Nonlinear 3D finite element modeling of RC beams strengthened with prestressed NSM-CFRP strips

This paper demonstrates a comprehensive 3D nonlinear Finite Element (FE) analysis of Reinforced Concrete (RC) beams strengthened with prestressed Near-Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) strips. Debonding effect at the epoxy-concrete interface was considered in the model by identification of fracture energies of the interfaces and appropriate bilinear shear stress-slip and tension stress-gap models. Prestressing was applied to the CFRP strips by adopting the equivalent temperature method. A constitutive confined concrete model for flexural member was generated from unconfined concrete curve and assigned to the concrete materials. The results from the FE model were validated with experimental data available in the literature. Comparison between FE and test results confirms excellent accuracy of the proposed model. An optimum prestressing level in the NSM-CFRP strips was determined that enhances the beam performance under service and ultimate loads by maintaining the amount of energy absorption in the strengthened beam equal to the un-strengthened control beam.