This paper applied a thermal-mechanical sequential coupled mesoscopic simulation method to explore the axial compression performance and the corresponding size effect of Reinforced Concrete Columns confined by Stirrups (i.e., RCCS) at low temperatures, with considering the interaction between concrete meso-components and steel bars as well as the low-temperature effect of mechanical parameters. Based on the heat conduction analysis, the axial compression mechanical failure behavior of RCCS with four structural sizes (i.e., 267 × 267 × 801, 400 × 400 × 1200, 600 × 600 × 1800 and 800 × 800 × 2400 mm) and two stirrup ratios (i.e., 1.26% and 2.89%) at different temperatures (i.e., T = 20, −30, −60 and −90°C) was subsequently simulated. The effects of temperature, structural size and volume stirrup ratio on axial compression properties were quantitatively discussed. The results showed that the peak strength of RCCS increased with the decreasing temperature, and the smaller-sized RCCS showed a stronger effect of low-temperature enhancement. Both the residual strength and displacement ductility coefficient decreased with the decreasing temperature. The peak strength, residual strength and displacement ductility coefficient of RCCS decreased with the increasing structural size, showing obvious size effects. The size effect on peak strength increased with the decreasing temperature, (the maximum increase was nearly 140%), but the size effect on displacement ductility coefficient decreased (the maximum decrease was nearly 70%). The peak strength, residual strength and ductility were enhanced with the increasing volume stirrup ratio, which was helpful to reduce the influence of size effect. Finally, an improved size effect theoretical model was proposed, which can effectively predict the axial compressive strength of RCCS with different structural sizes and stirrup ratios at room and low temperatures. The present research results can provide reference for the large-scale engineering application of RCCS in low-temperature environments.

中文翻译：

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低温下 RC 柱轴压破坏的尺寸效应模型


本文采用热-机械顺序耦合细观模拟方法，探讨了箍筋约束钢筋混凝土柱（即 RCCS）在低温下的轴压性能和相应的尺寸效应，同时考虑了混凝土细观构件与钢筋之间的相互作用以及力学参数的低温效应。基于热传导分析，随后模拟了四种结构尺寸 （即 267 × 267 × 801、400 × 400 × 1200、600 × 600 × 1800 和 800 × 800 × 2400 mm）和两种箍筋比 （即 T = 20、-30、-60 和 -90°C） 下的轴向压缩机械破坏行为。定量讨论了温度、结构尺寸和体积箍筋比对轴压性能的影响。结果表明，RCCS 的峰值强度随着温度的降低而增加，较小尺寸的 RCCS 表现出更强的低温增强效果。残余强度和位移延性系数均随温度的降低而降低。RCCS 的峰值强度、残余强度和位移延性系数随着结构尺寸的增大而减小，表现出明显的尺寸效应。尺寸效应对峰值强度的影响随温度的降低而增大（最大增幅接近140%），但尺寸效应对位移延性系数的影响减小（最大降幅接近70%）。随着体积箍筋比的增加，峰值强度、残余强度和延性均增强，有助于减小尺寸效应的影响。 最后，提出了一种改进的尺寸效应理论模型，该模型可以有效预测不同结构尺寸和箍筋比的 RCCS 在室温和低温下的轴向抗压强度。研究结果可为 RCCS 在低温环境下的大规模工程应用提供参考。