Wang Gaoxiong, Bao Yanhong, Yang Li, Yu Yang
School of Civil Engineering, Qinghai University, Xining 810016, China.
Qinghai Provincial Key Laboratory of Energy-Saving Building Materials and Engineering Safety, Qinghai University, Xining 810016, China.
Materials (Basel). 2021 Sep 24;14(19):5541. doi: 10.3390/ma14195541.
Based on the finite element (FE) analysis software Abaqus, an FE model of square-cased square steel tube reinforced concrete (ST-RC) columns under the hybridized action of high-temperature and load is established. The accuracy of the FE model is verified using experimental data from existing studies. This model is used to analyze the temperature change, internal force distribution, and failure characteristics of the square-cased square ST-RC columns under the action of fire, as well as the factors affecting the fire resistance limit of the column. The results of FE analysis show that under the action of fire, the maximum internal temperature of the square-cased square ST-RC columns occurs in the corner of the section. Moreover, the stress and strain reach their maximum values at the concrete corner outside the tube. During the heating process, an internal force redistribution occurs in the square-cased square ST-RC column. At the same time, the proportion of the axial force and the bending moment of the reinforced concrete outside the pipe decreases gradually, while the proportion of the internal force of the core concrete-filled steel tube (CFST) increases gradually. In essence, it is a process of load transfer from the high-temperature to the low-temperature zone. In addition, the section size, load ratio, slenderness ratio, cross-sectional core area ratio, steel content, and external concrete strength are the main parameters affecting the fire resistance limit of the square-cased square ST-RC columns. Among them, the cross-sectional core area ratio, section size, steel ratio, and external concrete strength are positively correlated with the fire resistance limit of the composite column. On the contrary, with the increase in the load ratio and the slenderness ratio, the fire resistance limit of the square-cased square ST-RC columns decreases. On this basis, a simplified formula to calculate the fire resistance limit of square-cased square ST-RC columns is proposed. The research results can be used as a theoretical reference for the fire protection design of this kind of structure in practical engineering.
基于有限元（FE）分析软件Abaqus，建立了方形套方形钢管混凝土（ST-RC）柱在高温与荷载共同作用下的有限元模型。利用现有研究的试验数据验证了该有限元模型的准确性。此模型用于分析方形套方形ST-RC柱在火灾作用下的温度变化、内力分布及破坏特征，以及影响柱耐火极限的因素。有限元分析结果表明，在火灾作用下，方形套方形ST-RC柱的截面角部出现最高内部温度。此外，应力和应变在钢管外部的混凝土角部达到最大值。在升温过程中，方形套方形ST-RC柱发生内力重分布。同时，钢管外钢筋混凝土的轴力和弯矩比例逐渐减小，而核心钢管混凝土（CFST）的内力比例逐渐增大。本质上，这是一个荷载从高温区向低温区转移的过程。此外，截面尺寸、荷载比、长细比、截面核心面积比、含钢量及外部混凝土强度是影响方形套方形ST-RC柱耐火极限的主要参数。其中，截面核心面积比、截面尺寸、含钢率及外部混凝土强度与组合柱的耐火极限呈正相关。相反，随着荷载比和长细比的增大，方形套方形ST-RC柱的耐火极限降低。在此基础上，提出了方形套方形ST-RC柱耐火极限的简化计算公式。研究结果可为实际工程中此类结构的防火设计提供理论参考。
