In order to study the durability degradation characteristics of concrete box girder under load and carbonation and chloride ion erosion, a scale model of concrete box girder was made for experimental research. According to the test results, the diffusion characteristics of chloride ions in the concrete box girder under the coupling effect of load and carbon dioxide were analyzed. By revising the calculation formula of the existing chloride ion concentration considering multiple factors, a calculation model of chloride ion concentration considering the influence of carbonation was proposed, and the test results were verified. The results show that the chloride concentration of the box girder on the same cross section is non-uniformly distributed due to the shear lag effect and the spatial structure. After considering the effect of carbonation, the difference rate of the improved model proposed in this paper is generally within 10%. Compared with the original model, the difference rate is reduced by a maximum of 19%.
Remarkable performance of glass fiber-reinforced polymer (FRP) bars make it an ideal candidate for prolonging the life of concrete structure. Although analytical and experimental research of concrete beams strengthened by FRP have flourished in recent decades, it is still in lack of research in comparison with traditional reinforced concrete structures, especially in case of the flexural behavior. In this paper, two groups of GFRP reinforced concrete slabs with different strength grades and reinforcement ratios were experimentally tested, and theoretical calculation method on their bearing capacities was explored. By comparing the deformation and bearing capacity characteristics, the test results were discussed in detail. The calculation formula of flexural capacity of GFRP reinforced concrete slab was derived and then verified against the experimental data. The test results show that the load deflection curve presents obvious double straight lines, and the reinforcement ratio is not closely related to the initial crack load. The cross section still obeys the plane section assumption and the crack distribution is sparse with large width. The flexural bearing capacity coefficient changes from 1.02 to 1.36. Therefore, the limitation of 1.4 times balanced reinforcement ratio in ACI is verified, which could apply a valuable reference for durability design of GFRP reinforced concrete slabs.
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