Fatigue sensitive details in aging steel girders is one of the common problems that structural engineers are facing today. The design characteristics of steel members can be enhanced significantly by epoxy bonding carbon fiber reinforced polymers (CFRP) laminates to the critically stressed tension areas. This paper presents the results of a study on the retrofitting of notched steel beams with CFRP patches for medium cycle fatigue loading (R=0.1). A total of 21 specimens made of S127×4.5 A36 steel beams were prepared and tested. Unretrofitted beams were also tested as control specimens. The steel beams were tested under four point bending with the loading rate of between 5 and 10 Hz. Different constant stress ranges between 69 and 379 MPa were considered. The length and thickness of the patch were kept the same for all the retrofitted specimens. In addition to the number of cycles to failure, changes in the stiffness and crack initiation and growth were monitored during each experiment. The results showed...

The demand for the use of carbon-fiber-reinforced plastics (CFRP) in rehabilitation of deteriorating infrastructure is increasing worldwide. The design characteristics of reinforced concrete or steel members can be enhanced significantly by epoxy bonding CFRP laminates to the critically stressed tension areas. There is, however, a concern regarding possible galvanic corrosion when carbon and steel are bonded together. This paper presents the result of a study on the galvanic corrosion between CFRP laminates and steel. A total of 38 specimens made of steel and carbon fibers were prepared and tested. Two simulated aggressive environments and three different amounts of epoxy coating were used in addition to samples with no coating at all. Furthermore, the effect of the sizing agent on the galvanic corrosion rate was investigated, and three different solvents were used to remove the sizing agents from the surface of the carbon fibers. Potentiodynamic polarization and galvanic corrosion tests were conducted. T...

The use of advanced composite materials for rehabilitation of deteriorating infrastructure has been embraced worldwide. The conventional techniques for strengthening of substandard bridges are costly, time consuming, and labor intensive. Many new techniques have used the lightweight, high strength, and the corrosion resistance of fiber reinforced polymers (FRP) laminates for repair and retrofit applications. The load-carrying capacity of a steel-concrete composite girder can be improved significantly by epoxy bonding carbon fiber reinforced polymers (CFRP) laminates to its tension flange. This paper presents the results of a study on the behavior of steel-concrete composite girders strengthened with CFRP sheets under static loading. A total of three large-scale composite girders made of W355×13.6 A36 steel beam and 75-mm thick by 910-mm wide concrete slab were prepared and tested. The thickness of the CFRP sheet was constant and a different number of layers of 1, 3, and 5 were used in the specimens. The t...

The aging infrastructure of the United States requires significant attention for developing new materials and techniques to effectively and economically revive this aging system. Damaged steel-concrete composite girders can be repaired and retrofitted by epoxy bonding carbon fiber-reinforced polymer (CFRP) laminates to the critical areas of tension flanges. This paper presents the results of a study on the behavior of damaged steel-concrete composite girders repaired with CFRP sheets under static loading. A total of three large-scale composite girders made of W355×13.6 A36 steel sections and 75-mm-thick by 910-mm-wide concrete slabs were prepared and tested. One, three, and five layers of CFRP sheet were used to repair the specimen with 25, 50, and 100% loss of the cross-sectional area of their tension flange, respectively. The test results showed that epoxy bonded CFRP sheet could restore the ultimate load-carrying capacity and stiffness of damaged steel-concrete composite girders. Comparison of the experimental and analytical results revealed that the traditional methods of analysis of composite beams were conservative.