Modelling of flexural behaviour of RC beams strengthened with NSM CFRP rods including serviceability

Abstract

The proposed model calculates the deflection of carbon fibre-reinforced polymer (CFRP) strengthened beams. In this model, the beams were strengthened before loading, so in an uncracked state. The calculation before cracking uses conventional existing models. The calculation of the deflection after cracking is based on a non-linear Macro-Finite-Element (M.F.E.). This M.F.E. is a beam Finite Element characterised mainly (for the bending problems) by its homogeneous average moment of inertia. The typical global behaviour of beams strengthened by NSM rods s was modelled as well as repeated loading cycles. The model is validated experimentally on two CFRP strengthened concrete beams with two sections of CFRP rods subjected to four-point flexure under repeated loading cycles after cracking and then a constant loading rate until failure. Results show that the model gives good predictions of the bending stiffness of the beam during the loading cycle and the permanent residual deflection after unloading due to crack propagation.

Keywords:

• FRP rods
• NSM reinforcement
• service loading
• non-linear Macro-Finite-Element
• tension stiffening