装配式钢结构模块连接节点耐火性能试验研究

摘 要：以“角件旋转式连接模块”钢结构节点作为研究对象，开展了两种不同防火保护条件下节点的耐火性能试验，研究不同防火保护条件下节点的变形特点、破坏形态和耐火性能，试验方法遵循国家标准GB/T 9978.1-2008。试验表明：1）钢柱采用三层高性能防火石膏板（15+20+20） mm进行保护、钢梁采用双层高性能防火石膏板（20+20） mm进行包覆的节点试件A，在试验试件193 min内未发生破坏，除节点中间部位部分防火板发生脱落外，试件保护层整体保持较好的完整性，钢柱截面角部的温度测点受两个面的传热作用升温速度较快；由于节点角件的壁厚较厚，其温度整体略低于钢柱与钢梁；钢梁由于截面形状系数较大且防火保护弱于钢柱，钢梁温度较高；从试件的轴向变形曲线中可以看出整个试验过程中试件基本处于受热膨胀状态，未达到耐火极限。2）钢柱、钢梁均用60 mm厚的岩棉（120 kg/m3）及2层12 mm厚纤维增强型硅酸钙板进行包覆的节点试件B，试验过程中随着温度升高试件发生膨胀，防火板之间的拼缝不断扩大，但防火保护层基本保持相对完好的状态；131 min时试件开始出现压缩变形，为保障试验炉的安全停止试验；试件B各测点的温度分布规律总体上与试件A类似，但各测点升温曲线存在较大的离散性，这可能与该试件的轻钢龙骨变形造成防火板间拼缝扩大有关，炉内热烟气从拼缝进入试件内部，导致各测点的升温存在较大差异；从柱的轴向变形曲线可以看出在约128 min时钢柱已经停止膨胀并出现压缩趋势，表明试件已经开始出现局部或整体屈曲，试件开始进入破坏阶段，根据相关试验经验试件将较快达到耐火极限；试验结束后，可观察到钢柱局部已经发生轻微屈曲；综合判断，该试件基本接近失效状态。3）两个试件的温度曲线在100 ℃左右均持续了一定时间形成曲线平台，这主要是由于防火保护材料中的水分蒸发带走热量，延缓了温度的升高；4）试件B防火保护层板材的完整性相对较好，但是由于轻钢龙骨受热变形导致拼缝出现了较大的开裂，使钢结构的升温更高，因此采用轻钢龙骨进行固定的防火保护方式应选用稳定性较好的轻钢龙骨并安装牢固。5）试验得出装配式钢结构试验试件在三层高性能防火石膏板（15+20+20） mm的保护下，连接节点的耐火极限不低于3.00 h；在双层12 mm厚纤维增强型硅酸板和60 mm厚岩棉的保护下，连接节点的耐火极限不低于2.00 h。

Experimental study on fire resistance of connections in prefabricated modular steel structures

Abstract: This paper focuses on steel connections using “rotating angle connecting module” in prefabricated modular structures. Fire resistance tests were carried out to study the fire performance of the steel connections with two different fire protection methods. The deformation curves, failure modes and fire resistance of the connections were studied. The National Standard GB/T 9978.1-2008 was applied to carry out the tests. Test results show: 1) for specimen A of which the columns were protected with 3-layers of high-performance gypsum boards (15+20+20) mm and the beams were protected with 2-layers of high-performance gypsum boards (20+20)mm, the fire resistance rating was more than 193 min. The gypsum boards remained a relatively good integrity, but a few gypsum boards in the middle of specimen fell off. The temperature at the steel column corners were higher due to the 2-diretional heat transfer. The temperature of connection was lower than that of steel columns and beams, due to the fact that the connection has thicker steel than columns and beams. The temperature of beams were higher than that of columns because beams had larger section factor. From the axil displacement of columns it could be sawn that the specimen stayed in its thermal expansion stage and the criteria of fire resistance rating were not met yet. 2) for specimen B of which the columns and beams were protected with 2-layers of fiber-reinforced calcium silicate boards and 60 mm-thick rock wool（120 kg/m3）, the specimen was elongated as the steel temperature raised up, and the gaps between gypsum boards expanded, but the boards remained integrity; the specimen started to reveal compression deformation at 131 min, and the test was stopped to prevent any damage to the furnace. It was shown that specimen B has similar temperature profiles as specimen A, but there was divergence among the temperature profiles because deformed steel stud at high temperature caused large gaps between gypsum board, and hot gases might reach the specimen through gaps and result in deferent temperature profiles at different spots. From the axil displacement of columns it could be sawn that the column stopped thermal expansion and stared to crush. Therefore, the specimen started to buckle, and it reached its failure stage and would fail soon. After the test, local buckling was observed on the column. Based on the results, specimen B was very closed to its failure at the end of the test. 3) the temperature curves showed a plateau at about 100 ℃ for both specimens, and this is because the moisture in the specimens evaporated and absorbed a large amount of heat. 4) for specimen B, the gypsum boards remained integrity, but the gaps between gypsum boards expanded a lot due to the deformation of steel studs at high temperature. Therefore, the stability of steel studs at high temperature is very important if they are used for supporting gypsum boards. 5) Test results show that the connection protected with 3-layers of high-performance gypsum boards (with thickness of (15+20+20) mm) has a fire-resistance rating of 3.00 h, while the connection protected with 2-layers of fiber-reinforced calcium silicate boards and 60 mm-thick rock wool has a fire-resistance rating of 2.00 h.