Predicting the Flexural Behaviour of CFRP-Strengthened Concrete Beam using Combined XFEM and Cohesive Zone Model

Abstract

This paper presents the numerical strength prediction of externally carbon fibre reinforced polymer (CFRP)- strengthened concrete beams using a traction-separation law. From reported experimental observations, the externally CFRP-strengthened concrete beams are prone to exhibit mixed-mode cohesive failure within the adhesive layer before beam separation. Testing series comprised of different strengthening schemes and CFRP plate length indicated that all specimens failed in cohesive delamination (debonding). This study performed a numerical modelling framework by using a combination of extended finite element method (XFEM) within the concrete beam and cohesive zone model (CZM) within the adhesive layer to explicitly demonstrate debonding phenomenon as seen in experimental observations. The results showed that the modelling technique was able to capture the debonding failure and the crack propagation of the concrete beam, consistent with experimental observations. Hence, the combination of the XFEM-CZM approach yields good agreements with experimental datasets. It was found that discrepancies of maximum load-bearing capacity between numerical modelling and previous experimental work are below 17 % were found in all testing series. However, due to the unavailability of fracture energy properties of tested concrete, the current approach used values of similar concrete grade from other literature. It is expected that better results would be obtained if the fracture energy of the investigated concrete beam was independently measured.

Keywords

• bilinear traction-separation laws
• combination of xfem and czm
• externally normal beam strengthening
• cfrp
• four-point bending test
• debonding failure