Study on Influence of Concrete Protective Layer on Mechanical Properties of Sleeve Grouting Connections After High-Temperature Exposure
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摘要: 套筒灌浆连接是目前装配式混凝土结构中受力钢筋主要的连接方式之一。为研究混凝土保护层对火灾高温后套筒灌浆连接力学性能的影响,对12个30 mm混凝土保护层套筒灌浆连接件及12个无保护层试件进行了火灾高温后单向拉伸和高应力重复拉伸试验,探索了混凝土保护层对不同加载条件下套筒灌浆连接件破坏模式、承载力和延性的影响规律。试验结果表明:混凝土保护层对高温后套筒灌浆连接失效模式影响显著,60 min火灾高温后,混凝土保护层试件在单向拉伸和高应力重复拉伸下均为钢筋拉断破坏,无保护层试件表现为黏结失效破坏;高温后,混凝土保护层能提高套筒灌浆连接件在两种加载方式下的极限荷载和延性,但混凝土保护层试件在高应力重复拉伸下的极限荷载和延性略低于单向拉伸。在试验的基础上,采用有限元软件ABAQUS建立了数值模型,以混凝土保护层厚度和受火时间为参数展开分析。有限元分析结果表明:混凝土保护层厚度、受火时间对试件的极限荷载和黏结强度具有显著影响,试件的极限荷载和黏结强度均随保护层厚度的增大而提高,并随受火时间的延长而降低。基于试验和有限元分析结果,提出了考虑混凝土保护层厚度和受火时间共同影响的套筒灌浆连接极限黏结应力计算方法。Abstract: Sleeve grouting connections are one of the primary connection methods for reinforcing steel in prefabricated concrete structures. To investigate the effect of concrete cover on the mechanical properties of sleeve grout connections after exposure to high temperatures from fire, 12 sleeve grout connection components with a 30 mm concrete cover and 12 specimens without a concrete cover were subjected to uniaxial tensile and high-stress repeated tensile tests after high temperatures exposure. The study explored the influence of the concrete cover on the failure mode, load-bearing capacity, and ductility of sleeve grout connection components under different loading conditions. The test results indicated that the concrete cover had a significant impact on the failure mode of sleeve grouting connections after exposure to high temperature. After 60 minutes of exposure, the specimens with concrete covers exhibited reinforcement breakage failure under both uniaxial tensile and high-stress repeated tensile test, whereas the specimens without concrete covers exhibited bond failure. After high-temperature exposure, the concrete protective layer enhanced the ultimate load and ductility of the sleeve grout connection under both loading conditions, but the ultimate load and ductility of specimens with a protective layer under high-stress repeated tensile loading were slightly lower than those under uniaxial tensile loading. Based on the experiments, a numerical model was established using the finite element software ABAQUS, with concrete protective layer thickness and fire exposure time as the parameters. Finite element results indicated that the thickness of the concrete protective layer and exposure time significantly affected the ultimate load and bond strength of the specimens. Both the ultimate load and bond strength increased with increasing protective layer thickness and decreased with prolonged exposure time. Based on the experimental and finite element analysis results, a calculation method for the ultimate bond stress of sleeve grouting connections, considering the combined effects of protective layer thickness and exposure time, was proposed.
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