Fire Resistance Analysis of RC Beam Supporting Column Transfer Structure Joints
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摘要: 为提供钢筋混凝土梁托柱转换结构的防火设计依据，根据结构的受力特点，设计了两种足尺梁托柱节点单元试件，对两种节点单元试件进行了热力耦合作用下的耐火性能试验；采用有限元分析软件进行数值计算，分析了火灾下钢筋混凝土梁托柱节点单元的热力耦合耐火极限，得出各参数变化对梁托柱节点单元耐火极限变化规律. 分析结果表明：升温曲线及最高温度对节点单元的耐火极限影响较大；荷载比为0.6的节点单元比荷载比为0.4节点单元耐火极限小；节点单元托梁纵向受拉钢筋的保护层厚度不同，其耐火极限从大到小为保护层厚度50 mm、保护层厚度40 mm、保护层厚度25 mm；转换托梁中受托柱处附加吊筋的设置可有效提高节点单元的耐火极限，并起到避免发生突然破坏的作用；节点单元托梁四面受火的耐火极限小于三面受火的耐火极限；在相同荷载比及相同受火工况作用下，两种钢筋混凝土梁托柱节点单元的耐火极限和破坏特点不同.Abstract: To provide the basis for the fire prevention design of reinforced concrete beam supporting column transfer structures, according to the structural characteristics, two kinds of full size beam supporting column transfer structure joints are designed. The reinforced concrete beam supporting column transfer structure joints are exposed to fire, and their fire resistance is tested. Based on the test results, using ABAQUS —a finite element analysis software, considering the influence of raising temperature curve, loading ratio, protective layer thickness, additional steel bars, the number of surfaces in fire of a transfer girder, the fire resistance of beam supporting column transfer structure joints is analyzed and the variation of the fire resistance for these beam supporting column transfer structure joints is summarized. The analysis results show that heating curve and maximum temperature have a significant influence on fire resistance; the fire resistance limit of joint units with load ratio of 0.6 is smaller than that of joint units with load ratio of 0.4; the thickness of the protective layer of the longitudinal tensile reinforcement of the joint unit differs, while the fire resistance limit ranges from large to small for protective layer thickness of 50 mm, 40 mm, and 25 mm, respectively; hanging steel bars in the transfer girder can improve the fire resistance and help avoid sudden damage. The more surfaces of the transfer girder are in fire, the shorter is the fire resistance. Under the same loading ratio, two kinds of beam supporting column transfer structure joints have different damage characteristics and fire resistance.
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图 1 节点单元示意图及内力简图
Figure 1. The schematic diagram of beam supporting column joint unit model
图 7 转换托梁钢筋保护层厚度对耐火极限的影响
Figure 7. Influence of thickness of the concrete protecting layer on the fire resistance
图 8 梁托柱节点附加钢筋对耐火极限的影响
Figure 8. Influence of additional reinforcement on the fire resistance
表 1 实测钢筋强度指标
Table 1. Measured strength of reinforcement
钢筋直径/mm 屈服强度/MPa 抗拉强度/MPa 屈服强度
/抗拉强度8 380.0 490 0.78 12 545.0 655 0.83 16 545.0 690 0.79 18 412.5 500 0.83 20 430.0 575 0.75 
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表 2 试件荷载及受火工况设计
Table 2. Parameter design
编号 名称 转换托梁
受火数/面受托柱顶端施
加恒载/kN转换托梁
荷载比1 TZHA3-1 3 48.2 0.4 2 TZHA3-2 3 72.3 0.6 3 TZHA4-1 4 48.2 0.4 4 TZHA4-2 4 72.3 0.6 5 TZHB3-1 3 34.4 0.4 6 TZHB3-2 3 51.6 0.6 7 TZHB4-1 4 34.4 0.4 8 TZHB4-2 4 51.6 0.6
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表 3 梁托柱节点单元模型参数设置
Table 3. Parameter design
编号 名称 升温曲线 转换托梁
受火数/面受托柱顶端
施加恒载/kN转换托梁
荷载比转换托梁保护
层厚度/mm吊筋直径
/mm节点处箍筋
间距/mm1 TZHA3 ISO834 3 48.2 0.4 25 12 100 2 TZHA3-shice1 实测1 3 48.2 0.4 25 12 100 3 TZHA3-shice2 实测2 3 48.2 0.4 25 12 100 4 TZHA3-DJ-0 ISO834 3 48.2 0.4 25 0 100 5 TZHA3-DJ-6 ISO834 3 48.2 0.4 25 6 100 6 TZHA3-DJ-8 ISO834 3 48.2 0.4 25 8 100 7 TZHA3-DJ-16 ISO834 3 48.2 0.4 25 16 100 8 TZHA3-DJ-18 ISO834 3 48.2 0.4 25 18 100 9 TZHA3-GJ-50 ISO834 3 48.2 0.4 25 12 50 10 TZHA3-GJ-150 ISO834 3 48.2 0.4 25 12 150 11 TZHA3-bh40 ISO834 3 42.7 0.4 40 12 100 12 TZHA3-bh50 ISO834 3 39.1 0.4 50 12 100 13 TZHA4 ISO834 4 48.2 0.4 25 12 100 14 TZHB3 ISO834 3 34.4 0.4 25 12 100 15 TZHB3-DJ-0 ISO834 3 34.4 0.4 25 0 100 16 TZHB3-DJ-6 ISO834 3 34.4 0.4 25 6 100 17 TZHB3-DJ-8 ISO834 3 34.4 0.4 25 8 100 18 TZHB3-DJ-16 ISO834 3 34.4 0.4 25 16 100 19 TZHB3-DJ-18 ISO834 3 34.4 0.4 25 18 100 20 TZHB3-GJ-50 ISO834 3 34.4 0.4 25 12 50 21 TZHB3-GJ-150 ISO834 3 34.4 0.4 25 12 150 22 TZHB4 ISO834 4 34.4 0.4 25 12 100
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