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实际结构中受相邻构件的约束,火灾下构件内力与变形发生变化,将影响其耐火极限,但目前关于钢管混凝土柱抗火性能的研究大多针对单根柱,未考虑相邻构件产生的端部约束效应。为此,基于ABAQUS软件,建立了考虑端部轴向约束的圆钢管混凝土柱有限元模型,分析了轴向约束作用对其轴力、变形以及耐火极限的影响。研究结果表明,轴向约束作用显著影响柱的轴力,表现为膨胀阶段柱内力增加,压缩阶段内力减小,进而使得变形减小,耐火极限提高。此外,分析了截面尺寸、荷载比、长细比以及偏心率对考虑端部轴向约束作用的钢管混凝土柱耐火极限的影响。结果表明,对于轴向约束刚度比0.02的圆钢管混凝土柱,当长细比在30以内时,轴向约束作用对耐火极限的提高幅度在10%~40%之间,可考虑约束作用对耐火极限的提高。与无端部约束柱类似,随着截面尺寸的增加、荷载比和长细比的减小,考虑端部约束的构件耐火极限也逐渐增大;而与无约束柱不同的是,偏心率对有端部约束的钢管混凝土柱的耐火极限影响较大。
Due to the constraint of adjacent components in the actual structure, the internal forces and deformation of the components under fire will change, which will affect the fire resistance. However, the research on the fire resistance of concrete filled steel tubular columns is mostly aimed at a single column, Department of restraint effect. Therefore, based on the ABAQUS software, a finite element model of CFST column considering axial restraint of the end was established and the influence of axial restraint on its axial force, deformation and fire resistance was analyzed. The results show that the axial restraint effect significantly affects the axial force of the column, which shows that the internal force of the column increases in the expansion stage and the internal force decreases in the compression stage, which further reduces the deformation and increases the fire resistance. In addition, the influence of cross-sectional size, load ratio, slenderness ratio and eccentricity on the fire resistance of concrete-filled steel tubular columns considering end-axial restraint was analyzed. The results show that when the slenderness ratio is less than 30, the axial restraint effect on the CFST column with axial restraint stiffness ratio of 0.02 is increased by 10% ~ 40%, and the restraint effect on the fire resistance Increase the limit. Similar to the unrestrained restraint columns, the load-bearing ratio and the slenderness ratio decrease with the increase of the section size, and the fire resistance of the component with the restrained end increases gradually. However, unlike the unconstrained columns, The confined concrete-filled steel tube columns have a greater impact on the fire resistance.