Influence of spike anchors in the bond behaviour of FRCM systems applied on concave masonry substrates

One of the methods that can be used for strengthening masonry arch structures is through the use of composite systems bonded to the external surfaces, preferably to the intrados, such as textile reinforced mortar systems (FRCM, TRM, SRG etc). The application of such systems to the intrados allows the ultimate load to be increased while keeping the structure in service. The load increment depends on the performance of the bond between the matrix and the masonry substrate and between the matrix and the fabric, and also the radial detachment stresses (normal for the strengthening system) that are generated when applying this technology to concave surfaces must also be taken into account, as they have a negative effect on the load transfer mechanism. Spike anchors are generally used to reduce the negative effect of curvature in order to postpone the debonding process of the strengthening system. This paper presents the results obtained from a direct shear test campaign on curved masonry specimens strengthened with a fiber-reinforced cement-based matrix (FRCM) with pozzolanic reaction and a carbon fiber fabric. In particular, the effects of spike anchors on the load transfer mechanism between FRCM and the masonry substrate are shown. The use of such spike anchors produced, on average, a higher maximum ultimate force than specimens without spike anchors.