局部腐蚀圆钢管混凝土性能与评估

Concrete-filled steel tubes (CFSTs) possess high load-carrying capacity, good ductility, excellent energy dissipation ability and so on, hence they are widely used in structures. However, the corrosion of steel tubes appears during service stage. The corrosion of CFSTs commonly appears as local corrosion of steel tube, which would result in deterioration of steel properties, decrease of tube thickness, concentration of stress, local buckling of steel tube and early failure of steel tube. Thus the confinement effect on core concrete decreases obviously, which results in potential safety hazard during service stage. Therefore, it is necessary to study the behavior of CFSTs with local corrosion. In this project, combining with theoretical and experimental research method, the static and hysteretic behavior of circular CFSTs with local corrosion will be studied. The neutral salt spray accelerated corrosion method will be applied to model the corrosion of steel tube. The concentration of stress, fracture behavior, local buckling of corroded tube will be considered in analysis. The interaction behavior between corroded steel tube and core concrete will be analyzed in detail. The deterioration of load-carrying capacity and seismic capacity will be studied. Also, the calculation method of load-carrying capacity considering local corrosion of circular CFSTs will be proposed. The assessment method to evaluate the earthquake resistance of circular CFSTs with local corrosion will be suggested. The research work will contribute to the safety assessment and retrofit of corroded CFSTs.

钢管混凝土具有承载力高、延性好、耗能能力强等优点，因此在工程中得到广泛应用。但钢管混凝土服役期间钢管易生锈腐蚀，且以局部腐蚀为主，严重的局部腐蚀会劣化钢材材性、减薄管壁、产生应力集中，致使钢管出现局部屈曲或过早破坏，从而显著降低钢管对核心混凝土的约束效果，降低构件承载力、延性和耗能能力，导致结构存在安全隐患，因此有必要研究局部腐蚀钢管混凝土受力性能。本项目采用理论分析与试验研究相结合的方法进行局部腐蚀圆钢管混凝土静力与抗震性能研究，采用中性盐雾加速腐蚀试验方法进行钢管局部腐蚀，分析中考虑腐蚀处钢管应力集中与断裂破坏过程，研究局部腐蚀缺陷和局部屈曲耦合作用下钢管混凝土受力性能，研究腐蚀圆钢管与核心混凝土相互作用机理，进行构件腐蚀后承载力和抗震性能退化研究，提出考虑局部腐蚀圆钢管混凝土承载力和抗震性能评估方法，为在役腐蚀钢管混凝土的安全评估与维修加固提供决策。

本项目采用试验研究、有限元模拟及理论分析相结合的方法，分别从材性和构件层面系统研究了局部腐蚀对圆钢管混凝土受力性能的影响。在材性层面，基于盐雾腐蚀试验、腐蚀后表面三维形貌和单调拉伸试验，研究了钢板的腐蚀特征及其腐蚀后的材性退化机理。在构件层面，首先进行了局部腐蚀后构件静力性能研究。针对模拟局部腐蚀轴压短柱试验与有限元参数分析，在此基础上进行了模拟局部腐蚀圆钢管混凝土长柱轴压和偏压试验研究和有限元分析。基于试验研究和理论分析结果，提出了局部腐蚀后圆钢管混凝土轴压短柱截面承载力、轴压长柱稳定承载力和压弯构件承载力的计算方法。最后对局部腐蚀后圆钢管混凝土的滞回性能进行了试验研究和有限元分析。研究结果表明，局部腐蚀会造成钢板承载力降低，并会引起应力集中效应从而导致变形能力降低；圆钢管混凝土上的局部腐蚀不仅会使构件截面积减小，还会使外钢管对核心混凝土的约束效果减小甚至丧失，圆钢管混凝土截面承载力、延性和刚度降低，局部腐蚀的轴向尺寸对构件承载力和延性的影响大于环向尺寸的影响；局部腐蚀的存在会使圆钢管混凝土的滞回性能出现劣化，承载力、耗能能力和延性随着局部腐蚀区域的增大而降低。本项目的研究结果可为在役腐蚀钢管混凝土的安全评估提供依据。