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高温荷载作用下钢材产生明显的蠕变变形,对钢结构在火灾下的变形和受力性能产生较大的影响。为定量确定高温蠕变对约束钢梁抗火承载力的影响,利用ANSYS建立了考虑蠕变的约束钢梁有限元分析模型。与试验数据对比发现:仅仅通过应力应变关系考虑蠕变不能较好地模拟约束钢梁中蠕变的发展,而采用Poh模型的应力应变关系并考虑蠕变与试验数据吻合最好。利用验证后的分析模型进行参数分析,发现转动约束刚度、屈服强度、升温速率和跨高比等都对约束钢梁的临界温度有明显的影响。《建筑钢结构防火技术规范》给出的约束钢梁抗火设计方法未充分考虑这些参数的影响。对参数分析的结果进行回归分析,给出了适用的考虑蠕变的约束钢梁抗火简化计算方法。
Steel under high temperature loads have obvious creep deformation, which has a great influence on the deformation and force performance of steel structure under fire. In order to quantitatively determine the effect of high temperature creep on the load-carrying capacity of confined steel beams, finite element analysis model of constrained steel beams considering creep was established by ANSYS. Compared with the experimental data, it is found that the creep can not well simulate the creep development in the confined steel beam simply by considering the stress-strain relationship. The stress-strain relationship of the Poh model and considering the creep agree well with the experimental data. After analyzing the parameters with the verified analytical model, it is found that the rotational restraint stiffness, yield strength, heating rate and span ratio all have obvious influence on the critical temperature of the confined steel beam. The Fire Resistant Design Method for Steel Beams with Constraints given in the Code for Fire Protection of Building Steel Structures does not fully consider the influence of these parameters. The regression analysis of the results of the parametric analysis gives the applicable simplified method of calculating the fire resistance of confined steel beams considering creep.