高强钢约束柱受火后剩余承载性能实用评估方法

Practical Assessment Method for Postfire Residual Bearing Capacity of Restrained High Strength Steel Columns

摘要:

确定高强钢约束柱受火后剩余承载性能是高强钢结构受火后安全评估的关键。采用经验证的有限元模型对高强钢约束柱受火后剩余承载性能进行了系统的参数分析，考虑了最高过火温度、长细比、轴向约束刚度比、转动约束刚度比、荷载比、荷载偏心率以及高强钢强度等级与交货状态的影响。结果表明：当约束钢柱的最高过火温度小于最大轴向承载力温度时，受火升降温过程对剩余承载力的影响很小，此后剩余承载力随最高过火温度的增大而减小；在一定情况下，中长细比约束钢柱受火后剩余承载力的折减程度更严重，剩余承载力的折减程度随轴向约束刚度比、荷载比、荷载偏心率的增大而减小；转动约束刚度比通过影响钢柱的长细比而影响剩余承载力；QT 型 Q890 高强钢约束柱受火后剩余承载力的折减程度通常最小。结合参数分析结果与现行标准规定，提出了高强钢约束柱受火后剩余承载性能实用评估方法，包括高强钢约束柱受火后剩余承载力简化计算方法以及高强钢约束柱受火后可继续使用的条件与分级。

Abstract:

Determining the post-fire residual bearing capacity of restrained high strength steel columns is crucial for the post-fire safety assessment of high strength steel structures. A validated finite element model was used to conduct a systematic parametric analysis of the post-fire residual bearing capacity of restrained high strength steel columns, considering the effects of maximum fire temperature, slenderness ratio, axial restraint stiffness ratio, rotational restraint stiffness ratio, load ratio, load eccentricity, and high strength steel grade and manufacturing process. The results showed that when the maximum fire temperature of the restrained steel column was lower than the temperature corresponding to its maximum axial bearing capacity, the heating and cooling process during the fire had little effect on the residual bearing capacity. Beyond this point, the residual bearing capacity decreased as the maximum fire temperature increased. Under certain circumstances, restrained steel columns with medium slenderness ratios experienced more severe reductions in post-fire residual bearing capacity, and the degree of reduction decreased with an increase in the axial restraint stiffness ratio, load ratio, and load eccentricity. The rotational restraint stiffness ratio affected the residual bearing capacity by influencing the slenderness ratio of the steel column. The reduction degree of post-fire residual bearing capacity of the restrained QT Q890 high strength steel columns was usually the smallest. Based on the results of the parametric analysis and the provisions of current standards, a practical assessment method for the post-fire residual bearing capacity of restrained high strength steel columns was proposed. This method included a simplified calculation approach for determining the post-fire residual bearing capacity, along with conditions and classifications for the continued use of high strength steel columns after fire exposure.