Behaviour of corroded reinforced concrete beams repaired with NSM CFRP rods, experimental and finite element study

Abstract

The near surface mounted reinforcement (NSM) technique is one of the promising techniques used nowadays to strengthen reinforced concrete RC structures. In the NSM technique, the Carbon Fibre Reinforced Polymer (CFRP) rods are placed inside pre-cut grooves and are bonded to the concrete with epoxy adhesive. This paper investigates corroded RC beams repaired with NSM CFRP rods and studies the failure mode of the repaired beam according to experimental and numerical modelling results. Experimental results and numerical modelling results of a 2D finite element (FE) model using the FEMIX computer code were obtained on five, 3-m-long beams: three corroded RC beams that had been exposed to natural corrosion for 25 years and two control beams with no corrosion. Two beams, one corroded and one control (A1CL3-R and A1T-R) were each repaired in bending with one 6-mm-diameter NSM CFRP rod and were then tested in three-point bending up to failure. The corrosion of the tensile steel bars and steel stirrups was studied. Ultimate capacity, yielding capacity and failure modes are also discussed. The experimental results showed that the NSM technique increased the overall capacity (ultimate load capacity and yielding capacity) of control and corroded beams despite a non-classical mode of failure with separation of the concrete cover occurring in the corroded beam due to damage induced by corrosion. The FE numerical modelling results from FEMIX were compatible with the experimental ones except for the repaired corroded beam A1CL3-R, for which a three-dimensional model using the commercial software ABAQUS was required. Finally some comparisons were made between the experimental and FE numerical modelling results obtained using ABAQUS in order to study the specific mode of failure of the corroded beam, which occurred by the separation of concrete cover.