Experiments on the flexural behavior of full-scale PC box girders with service damage strengthened by prestressed CFRP plates.

• In-situ strengthening construction and experimental study were conducted on full-scale PC box girders derived from a bridge with typical damage accumulated from 20 years of service duration. • The hybrid strengthening measures including prestressed CFRP plates could effectively improve both the serviceability and ultimate limit states for PC box girder bridge. • The CFRP plate area was recommended for the bridge strengthening design, and analytical solutions were derived to calculate the yielding and ultimate flexural capacity of strengthened PC box girder. Two full-scale PC box girders with typical damage were derived from an in-situ bridge that was in service about 20 years, to understand the strengthening effects of prestressed CFRP plates for the entire bottom slab, casting of a RC layer in composite action with the entire top slab and steel plates anchored on the webs of the shear span. The flexural tests were conducted on the two full-scale PC box girders with and without strengthening measures, and comparative analysis was conducted regarding flexural capacity, failure mechanism, rigidity, ductility and overall structural behavior. The test results showed that the strengthening measures improved the girder rigidity by 40 % before reaching cracking state and increased the yielding and ultimate capacity by 39 % and 28% respectively. The theoretical analysis was conducted to discuss failure modes for PC box girder strengthened by prestressed CFRP plates. Theoretical equations are derived to calculate the flexural capacity of strengthened PC box girder according to typical failure modes. Good agreement with tested results was obtained. The strengthening design of the prestressing CFRP plate was verified by application in a PC box girder bridge. [ABSTRACT FROM AUTHOR]