方钢管配筋混凝土柱耐火极限的计算

Calculation of Fire Resistance for Bar-reinforced Concrete-filled Square Steel Tubular Columns

合理确定了高温下钢材和混凝土的热工参数和热-力本构关系,根据构件截面温度场分布,提出了计算火灾下方钢管配筋混凝土柱力学性能的理论分析模型,模型中考虑了钢材的高温蠕变、混凝土的瞬态热应变和高温徐变,计算结果得到了以往实验结果的验证。在此基础上,分析了配筋率和钢筋屈服强度对方钢管配筋混凝土柱耐火极限的影响规律。结果表明,对于专门考虑抗火作用钢筋的构件,配筋率1%～5%可比钢管素混凝土柱耐火极限提高约10%～60%,构件的耐火极限随钢筋屈服强度的增加而稍有增长。对于荷载比已包含钢筋受力作用的构件,配筋率和钢筋屈服强度对耐火极限的影响很小。

The thermal properties and the thermo-mechanical constitution laws of steel and concrete under high temperature are conformed.According to the section temperature distribution,the theoretical model is presented to calculate the fire behavior of bar-reinforced concrete-filled square steel tubular columns.The transient strain of concrete,creep strain of steel and concrete under fire are taken into consideration in the model.The calculated results agree well with previous experimental results.Based on the theoretical model,the influences of steel reinforcement ratio and strength on fire resistance of the members are analyzed.The results show that,for the members with special consideration of fire resistant bars,the fire resistance with the reinforcement ratios from 1% to 5% is approximately 10% to 60% higher than that of the concrete-filled steel tubular columns.The fire resistance rises slightly with the increase of reinforcement strength.For the members with the load level including force action of reinforcement,the steel reinforcement ratio and strength have little influence on fire resistance.