火灾中带裂缝钢筋混凝土梁承载力算法研究

Calculation method of bearing capacity of reinforced concrete beam with cracks under fire

火灾中带裂缝钢筋混凝土梁的承载能力研究可为工程实际应用提供参考。文章利用有限元分析软件ABAQUS对火灾中带裂缝钢筋混凝土梁内部的温度场进行分析,阐明了火灾中带裂缝钢筋混凝土梁内部温度场的分布规律,根据其分布规律确定了在不同耐火时刻有裂缝钢筋混凝土梁300和800℃的等温线,结合已有的高温下钢筋混凝土梁承载力计算公式,提出了火灾中带裂缝钢筋混凝土梁承载力计算公式。结果表明：在同样的受火条件下有裂缝时钢筋混凝土梁中钢筋位置的温度比是无裂缝时钢筋混凝土梁中钢筋位置的温度高55%~144%;有五条裂缝的钢筋混凝土梁中钢筋位置的温度比有一条裂缝的钢筋混凝土梁中钢筋位置的温度高2.7%~11.5%;带裂缝钢筋混凝土梁的承载力比无裂缝钢筋混凝土的承载力低47%~82%。

In this paper,the capacity formulas of reinforced concrete beam with cracks under fire are proposed to study the effect of cracks on reinforced concrete structure,providing the reference for structural fire design. This paper presents a calculation method of reinforced concrete beam with cracks under fire. The temperature field calculation of the reinforced concrete beam with cracks under fire is achieved by ABAQUS. According to the results,isothermal of 300 ℃ and 800 ℃ is achieved.Combined with the calculation formula of reinforced concrete beam under the fire,the ultimate bearing capacity formulas of reinforced concrete beam with cracks are created. By using a case,the result of reinforced concrete beam with cracks and without cracks is obtained. The results indicate that the beam with cracks is 50% ~ 144% higher than that without cracks under the same conditions,and the beam with five cracks is 2. 7% ~ 11. 5% higher than that with one crack. The results can be obtained that the bearing capacity of beam with cracks is 47% ~ 82% less than that without cracks.