar (FRLBM) applied at intrados in increasing the horizontal capacity of circular arches. To this aim, a specific experimental setup was designed, in which a set of half-scaled arches was subjected to both constant vertical loading simulating the effect of backfill and variable horizontal load on a point approximately located at the arch barycentre height. Nonlinear numerical finite element models were then developed to simulate the experimental response and investigate the effect of various material parameters on the overall response. The materials used for the arch construction were selected to resemble historical materials used in Campania region (Southern Italy). The arches were made of yellow tuff blocks and pozzolanic mortar, whose mechanical characteristics were estimated by means of appropriate material tests. In particular, the following tests were performed: - Flexural tests on mortar for the determination of tensile strength and ductility, according to EN 1015-11 (Fig. 1a); - Compressive tests on mortar, according to EN 1015-11 (Fig. 1b); - Compressive tests on tuff stone cubes according to EN 772-1 (Fig. 1c), and tuff-mortar assemblies according to ASTM-C1314-03b (Fig. 1d); - Flexural tests on tuff stones according to EN 12372 (Fig. 1e); - Triplet tests according to EN 1052-3 with different pre-compressions, for the determination of cohesion and friction angle of stone-mortar assembly (Fig. 1f). The tests for mortar were performed on three types of mortar: (i) pozzolanic (used as connection between blocks), and (ii) ordinary reinforcing M15 mortar and (iii) FRLBM as reinforcement. The results are reported in Table 1. 2. The experimental program 2.1. Material tests