Damage and Failure Analysis of FRP Strengthened RC Beams with Openings

Abstract

In the real world, openings are often needed in RC beams for the passage of ducts or pipes. If these openings are designed prior to construction, adequate reinforcement can be provided as a preventive measure. However, if these openings are carved after construction, these openings lead to a significant decrease in the ultimate load and stiffness due to the reduction of the cross-sectional area of the concrete and the existing steel reinforcement. In such cases, externally bonded (EB) fiber-reinforced polymer (FRP) can be used to strengthen the weakened beam. Finite element analyses of RC beams are performed in this study using ABAQUS to investigate the effect of open-ings on flexural behavior. The present FE approach examines the behavior of the RC beams under different structural conditions, taking into account material nonlinearity. The existing numerical models also do not consider damage in FRP. The present FE approach incorporates damage in con-crete through the concrete damage plasticity model and simulates failure of FRP sheets using a pro-gressive damage model based on Hashin damage criteria developed using a user-defined subroutine VUMAT. In this study, parametric analyses on different FRP lengths, thicknesses, and lamination schemes are carried out using the developed finite element modelling technique to find an efficient FRP strengthening system for the weakened RC beam with an opening. The study highlights that the proposed FRP strengthening system is effective when sufficient sheet length and proper fiber orientation are provided, while an increase in the thickness offers limited benefit as it suffers from premature debonding. The developed numerical modelling technique can accurately analyze RC beams with openings, and the results from the present analysis will be useful for design recommen-dations and practical applications.