Experimental assessment of partial factors for externally bonded inorganic matrix composite reinforcement systems

Inorganic matrix composite (IMC) systems represent a sustainable solution for masonry strengthening, thanks to their compatibility with substrates, low costs and good performances in extreme conditions. Among them, FRM (Fabric Reinforced Matrix) systems employ dry fabric embedded in lime or cement-based mortars. The design of this strengthening technique relies upon the definition of the design strength, which is obtained from the characteristic values through appropriate partial factors, which are commonly indicated in building codes or design guidelines. Following the principle of ‘design-by-testing’ pursued by EN 1990, successfully employed by the authors for the calibration of partial factors for the strengthening technology using organic matrixes, the paper presents the results of a statistical analysis based on a large experimental activity for the qualification of several FRM systems provided by different manufacturers. Results of tensile tests under standard ambient conditions were used to calibrate the partial safety factors related to the materials. The paper will discuss the obtained results in comparison to the factors currently prescribed by design provisions, in particular with the aim of giving an overview of the behaviour of various types of fibres and, therefore, focusing on some aspects which may be the subject of future revisions of design guidelines.