Design of Adehsive Joints in FRP-Bonded Steel Beams

The use of bonded carbon fiber-reinforced polymer (CFRP) laminates to strengthen and upgrade existing structures has attracted a great deal of attention during the past two decades. Fiber-reinforced polymer (FRP) bonding has been widely researched and practiced in the strengthening of concrete members. However, when it comes to steel structures, it is somewhat limited in terms of field applications. One of the most important obstacles to the widespread use of FRP bonding in steel structures is the lack of design codes. This is mainly due to the lack of suitable design models for adhesive joints used to bond FRP laminates to steel substrates. Issues such as the lack of knowledge about the behavior of adhesive joints, the lack of suitable material models for structural adhesives, and analyzing adhesive joints are contributing to the difficulty associated with establishing design models. This paper is mainly concerned with a proposal and verification of a new design model for adhesive joints used to bond FRP laminates to steel beams. The paper, first, shortly reviews the most commonly used failure criteria and presents the background to the newly proposed model. Quasi-static tests were then performed on steel plate and full-scale beam specimens bonded with CFRP laminates to evaluate the new design model. The new design model presented in this paper was found to be accurate in terms of predicting the ultimate load and failure mode of the joints. To illustrate the application of the new design model, an example is appended to this paper