| 考虑防火涂料的PC箱梁时空温度场及刚度退化试验研究 |
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| 引用本文： | 侯炜,张岗,李源,胡文亮.考虑防火涂料的PC箱梁时空温度场及刚度退化试验研究[J].中国公路学报,2021,34(6):57-68. |
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| 作者姓名： | 侯炜 张岗 李源 胡文亮 |
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| 作者单位： | 1. 长安大学 旧桥检测与加固技术交通运输行业重点实验室, 陕西 西安 710064;2. 长安大学 公路学院, 陕西 西安 710064 |
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| 基金项目： | 国家自然科学基金项目（51878057）；陕西省自然科学基础研究计划项目（2021JM-174）；中央高校基本科研业务费专项资金项目（300102210105） |
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| 摘 要： | 为了明确涂有防火涂料的预应力混凝土（PC）箱梁火灾温度场及火灾后的刚度退化性能，针对3片有、无膨胀型防火涂料的PC简支箱梁开展了火灾模型试验研究。基于预应力混凝土梁受火性状推导了刚度衰变率与挠度衰变率关系方程，通过分析混凝土箱梁截面时空温度场分布状态，基于分区域理论提出了一种PC箱梁受火损伤后初始截面等效刚度简化计算方法，并基于自振频率推导了受火梁动刚度计算公式；对模型梁进行了火灾后的静力逐级加载和动力性能试验，分析了受火梁挠度、频率等静、动力参数的变化规律，研究了受火损伤状态对箱梁静、动力特征参数的影响；基于理论计算和试验数据对比分析了受火梁静、动力刚度在不同损伤状态下的退化规律。研究结果表明：膨胀型防火涂料的使用显著降低了预应力混凝土箱梁的高温敏感性，混凝土温升速率明显下降，大幅降低了混凝土结构温度，有效减少了混凝土结构开裂和爆裂现象；受火试验梁的截面静刚度随荷载增加而逐渐减小，且初始损伤越大，进入弹塑性阶段发展越快，越早达到结构极限承载力；初始损伤状态对结构截面静刚度的影响大于对结构动刚度的影响，且截面静刚度衰减速率比动刚度衰减速率更快。提出的受火梁静、动刚度及固有频率的简化计算方法可为火损箱梁的结构静、动力性能初评估提供理论依据。
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| 关 键 词： | 桥梁工程 预应力混凝土箱梁 火灾试验 温度场 静动刚度 挠度 频率 |
| 收稿时间： | 2020-09-15 |
Experimental Study on Temperature Field and Stiffness Degradation of PC Box Girder Considering Fire-retardant Coating |
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| HOU Wei,ZHANG Gang,LI Yuan,HU Wen-liang.Experimental Study on Temperature Field and Stiffness Degradation of PC Box Girder Considering Fire-retardant Coating[J].China Journal of Highway and Transport,2021,34(6):57-68. |
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| Authors: | HOU Wei ZHANG Gang LI Yuan HU Wen-liang |
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| Affiliation: | 1. Key Laboratory of Transport Industry of Bridge Detection Reinforcement Technology, Chang'an University, Xi'an 710064, Shaanxi, China;2. School of Highway, Chang'an University, Xi'an 710064, Shaanxi, China |
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| Abstract: | To study the temperature field and stiffness degradation performance of prestressed concrete (PC) simply supported box girder with fire retardant coating, a fire model test was carried out for three PC simply supported box girder with and without fire retardant coating. Firstly, based on the fire behavior of prestressed concrete beams, the relationship between stiffness decay rate and deflection decay rate was derived; Secondly, a simplified estimation method of equivalent stiffness of PC box girder section after fire damage was proposed based on the partition theory, and the calculation formula of the dynamic stiffness of the beam under fire was derived based on the natural frequency. Then, the static step-by-step loading and dynamic performance tests of the model beam after fire were carried out, and the variation rules of static and dynamic parameters such as deflection and frequency of the beam under fire were analyzed, and the influence of the fire damage state on the static and dynamic characteristic parameters of the box girder was studied; Finally, based on the theoretical calculation and test data, the degradation rule of static and dynamic stiffness of the beam under different damage conditions was analyzed. The results show that the application of intumescent fire retardant coating can significantly reduce the high temperature sensitivity of prestressed concrete box girder, the temperature rise rate of concrete decreases significantly, the temperature of concrete structure is greatly reduced, and the cracking and bursting phenomenon of concrete structure is effectively reduced. The greater the initial damage, the faster the development of the elastic-plastic stage, and the earlier the ultimate bearing capacity of the structure is reached. The influence of the initial damage state on the static stiffness of the structure is greater than that on the dynamic stiffness of the structure, and the attenuation rate of the static stiffness of the section is faster than that of the dynamic stiffness. The natural frequency calculation method and dynamic stiffness calculation formula proposed in this paper can be used to evaluate the dynamic performance of damaged box girder. |
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| Keywords: | bridge engineering PC box girder fire test temperature filed static and dynamic stiffness deflection frequency |
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