极端火灾作用下超高层钢管混凝土结构的损伤演化与修复技术

Damage Evolution and Repair Technologies of Super High-Rise Concrete-Filled Steel Tubular (CFST) Structures under Extreme Fire

摘要: 为揭示极端火灾(升温速率>20℃/min、峰值温度>1200℃)对超高层钢管混凝土结构的损伤机理，提出针对性修复技术，本文通过试验研究与数值模拟相结合的方法开展系统研究。设计3组不同参数的钢管混凝土试件(φ300 × 8 mm钢管、C60/C80混凝土)，采用ISO 834标准升温曲线叠加极端火灾修正系数进行高温试验，测试温度场分布、力学性能退化及损伤特征；基于ABAQUS建立热–力耦合数值模型，验证试验结果的同时分析超高层结构整体损伤演化规律；最后提出“损伤评估–局部修复–整体加固”的三级修复方案，并通过足尺模型试验验证修复效果。研究表明：极端火灾下钢管混凝土结构损伤呈现“温度梯度主导–界面剥离加剧–承载力突变下降”的特征，C80混凝土试件在1000℃时承载力损失达72.3%；采用“碳纤维布加固 + 聚合物修补砂浆”复合修复技术后，结构承载力恢复率可达89.7%，满足规范安全要求。本文成果可为超高层钢管混凝土结构的抗火设计与灾后修复提供理论支撑和工程参考。

Abstract: To reveal the damage mechanism of super high-rise concrete-filled steel tubular (CFST) structures under extreme fire (heating rate > 20˚C/min, peak temperature > 1200˚C) and propose targeted repair technologies, this study conducts a systematic investigation through a combination of experimental research and numerical simulation. Three groups of CFST specimens with different parameters (φ300×8mm steel tubes, C60/C80 concrete) were designed. High-temperature tests were carried out using the ISO 834 standard temperature-time curve superimposed with an extreme fire correction coefficient to measure the temperature field distribution, mechanical property degradation, and damage characteristics. A therm-mechanical coupled numerical model was established based on ABAQUS to verify the experimental results and analyze the overall damage evolution law of super high-rise structures. Finally, a three-level repair scheme of “damage assessment - local repair - overall strengthening” is proposed, and the repair effect is verified through full-scale model tests. The results show that the damage of CFST structures under extreme fire exhibits the characteristics of “temperature gradient dominance - aggravated interface debonding abrupt drop in bearing capacity”. The bearing capacity loss of C80 concrete specimens reaches 72.3% at 1000˚C. After adopting the composite repair technology of “carbon fiber reinforced polymer (CFRP) sheet strengthening + polymer repair mortar”, the structural bearing capacity recovery rate can reach 89.7%, which meets the code safety requirements. The results of this study can provide theoretical support and engineering reference for the fire-resistant design and post-fire repair of super high-rise CFST structures.