To better understand the mechanical property issues of in-service concrete-filled steel tube (CFST) bridges susceptible to natural environmental temperatures, 13 CFST stub columns were assessed under axial compression with different ambient temperatures and steel ratios, with the strength of the core concrete as the main parameters. The influence of ambient temperature on the peak strain and joint elastic modulus of the CFST stubs was investigated. The influence mechanism of steel content and core concrete strength on the residual toughness of the CFST at different ambient temperatures was revealed. In this study, we proposed a modified constitutive equation for CFST, taking into account the ambient temperature. We demonstrated that the peak strain, residual toughness ratio, and elastic modulus of the CFST stubs significantly decreased when the temperature decreased. The calculated values of the modified constitutive equation for CFST, taking into account the ambient temperature, were in good agreement with the test results and could be used to predict the trends in stress properties of the CFST stubs at different temperatures. The results could serve as a critical reference for the design and calculation of CFST structures in very cold regions.

中文翻译：

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不同环境温度下钢管混凝土短柱轴压性能试验研究

为了更好地了解在役钢管混凝土桥梁易受自然环境温度影响的力学性能问题，对13根钢管混凝土短柱在不同环境温度和钢材配比下的轴压状态下进行了评估，并评估了核心混凝土的强度作为主要参数。研究了环境温度对钢管混凝土短截线峰值应变和接头弹性模量的影响。揭示了不同环境温度下含钢量和核心混凝土强度对钢管混凝土残余韧性的影响机制。在本研究中，我们提出了一种修正的钢管混凝土本构方程，考虑了环境温度。我们证明，当温度降低时，钢管混凝土短截线的峰值应变、残余韧性比和弹性模量显着降低。考虑环境温度的修正钢管混凝土本构方程的计算值与试验结果吻合较好，可用于预测不同温度下钢管混凝土短柱的应力特性变化趋势。研究结果可为严寒地区钢管混凝土结构的设计和计算提供重要参考。