Finite-element modelling of RC beams with carbon FRP strengthened web openings

Abstract

Web openings are commonly used in reinforced concrete (RC) beams to accommodate pipes, ducts, and utilities. The expected reduction in strength can be compensated by locally strengthening the beam opening with carbon fibre-reinforced polymer (CFRP). In this paper, a robust non-linear finite-element model (FEM) is developed to simulate the behavior of RC beams with/without openings. The model can simulate the strengthening of the beam opening with CFRP sheets. The developed FEM is validated using seven simply supported RC beams that were previously tested under monotonic two concentrated loads. The crack pattern and load-deflection relationship, from the FEM, were compared to those obtained from the experiments. The developed FEM was utilised to conduct a parametric study on 32 beams to investigate the behavior of RC beams with CFRP strengthened openings. The parametric study showed that the opening width did not significantly affect the load at failure. However, both the opening depth and distance from support had a clear effect on the failure load. Increasing the stirrups diameter from 8 to 10 mm increased the shear capacity of RC beams by 3–16%. The failure loads obtained from the proposed FEM were compared to those obtained from international design codes.