【摘要】 采用大型有限元软件M SC.M ARC.M en tat,对具有轴向约束且无保护层的钢结构柱进行了非线性有限元分析,研究了不同轴向约束对钢结构柱抗火能力的影响,给出了典型约束钢结构柱的有限元网格划分和受压后的变形图,以及不同温度、不同约束刚度情况下的荷载-位移曲线,有限元数值模拟结果与试验进行对比,吻合较好.研究表明:室温下,轴向约束有利于提高柱子的极限承载能力,但在高温情况下,约束刚度的大小对柱子的抗火承载力却具有负面影响,轴向约束的提高降低了高温下柱子的极限承载力,并降低了柱子的极限温度承载力;在温度达到450℃之前,由于钢材的弹性模量改变与构件热膨胀而导致承载力的降低,温度超过450℃之后,弹性模量与屈服极限的折减,以及构件热膨胀所导致的约束反力共同作用使得构件更早失效.更多还原

【Abstract】 The finite element method(FEM) analysis for the fire resistance of unprotected steel column is conducted with utilization of MSC.MARC.Mentat.The effect of axial restraint stiffness on fire resistance of steel column is analyzed.The figures of the classic FEM model and deformation at failure are presented,and the load-deformation curves of steel column with different restraint stiffness at different elevated temperature are obtained.The FEM results are fairly close to test results.The analytical results show that although raising axial restraint stiffness can benefit load bearing of steel column in ambient temperature condition,but in fire condition,fire resistance of steel column is decreased as restraint stiffness increases.Under fire condition,the reduction of elastic modulus and thermal expansion of column result in the decrease of load-bearing capacity before the temperature arrives at 450℃;after it exceeds 450℃,the yield strength of steel begins to decrease and the high temperature leads to high reaction of axial restraint,finally leads to the column collapse in fire.更多还原