Fibre-reinforced composite materials have gained an increasing success, mostly for strengthening, retrofitting, and repairing existing structures. However some problems may arise with the use of traditional FRP (Fiber Reinforced Polymer), particularly when the compatibility with the substrate and the reversibility of the intervention are required, as in case of cultural heritage buildings, or specific exposition conditions may compromise the long term effectiveness of the reinforcement, as in presence of high temperature and humidity. Starting from these considerations new composite materials are emerging as a more effective solution in certain fields of application and under specific service conditions; in this context, mortar-based composite systems, consisting of one or more layers of uni- or bi-directional fibre nets embedded in cement/lime-based matrix layers, can be used as reinforcement of both concrete and masonry structures. However, the research work dealing with these emerging materials and their performances when used as a strengthening system for existing structures is still limited. Both experimental and theoretical investigations are needed in order to deliver reliable design methodologies. In this work, a Round Robin Test aimed to the characterization of both bond with the existing substrate and tensile performance of glass fabric (in the form of grids) coupled with inorganic mortar matrices is presented. The investigation was conducted at fifteen laboratories involved in the RILEM Technical Committee 250-CSM (Composites for the Sustainable Strengthening of Masonry). With the aim of studying the bond behaviour between Fabric Reinforced Cementitious Matrix (FRCM) composites and masonry substrate, single and double lap shear tests were carried out on brick-masonry prisms. Results provide useful informations about the mechanical properties, the bond capacity and the failure mechanisms of different commercially available glass FRCM systems. Finally, critical aspects are underlined to address the progress of the research work.

Glass fabric reinforced cementitious matrix: Tensile properties and bond performance on masonry substrate

Experimental and analytical study to evaluate the effectiveness of an in-plane reinforcement for masonry walls using GFRP meshes

Ancient masonry arches and vaults strengthened with TRM, SRG and FRP composites: Experimental evaluation

Experimental and numerical study on the shear behavior of stone masonry walls strengthened with GFRP reinforced mortar coating and steel-cord reinforced repointing

In the paper, the results of an experimental and numerical study on the out-of-plane bending effectiveness of a modern strengthening technique applied to existing masonry walls are presented. The technique consists in the application, on both wall faces, of a mortar coating reinforced with glass fiber-reinforced polymer (GFRP) meshes. Four point bending tests of full scale masonry samples (1000 width, 3000 mm height) were carried out considering three types of masonry (solid brick, 250 mm thick, rubble stone and cobblestones, 400 mm thick). The performances of plain and reinforced specimens were analysed and compared. It emerged that strengthened specimens are able to resist out-of-plane bending moments almost 4–5 times greater than those of plain specimens; moreover they can overcome deflections more than 25 times higher, due to the presence of the GFRP mesh, which contrasts the opening of cracks. The cracking and the ultimate bending moments of reinforced samples can be analytically predicted using relationships quite close to those used in the design of reinforced concrete beams subjected to combined axial and bending actions. The results of nonlinear static analyses performed on a 2D numerical model were also presented, so to comprehend the mechanical behaviour of reinforced masonry walls. Their agreement with the experimental results proved the reliability of the simulations; moreover, the extension of the 2D model to a 3D one, necessary to analyze the behavior of perforated walls, was also made.

Out-of-plane behavior of reinforced masonry walls: Experimental and numerical study

The paper presents the results of a broad experimental investigation conducted through diagonal compression tests on masonry specimens strengthened with a mortar coating applied on both surfaces of the wall and reinforced with a glass fiber reinforced polymer (GFRP) mesh. Four types of masonry, three different types of masonry mortar and five diverse GFRP meshes for the reinforcement were considered. In particular, solid brick masonry 250 and 380 mm thick, two-leaf brick masonry with rubble conglomerate infill and rubble stone masonry were tested. The diagonal compression tests, performed on 60 square masonry specimens with loading-unloading cycles up to the collapse, evidenced a good effectiveness of the strengthening technique in terms of both resistance and ductility. Results also showed the resistance increment in reinforced samples is generally greater for weaker masonry types and, referring to a single masonry type, for specimens built with a weaker mortar. Furthermore, the different GFRP meshes influenced very little the resistance of specimens, but higher reinforcement contents induced a lower decrease of the diagonal load after the cracking.

Diagonal compression tests on masonry walls strengthened with a GFRP mesh reinforced mortar coating

An experimental investigation was carried out under cyclic loads to evidence the performances of particle board shear walls when subjected to earthquake excitation. Shear walls of different dimensions and different connection arrangements were studied and some of them include also one opening for windows. The experimental tests evidenced significant differences between the code model and the actual results both in terms of shear resistance and stiffness, with particular concern for shear walls made with more panels or for perforated walls.

Experimental investigation on the seismic behavior of timber shear walls with particle boards

This paper presents the results of a laboratory investigation carried out on reinforced mortar plates. Reinforced mortar plates are often applied for shear reinforcement of wall panels. Different reinforcement materials have been embedded into the mortar plates: GFRP (Glass Fiber Reinforced Polymers) grids, fiberglass fabrics and welded steel-wire meshes. This is the first stage in the development of a new type of GFRP-reinforced mortar jacketing, that will provide a solution to enhance the lateral capacity of historic buildings. Such reinforced plates can also be used in applications on new masonry constructions where buildings with damaged or cracked wall panels need to be repaired or retrofitted. The mortar plates were built from commercially available GFRP grids and fabrics that were embedded into the mortar to form a reinforced-mortar square structure of 1 m with a thickness of 30 mm. The plates were tested in the laboratory, under quasi-static patch loads that exceeded the expected seismic loads. The goal of the testing program was to assess the design and construction techniques used, with a view to designing the reinforcement of a historic building. The laboratory tests demonstrated that the GFRP-reinforced plates had sufficient stiffness and strength to function effectively. By comparing the results with the more traditional steel-wire mesh reinforcement, it was also possible to perform a comparative analysis.

Reinforced Jacketing of Wall Panels: A Comparative Experimental Investigation

The results of a first experimental research program on masonry vaults strengthened by means of GFRP meshes embedded in a thin layer of lime mortar, are herein presented. The tests were designed to reproduce the pattern of a transversal horizontal load proportional to the vault self-weight. The typical simplified loading patterns generally used for the experimental tests concern concentrated vertical loads at the crown section or at 1/4 of the span, but some numerical investigations evidenced that these configurations are not able to reproduce the actual behavior and the effectiveness of the reinforcement. So a specific rig was designed to apply the horizontal load pattern.Solid brick masonry barrel vaults were considered (thickness 120 mm, arch span 4000 mm, arch rise/radius = 0.75). Three quasi-static cyclic tests were performed: the first concerned an unreinforced vault, the second a vault reinforced at the extrados through the application of a mortar coating reinforced with a GFRP mesh and the third reinforced at the intrados surface with the same technique. The experimental results demonstrated the technique effectiveness and the important increment of ductility of the vaults.

A. Dudine

Papers

Diagonal compression tests on masonry walls strengthened with a GFRP mesh reinforced mortar coating

Experimental investigation on the seismic behavior of timber shear walls with particle boards

Reinforced Jacketing of Wall Panels: A Comparative Experimental Investigation

Experimental behavior of masonry vaults strengthened with thin extradoxal or intradoxal layer of fiber reinforced lime mortar

Il rinforzo di murature esistenti con intonaco e rete in GFRP