Numerical and experimental validation of FRP patch anchors used to improve the performance of FRP laminates bonded to concrete

Numerical simulations using the nonlinear finite-element method (FEM) have been successfully used to predict the full nonlinear response of reinforced concrete (RC) members strengthened with fiber-reinforced polymers (FRPs). Calibrated numerical models have the potential to reduce the number of experimental tests through the use of parametric studies that can provide further data on the influence of key parameters. A relatively new area of research is the use of FRP anchorage systems to improve the efficiency of FRP-strengthened members by preventing the various modes of deboning failure. Although FRP anchorage systems have shown exceptional potential for widespread use, further experimental and numerical data are required before establishing theoretical models and design guidelines. The focus of the present work is to develop and validate an FE modeling approach to expand the available data on FRP-to-concrete joints anchored using unidirectional and bidirectional fiber patch anchorages. The critical bond properties among multiple layers of FRP sheet, laminate, and concrete are simulated using interface elements and a calibrated interface bond law. The proposed modeling approach and calibration techniques have resulted in replication of prepeak and postpeak response with a reasonable level of accuracy. Numerical parametric studies have also been conducted to expand the experimental data to encompass variations in concrete strength and the overall effect on anchorage effectiveness