Analytical Bond-Slip Model for Fiber-Reinforced Cementitious Matrix-Concrete Joints Based on Strain Measurements

An accurate bond-slip model is of fundamental importance to analyze the response of fiber-reinforced cementitious matrix (FRCM) composite-strengthened structures. This study proposes a method to determine the bond-slip model of FRCM-concrete joints based on longitudinal fiber strains. First, discrete strain profiles measured with strain gauges were fitted by a continuous function $\epsilon (y)$, where $y$ is the coordinate along the bonded length. Then the slip $s(y)$ and shear stress $\tau$ ($y$) along the composite bonded length were obtained by integration and derivation of $\epsilon (y)$, respectively. The debonding load and peak load from single-lap direct shear specimens were predicted by the fitted function $\epsilon (y)$ and showed good agreement with test results. From the plot of the $\tau (s)$ relationship obtained from $\epsilon (y)$, an alternative, closed-form, continuous bond-slip relationship was obtained based on the maximum shear stress ${\tau }_m$ and the corresponding slip $s_m$. The fracture energy was compared for both relationships and was in reasonable agreement with values reported in previous studies.