PSI - Issue 44

Ingrid Boem et al. / Procedia Structural Integrity 44 (2023) 2238–2245 I. Boem, B. Patzák, A. Kohoutková / Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction The application of textile-reinforced mortar coating as strengthening technique for existing masonry buildings is widespreading in the refurbishment building market, due its particular effectiveness in increasing the walls resistance against in-plane and out-of-plane seismic actions (Kouris and Triantafillou, 2018; Garcia-Ramonda et al., 2021; De Santis, et al., 2019). Composite Reinforced Mortar (CRM) is an innovative textile-reinforced mortar strengthening technique (Fig. 1a), which consists in the application, on one or both the masonry surfaces, of a mortar coating having a nominal thickness of 30 mm, with embedded composite pre-formed grids made of Glass Fiber-Reinforced Polymer (GFRP) yarns. Moreover, GFRP L-shape connectors are injected into holes in the masonry. In-depth experimental studies for the characterization and evaluation of the effectiveness of this strengthening techniques have been performed in the last 10 years. In particular, tensile and shear-bond tests on CRM coupons (Gattesco and Boem, 2017a) allowed to investigate on the equivalent tensile behavior of the composite material and on the minimum bond length to avoid premature debonding phenomena (of the grid from the mortar, as well as of the mortar from the masonry). Furthermore, tests on masonry samples (Gattesco and Boem, 2015; Gattesco and Boem, 2017b, Boem and Gattesco, 2021) evidenced the effectiveness of CRM against the typical failure mechanisms of masonry elements subjected to in-plane actions (diagonal cracking and in-plane bending failures) and out-of-plane actions (out-of-plane bending failure). Basically, the CRM layer acts in tension, carrying the tensile stresses once cracking occurs and spreading the damage; this reflects in significant improvements in both resistance and displacement capacities, as well as in terms of dissipated energy. Besides experimental testing, numerical models were developed to investigate on materials interactions and resisting mechanism. In particular, in the context of the EU-funded “conFiRMa” project (2020-WF-02-2019 No. 101003410), a multi-level numerical approach for the assessment of the structural performances of CRM strengthened masonry has been developed (Boem, 2020). The former, detailed-level modelling has been calibrated on the basis of experimental tests on individual materials (the masonry, the mortar and the GFRP mesh) and interfaces (yarn-yarn, yarn-mortar, mortar-masonry) and has been validated through comparison with characterization tests on CRM coupons and on CRM strengthened masonry samples (Boem, 2022; Boem et al. 2022a). The subsequent, intermediate level model is based on multi-layer elements, to get a more computationally efficient system and investigate on wider masonry elements and structures (Boem et al., 2022b); this simplified model has been validated through comparison with the experimental and the detailed-level model outcomes concerning single leaf, solid brick masonry samples strengthened with CRM. In this paper, the intermediate, multi-layer modelling approach is applied to the simulation of a new set of experimental tests recently performed on double-wythe rubble stone masonry walls. In particular, the tests concerned masonry piers subjected to in-plane and out-of-plane horizontal cyclic actions (Gattesco et al., 2022), to assess the effectiveness of CRM on full-scale structural elements subjected to reverse loading actions. The application of CRM only at one side of the masonry, in combination with the introduction of artificial diatones, was also investigated.

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Fig. 1. The CRM strengthening technique: (a) application on a masonry pier and (b) schematization of a 20-nodes multi-layer element.