Bridges, Tunnels and other Transportation Structures
Steel girders in bridges are prone to fatigue damage over time. Railway bridges are susceptible to fatigue cracks in different elements. Frequent damage cases in which fatigue cracking occurs can have a primary load-action or deformation-induced nature, as will be discussed. Applying CFRP to the cracked area reinforces the beam and is currently one of the most cost-efficient methods for handling cracked steel members. The CFRP repairs the fatigue damaged steel beams in three ways: by reducing the stress range around the crack tip, by reducing the crack opening displacement, and by promoting the closure of the crack. The fatigue behavior of cracked I-section steel beams reinforced by using ultra-high modulus CFRP plates (UHM-CFRP) is illustrated. The use of UHM-CFRP plates bonded on the cracked steel beam, in fact, allows reducing the fatigue crack growth and extends the relevant fatigue life. A total of five steel beams were considered and an initial crack was created by notching the tension flange and part of the web. The cracked steel beams were then reinforced by bonding UHM-CFRP plates to the bottom side of the tension flange. Fatigue tests under constant amplitude bending loads were finally performed to investigate the fatigue behavior of the reinforced steel beams. Additionally, only few numerical models were developed to predict the fatigue behavior of steel beams repaired with CFRP materials.