Long-term behavior of the steel-concrete composite girder bridge with old and new concrete

In order to study the long-term behavior of the steel-concrete composite girder bridge with old and new concrete, the temperature and strain data of a simply supported steel-concrete composite girder bridge were collected for two years by field test. A refined calculation method (AEMMold-new) was proposed based on the age-adjusted effective modulus method (AEMM) to calculate the shrinkage and creep stress of the composite bridge with old and new concrete. Finally, the shrinkage and creep stresses of the wet joint, concrete deck and steel girder calculated by AEMMold-new were compared to the tested values. The results showed that the creep degree of the concrete can be great influenced by the initial loading ages. The stresses of the concrete deck, wet joint and the steel girder are compressive stresses under the shrinkage and creep effects, and the trend of these stresses are all gradually increase at first and then tend to be stable. The final stresses do not exceed 40 % of the strength. The stress change of the upper flange of the steel girder is similar to the concrete deck due to the upper flange is close to the concrete deck, while the stress of the lower flange of the steel girder is greatly influenced by the environment, and in a larger change range. The average error between the calculated shrinkage and creep stress of the wet joint and concrete deck by AEMMold-new and the tested average stress are both about 15 %, while the average error of the steel girder is about 8 %. The average error is relatively large between the calculated stress by AEMM and the tested average stress, while the accuracy of the AEMMold-new has been further verified by comparing to other studies, and the error is basically not more than 10%. Therefore, it can be considered that the shrinkage and creep effects of the bridge can be better calculated by AEMMold-new.