| In the long-term service process of steel structures,due to the deterioration of the material’s performance or the severe environmental erosion,the demand for its repair and reinforcement is increasing.Carbon Fiber Reinforced Polymer(CFRP)has the advantages of light weight,high strength,corrosion resistance and fatigue resistance.The use of adhesive to reinforce CFRP to repair damaged steel structures can effectively improve the bearing capacity and service life of the original structure.As the CFRP-steel interface is a weak point of the reinforced structure,coupled with the unavoidable overload damage and erosion in the hot and humid environment in actual service,the interface bonding performance has become a key link for CFRP-reinforced steel structures.In this paper,tensile tests of CFRP-steel single-shear specimens and interface microscopy experiments based on scanning electron microscopy are designed.The main contents and conclusions are as follows:(1)Tensile test study of single-shear specimen of CFRP-reinforced steel plate.Considering the factors of overload damage and hot and humid environment,through the single-sided shear test,a comparative analysis of the failure modes of specimens under different working conditions,the axial strain distribution of CFRP plates,the distribution of shear stress,and the bond-slip relationship.The results show that the overload damage and the hot and humid environment have adverse effects on the CFRP-steel interface bearing capacity,peak shear stress,bonding stiffness and fracture energy.The influence of the hot and humid environment is more obvious.Compared with undamaged specimens,the ultimate load reduction rates of overload damaged specimens,wet heat cycling specimens,overload damaged and wet heat cycling specimens were 5.6%,8.2% and 12.3%.The peak interface shear stress decreased by 19.1%,24.9%,and 28.5%,respectively.(2)Microscopic interface study based on scanning electron microscope.By combining scanning electron microscope SEM and energy spectrometer EDS,the degradation laws of the bond properties of CFRP-steel interface under overload damage and wet and hot environment erosion were analyzed from the perspective of physical and chemical states,respectively.The results show that obvious large cracks appear at the interface of overload damage,the cracks are concentrated and the width is large;cracks and fine lines appear at the interface of damage in the hot and humid environment,and the cracks are widely distributed and small in width.Compared with the non-damaged specimen,the Si element in the overload-damaged specimen decreased slightly,and other major elements did not change much.In the hot and humid environment,the enrichment zone of O and Cl appeared at the intersection of cracks,and the apparent concentration increased from 0.34 and 0.01 to 6.42 and 0.24,respectively.At the same time of overload damage and moist heat environment,the elements C and Si decreased,and the elements O,Fe and Cl increased by 0.14,6.88 and 8.98 times,respectively.(3)Construction of CFRP-steel interface bond slip constitutive model in hot and humid environment.Based on the analysis and discussion of the existing model,combined with the characteristics of the test data,the curve results were finally fitted based on the Popovics formula,and an empirical formula for interface bonding slip in a hot and humid environment was proposed.The results show that the model considers and corrects the influence of wet and hot age on the interface-slip relationship at the interface,and can accurately predict the bond-slip relationship at the CFRP-steel interface in the hot and humid environment. |
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