Design of FRCM Strengthened Masonry Walls Subjected to Out-of-Plane Loading According to CNR-DT 215: Discussion of the α Coefficient

Fiber-reinforced cementitious matrix (FRCM) composites are largely employed in Italy to improve the mechanical behavior of masonry members. Many different matrices and fiber textiles are available on the market, which entails for a large number of available composites, each with peculiar mechanical and physical properties. Among the possible applications, FRCM are often externally bonded to masonry walls to increase the wall shear capacity or to prevent possible wall out-of-plane failure. Up to date, only two guidelines are available for the design of FRCM strengthened masonry members, namely the American ACI 549.6R and the Italian CNR-DT 215. In the Italian guideline, the bending strength of an FRCM strengthened masonry wall is associated with the performance of the composite - which is investigated by FRCM coupon tensile tests and FRCM-masonry joint bond tests - through a cross-sectional equilibrium that assumes perfect bond among each material.In this paper, a database comprising 90 experimental tests on FRCM-strengthened masonry walls subjected to out-of-plane loading is collated from the available literature. The experimental results are used to compute the composite effective strain, which is then compared with the corresponding composite maximum strain obtained by characterization tests according to the CNR-DT 215 procedure. The comparison sheds light on the role of coefficients employed in the analytical procedure and helps understanding the influence of the FRCM on the wall bending capacity.