Flexural and Interfacial Behavior of Externally Bonded/Mechanically Fastened Fiber-Reinforced Polymer-Strengthened Reinforced Concrete Beams

The determination of structural behavior requires advanced numerical methods, of which results are substantiated by credible experimental findings. This research aims to create precise finite element models for fiber-reinforced polymer (FRP)-strengthened concrete beams. The models are developed to assess the flexural and interfacial types of behavior of beams strengthened using three different schemes; namely, externally bonded (EB), mechanically fastened (MF), and hybrid EB/MF FRP systems. The interfacial behavior between the EB, MF, and hybrid EB/MF FRP and the concrete is accounted for using specially developed interface elements. A user-defined subroutine for the microplane constitutive law for concrete is incorporated in the model. Results are presented in terms of the ultimate load capacities, load-deflection relationships, and interfacial stress distributions. Numerical results are validated against published experimental results, and show reasonable agreement. Models for hypothetical cases are created to enrich the discussion on the interfacial stress distributions.