Behavior and Performance of Fiber-Reinforced Polymer-to-Steel Bond

This paper presents a detailed discussion of bond behavior and fatigue, which have a major, often overlooked, impact on the long-term performance of steel bridges strengthened with fiber-reinforced polymer (FRP) materials. The paper discusses the primary factors that affect the bonding behavior between steel and FRP materials. The mechanisms of bonding are highlighted, and the main factors that contribute to the environmental degradation of bonds are outlined. Techniques to produce high-quality, durable, and reliable bonds are presented; these techniques include surface preparation techniques, use of primers, and use of various plate end details to reduce bond stress concentrations and mitigate debonding. Various factors that affect the fatigue performance of FRP materials and structural adhesives are enumerated, and the behavior of FRP patches used to repair cracked steel members is described. This paper highlights some complexities and nuances associated with the design and installation of an FRP-based retrofit system for steel bridges and structures and some key practices that should be adopted to ensure the effective and reliable performance of the retrofit.