Experimental assessment of bond behaviour of FRP on brick masonry

Existing masonry structures represent a significant amount of the architectural heritage. Many of these buildings are vulnerable to earthquakes. Consequently, they need structural improvements in order to meet the seismic requirements of recent building guidelines. In the last decade, there has been a growing interest in the application of Externally Bonded Fibre Reinforced Polymers (EB-FRP) as strengthening and repair materials, due to their high-performance mechanical characteristics, feasibility of application in civil structures, resistance to chemical attacks and other potentials. Brick masonry components are the most suitable substrate susceptible to improvements, due to their more regular surface in comparison with stonework or rubble masonry. The bond behaviour of FRP applied on a masonry substrate is a critical issue for the effectiveness of the technique. In this paper, the results of an experimental campaign on the local behaviour of EB-FRP applied on clay bricks are presented. Experimental failure load results were compared with predictive bond-strength models proposed in literature for concrete substrate. On the basis of measured strengths and local deformations, interface fracture energies were calibrated and an analytical function was proposed as bond stress-slip law. Finally, a bilinear law was calibrated for practical design applications.