钢筋混凝土结构抗火性能研究进展

State of the art on fire resistance of reinforced concrete structure

摘要:

随着建筑火灾的频繁发生，钢筋混凝土结构发生火灾的情况也日益增多。在火灾中建筑材料的力学性能降低将导致钢筋混凝土结构发生破坏甚至倒塌。前期人们对钢筋混凝土梁、柱和节点的抗火性能进行了试验研究。由于试验条件不同，其耐火极限计算公式在不同试验条件下的计算精度较低。因此，文章综述了钢筋混凝土梁、柱、节点和框架抗火性能等方面的研究并进行了梳理，考虑了混凝土保护层厚度、荷载比和配筋率等试验参数对耐火极限的影响，回顾了杆系模型、Rankine方法和刚度法等理论分析方法的研究进展，还总结了有限元分析和耐火极限计算公式的研究进展。结果表明：钢筋混凝土梁的耐火极限受荷载比、混凝土保护层厚度和配筋率等参数的影响较大，钢筋混凝土柱的耐火极限受荷载比和荷载偏心率等参数的影响较大，钢筋混凝土节点的耐火极限则取决于节点周边钢筋混凝土梁、柱的耐火极限。此外，还收集了129篇文献的试验数据并归纳了荷载比、混凝土保护层厚度和配筋率等试验参数对耐火极限的影响规律，对不同条件的试验结果进行了统一化规制并对其耐火极限进行了参数相关性分析，选取了相关性大于0.1的参数作为影响耐火极限的重要参数。通过机器学习和非线性回归分析方法，提出了钢筋混凝土梁和柱的耐火极限计算公式，其 分别为0.935和0.895，计算结果与实验结果吻合较好，表现出较高的准确性，为钢筋混凝土结构的抗火设计提供可靠参考。

Abstract:

The occurrence of fires in reinforced concrete (RC) structures increases with the growing occurrence of building fires. The mechanical properties of building materials are greatly reduced in fire, which leads to the failure or even collapse of RC structures. Extensive experimental studies have been conducted in the early stages to investigate the fire resistance of RC beams, columns and joints. Due to the different experimental conditions, the accuracy of the fire resistance calculation formula is relatively low in other conditions. Therefore, the state of the art of RC beams, columns, joints and frames was summarized in this paper. Among them, parameters such as concrete cover thickness, load ratio and reinforcement ratio were considered. The theoretical analysis such as strut-and-tie-model, Rankine method and nominal stiffness method was summarized, and the finite element analysis and fire resistance calculation formulas were also summarized. The results indicated that the fire resistance of RC beams was greatly affected by parameters such as load ratio, concrete cover thickness and reinforcement ratio. The fire resistance of RC columns was greatly affected by parameters such as load ratio and load eccentricity. The fire resistance of RC joints depends on the fire resistance of RC beams and columns near the joint. Furthermore, a large amount of test data on RC beams and columns was collected from 129 references, and the influencing rules of parameters such as load ratio, concrete cover thickness and reinforcement ratio were summarized. The test data under different conditions were standardized, and the parameter analysis was conducted on the test data. The parameters with a correlation degree greater than 0.1 were identified as important parameters. The fire resistance calculation formulas of RC beams and columns were proposed by the machine learning and regression analysis. The results indicate that the proposed formulas with of 0.935 and 0.895 exhibit high accuracy, and the calculated values are highly consistent with the test values. The proposed formulas can be regarded as a reliable reference for the fire resistance design of RC structures.