Carol Shield, Principal Investigator

Repair of Fatigued Steel Bridge Girders With Carbon Fiber Strips

Several years ago, it was common for steel cover plates to be welded to flanges of hot-rolled steel girders in high moment regions in order to increase the cross section. These cover plates were terminated in negative moment regions, and welds at the ends of cover plates resulted in stress concentrations in the flange. After years in service, these stress concentrations have been causing fatigue cracks, and some rehabilitation schemes for these cracks have been proposed.

This research focused on carbon fiber reinforced polymer (CFRP) strips bonded to the tension flange as the rehabilitation method for those fatigued tension flanges. In order to use the CFRP strips as the rehabilitation method, it was necessary to find the development length of the adhesive so that the adhesive can transfer sufficient forces from tension flange to the CFRP strips. A series of small-scale experimental tests were conducted to define the development length. The stress distribution in the adhesive of experimental specimens must be similar to that in the rehabilitated girder. Finite element analysis using abaqus enabled the researchers to compare those two stress distributions, and to decide which test set-ups can be used. Through preliminary studies, it was found that a large amount of computation time was required to analyze the stress concentration in adhesive, not only due to a singularity at the crack tip but also because of a material non-linearity caused by the high stress concentration.

Research Group and Collaborator

Jerome F. Hajjar, Faculty Collaborator
Jessica Moeller, Graduate Student Researcher
Katsuyoshi Nozaka, Graduate Student Researcher