Numerical simulation of debonding of CFRP strengthened steel beam

Abstract

Carbon Fiber Reinforced Polymer (CFRP) is an advanced engineering material introduced to aerospace industry, recently. Later, the applications of CFRP extended to other field as well. In Civil Engineering, CFRP is popular in retrofitting of damaged and deteriorated structures. Although the material has been successfully applied to concrete structures, applications in steel structures have been limited due to some drawbacks. One of such drawbacks is debonding of CFRP. In an effort to identify the factors affecting debonding, this study explored how the properties of adhesive could affect debonding. Non-linear finite element analysis was carried out for a 3D model of steel I girder subjected to four point bending. The model was validated using the experimental results available in the literature. CFRP laminate was attached to the bottom of the flange using three different types of adhesives having different material properties. The results of the numerical simulation showed that both the increment in load carrying capacity and the failure mode is affected by the properties of the adhesive significantly. As the shear strength and the elastic modulus of the adhesive increases, a considerable increase in the load carrying capacity is observed. However, the increment in load carrying capacity with respect to the increment in elastic modulus seems to become less significant as the elastic modulus increases. For example the increment in load carrying capacity per unit increment of elastic modulus between the first two adhesives is 3.7 kN while the same between the second and third adhesives is 0.21 kN. Also, the failure mode is found to be switched from below load point debonding (failure of the bond between the CFRP and adhesive) to below load point splitting (failure of CFRP plate in transverse direction) Therefore, it can be concluded that when designing a CFRP strengthening system for structural steel, considerable attention must be given to the adhesive properties as well