Key Engineering Materials Vol. 916

Abstract: Historic masonry buildings are complex structures whose behavior is strongly affected by the quality of materials, by traditional constructive techniques and by alterations occurred over centuries. Therefore, it is important to deepen the knowledge of existing buildings in order to identify potential vulnerabilities and to define suitable reinforcing interventions. In order to properly deal with cultural heritage criteria these interventions must satisfy not only the structural requirements but also the conservative issues. In this regard, each retrofitting intervention should be planned according to the specific case, acknowledging all the peculiar features that should lead to the definition of a proper reinforcing solution. Consequently, it is not possible to uncritically apply a generic reinforcing system given by manuals in compliance with standard typologies of traditional architectural elements.In this paper several case studies located in Parma (Italy) will be presented in order to highlight the need of a critical approach based on a deep knowledge of existing buildings. In particular, the given examples are focused on strengthening interventions carried out on vaulted structures. Sometimes composites proved to be one of the most effective reinforcing solutions for these masonry elements, allowing to improve the structural strength without increasing its stiffness. The strengthening intervention, designed according to both structural and conservative issues, definitely proved that a critical awareness is fundamental for a positive contribution of non-traditional techniques – such as composites – applied to traditional masonry structures.

Abstract: Seismic events recently occurred in Europe highlighted the vulnerability of unreinforced masonry structures, representing the majority of the built heritage, to earthquake-induced loads. In particular, the in-plane capacity of shear walls under seismic loadings appeared sensibly modest, both in terms of strength and ultimate displacement, and their failure mode sudden and brittle. Textile Reinforced Mortar (TRM) composites proved to be a proper strengthening solution for the seismic upgrade of such walls. With the aim of gaining a deeper knowledge on the behavior of historical walls retrofitted with TRM and subjected to compression-and-shear, this paper summarizes the results of an experimental campaign characterized by quasi-static cyclic shear-compression tests. The specimens under study reproduced the rubble stone masonry typical of vernacular structures of the UNESCO historical district of Lyon (France). Specifically, the work concerns a full scale masonry wall tested under loading until the development of diagonal cracks and than repaired by a composite constituted by a basalt textile embedded in a lime mortar matrix applied onto the external surfaces as a plaster. The use of a lime mortar plaster to reinforce the structural element permits the development of a solution compatible with the historical substrate. Experimental outcomes revealed how Basalt TRMs succeeded in improving the response of damaged vernacular wall, both in terms of strength and displacement capacity.

Abstract: Although, over the last decades, different types of additions have been used in mortars for conservation of heritage buildings, their use in lime-based grouts for stone masonry consolidation is limited. The purpose of this study is to contribute to the increase of knowledge regarding the performance of injection grouts prepared with glass microspheres and polypropylene (PP) fibers. The effects of glass microspheres and PP fibers on the properties of natural hydraulic lime-based grouts were analysed by rheological measurements, mechanical strength tests, water absorption and drying test. The content of glass microspheres (5-20%) and PP fiber (0.1-0.5%) was added by the weight of binder and to reduce the water demand, a polycarboxylate superplasticizer was used. From the assessment of the results, it was asserted that the fresh state behaviour was slightly affected by these additions, as in general the rheological properties worsened compared to the reference grout composition. On the other hand, the PP fibers influenced the hardened grouts’ properties in a positive way, while their mechanical and physical properties were slightly improved or maintained which is a crucial feature for the success of consolidation intervention.

Abstract: There is an emerging need to upgrade historic masonry buildings and infrastructures which are most vulnerable to earthquakes. An objective of a long-term research program at Perugia University, Italy was developing design criteria for masonry reinforcement using a new class of materials, using Composite Reinforced Mortars (CRM). These are typically made of fiberglass meshes embedded into a cementitious or lime mortar, which offers higher sustainability features, in terms of vapour permeability and compatibility with masonry, lower costs, and better performance at high temperatures, compared to more traditional steel rebar jacketing or epoxy-bonded composites. These design criteria have been based on a comprehensive experimental and numerical research plan that included a study of the influence of reinforcing material, coating and wall thickness, and associated masonry strength and elastic properties, and the interaction of different stress states on bond behavior at interface masonry-to-coating. A design equation suitable for ultimate load design has been developed. Finally, analytical models regarding the lateral capacity of shear walls are briefly discussed.