Prediction of Load-Slip Behavior of FRP Retrofitted Masonry

The out-of-plane bending resistance of a fiber-reinforced polymer (FRP)-strengthened masonry wall is generally governed by debonding failure mechanisms. The behavior at the FRP-to-masonry interface is a key factor affecting the flexural capacity as it is the means for transfer of stress between the FRP and the substrate to develop composite action. Although the beneficial effects of strengthening masonry structures with FRP materials have been demonstrated in the literature, the knowledge of the bond at the FRP-to-masonry interface is still relatively limited. To improve this understanding, this paper presents the results of a numerical investigation into the local behavior at the FRP-masonry interface. Two analytical procedures (i.e., a new generic numerical procedure and a closed-form mathematical solution) were developed to predict the global load-slip response of FRP-to-masonry pull tests by using various local bond-slip relationships. This study compares the effects of homogeneous and heterogeneous representations of the masonry substrate on the prediction of this global response and the influence of different bond-slip models and bond-slip parameters. The analytical results were validated against test data with both methods predicting the experimental behavior well. The paper concludes with recommendations regarding the influence of the heterogeneous nature of masonry and the effect of the bond-slip parameters on the load-slip response of FRP-to-masonry pull tests.