The paper presents the experience of a working group within the RILEM Technical Committee 223-MSC ‘Masonry Strengthening with Composite materials’, aimed at developing a standardized, reliable procedure for characterizing the bonding mechanism of masonry elements strengthened with composite materials under shear actions. Twelve laboratories from European universities and research centers were involved. Two different set-ups were compared, for single-lap and double-lap shear tests (the latter in two versions). Four kinds of fiber fabrics, i.e., glass, carbon, basalt and steel, were applied with epoxy resins (wet lay-up system) to clay brick units, for a total of 280 monotonic tests. The results provided information regarding the response of externally bonded-to-brick composites in terms of observed failure mechanisms, load capacity, effective transfer length, and bond shear stress–slip behavior. The test results of the 12 laboratories constitute a set of statistically representative data which may conveniently be used for setting appropriate design provisions and guidelines

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Modern techniques and innovative materials are often quite rapidly proposed and allowed in current practice, even for restoration of historical constructions, in which essential preservation criteria must be taken into account. The considerable variability and complexity of masonry structures and types means that choosing the most appropriate structural models and interventions is particularly difficult, since they must be based on suitable knowledge of both existing and new materials, and on their interactions in environmental and loading conditions. This paper discusses the potentials and limitations of externally bonded composite materials in masonry structures and components, in the light of knowledge acquired from research in the field, together with the requirements and recommendations of codes and restoration documents. The analysis of some case studies is presented, to highlight the advantages and constraints in the use of composites for strengthening historical buildings

The results of experimental research on brick masonry vaults strengthened at their extrados or at their intrados by fiber-reinforced polymer (FRP) strips is presented here. The presence of the fibers prevents the typical brittle collapse that occurs in a plain arch because of the formation of four hinges; therefore, depending on the position and amount of the reinforcement in the strengthened vaults, three mechanisms are possible: (1) masonry crushing, (2) detachment of the fibers; and (3) sliding along a mortar joint due to the shear stresses. Some first theoretical approaches describing some of these mechanisms are discussed, and the formulation of further models based on the local interaction among the constituent materials is proposed. Six masonry vaults strengthened by glass FRPs or carbon FRPs have been tested. The results have pointed out the enhancement in strength and ductility of the strengthened vaults and the influence in the ultimate strength of the width of the strips and of the bond between the laminate and the masonry

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manufacturing, experimental setup, test execution, and determination of test results are provided.

The paper presents a Round Robin Test (RRT) devoted to the characterization of the shear bond performance of fibre-reinforced strengthening systems bonded with epoxy resin to brick masonry.\ud The research was carried out by six laboratories involved in the RILEM TC 250-CSM (Composites for the Sustainable strengthening of Masonry) as a continuation and an extension of a previous RRT1\ud performed within the RILEM TC 223-MSC (Masonry Strengthening with Composites). In this second investigation (RRT2), the same FRP (basalt, carbon and glass textiles) and SRP (comprising steel\ud textiles) composites were tested, but shear bond tests were carried out on both brick units and masonry prisms. The role of the bed joints of mortar was investigated in terms of shear bond strength, load–\ud displacement response curve, axial strains profile along the bonded area and effective transfer length, for each of the four considered strengthening systems. Single lap and double lap testing setups\ud were used and the comparison of experimental outcomes provided a validation of both results and test methods. Finally, test outcomes led to the determination of the mean and the characteristic\ud values of the experimental-based calibration coefficient provided by design codes for the evaluation of the composite-to-substrate bond strength