School of Civil Engineering, Liaoning Technical University, Fuxin, China.
PLoS One. 2021 Sep 20;16(9):e0255603. doi: 10.1371/journal.pone.0255603. eCollection 2021.
The reinforced concrete-filled steel tube (RCFST) column solves several of the problems of the concrete-filled steel tube (CFST) column in practical engineering applications. Moreover, RCFST has a simple joint structure, high bearing capacity, good ductility, and superior fire resistance. From a structural safety perspective, designers prioritize the creep performance of CFST members in structural design. Therefore, the creep behavior of RCFST columns should be thoroughly investigated in practical engineering design. To study the influence of the creep behavior of RCFST columns under axial compression, this work analyzed the mechanical behavior of composite columns based on their mechanical characteristics under axial compression and established a creep formula suitable for RCFST columns under axial compression. A creep analysis program was also developed to obtain the creep strain-time curve, and its correctness was verified by existing tests. On this basis, the effects of the main design parameters, such as the stress level, steel ratio, and reinforcement ratio, on the creep behavior were determined and analyzed. The creep of the tested composite columns increased rapidly in the early stages (28 days) of load action; the growth rate was relatively low after 28 days and tended to stabilize after approximately six months. The stress level had the greatest influence on the creep of RCFST columns under axial compression, followed by the steel ratio. The influence of the reinforcement ratio on the creep behavior was less. The results of this study can provide a reference for engineering practice.
钢管混凝土（RCFST）柱解决了实际工程应用中混凝土钢管（CFST）柱的几个问题。此外，RCFST 具有简单的节点结构、高承载能力、良好的延性和优异的耐火性能。从结构安全的角度来看，设计人员在结构设计中优先考虑 CFST 构件的徐变性能。因此，在实际工程设计中应彻底研究 RCFST 柱的徐变行为。为了研究轴压下 RCFST 柱的徐变行为的影响，这项工作基于轴压下的力学特性分析了组合柱的力学行为，并建立了一个适用于轴压下 RCFST 柱的徐变公式。还开发了一个徐变分析程序来获得徐变应变-时间曲线，并通过现有试验验证了其正确性。在此基础上，确定并分析了主要设计参数，如应力水平、钢率和配筋率对徐变行为的影响。测试的组合柱的徐变在荷载作用的早期（28 天）迅速增加；28 天后增长率相对较低，大约六个月后趋于稳定。应力水平对轴压下 RCFST 柱的徐变影响最大，其次是钢率。配筋率对徐变行为的影响较小。本研究的结果可为工程实践提供参考。
