Closed-form solution for NSM strengthening systems applied to brittle substrates

The article presents the results obtained by using an analytical model herein slightly modified to study Near Surface Mounted (NSM) CFRP strengthening applied to brittle supports. To this scope, three sets of lab investigations comprising CFRPs applied to concrete and masonry pillars were considered. The lab investigations comprised testing of different CFRP strips characterized by various geometrical (cross section and bonding length) and mechanical parameters (elastic modulus). The interfacial tau-slip laws adopted in the analytical model were tuned using available experimental data and idealized bilinear laws proposed by the authors in the experimental campaigns. The reliability of the model was assessed by comparing the global force-slip curves obtained experimentally and analytically. Also, the analytical model allowed estimating the axial stress in the FRP strengthening, providing valuable information about the most probable failure mode (i.e., debonding or fiber failure). A global satisfactory agreement was found in all the set of tests studied with the proposed model. The analytical approach was able to accurately estimate the initial stiffness, peak load and post peak behavior.