宋方远 谢旭 张婷婷

摘 要：锈蚀是钢桥耐久性退化的主要形式之一，而锈蚀钢材的表面形貌是改变结构应变分布进而影响超低周疲劳性能的重要因素。为了研究钢材锈蚀形貌及其对超低周疲劳性能的影响，以中国钢桥建设中常用的Q345钢材为例，对4组不同锈蚀程度的人工加速锈蚀钢板试样进行表面形貌测量，讨论了用粗糙度、分形维数和功率谱密度函数3种指标表征锈蚀形貌的可能性;根据三维形貌实测数据建立试样的规整六面体单元模型，并利用循环空穴扩张模型（CVGM）计算了锈蚀钢材的超低周疲劳开裂寿命，分析了锈蚀形貌对钢材超低周疲劳开裂寿命的影响。结果表明：人工加速锈蚀试验的锈蚀速率受锈层阻隔影响明显;对于不同锈蚀时长的试样，各组表面轮廓的粗糙度、分形维数和功率谱密度函数区分度不高;锈蚀形貌的不均匀程度是引起试样超低周疲劳性能下降的重要因素，蚀坑位置的超低周疲劳开裂寿命受蚀坑所处截面缩小程度、所处位置以及形状特征等不均匀因素耦合影响。

关键词：钢桥抗震;蚀坑;钢材锈蚀;超低周疲劳;有限元建模

Abstract： Corrosion is one of the most typical form of durability degradation of steel bridge and the corrosion morphology takes significant effect on the strain distribution of the structural surface，which has evident effect on the ultra-low cycle fatigue performance of steel plate. In order to investigate the characteristics of steel corrosion morphology as well as the effect of the corrosion on the structural ultra-low cycle fatigue（ULCF） performance， this paper takes the steel kind of Q345 as the study case， conducting surface morphology measurements of four groups of artificially accelerated corroded steel plate sampleswith different corrosion degrees.The possibility of characterizing the corrosion morphology by roughness， fractal dimension and power spectral density function is discussed.Meanwhile， precise finite element models consistedby hexahedron elements of corroded specimens are established on the basis of 3D profile data， the ULCF cracking life of corroded steel is calculated using the improved cyclic void growth model （CVGM），and the effect of corroded surface morphology on ULCF cracking life of steel is analyzed.The research results indicate that： the corrosion rates of the artificial acceleration corrosion tests are significantly affected by the thickness of the rust layers.However， the surface roughness， fractal dimension， and power spectrum density function are unable to differentiate the corrosion degree.According to the numerical calculation results， the unevenness of corrosion morphology is the very important factor on the UCLF performance degradation.Also， the reduction of the cross section， the position on the surface of specimens， and the dimension characters of the critical corruption pits contribute a coupling effect on the ULCF cracking life of the corroded steel specimens.

Keywords： seismic design of steel bridge; corrosion pit; steel corrosion; ultra-low cycle fatigue （ULCF）; finite element modeling

在1994年美國北岭地震[1]和1995年日本阪神地震[2]中，不少钢结构在梁柱节点或桥墩底板连接位置发生了超低周疲劳破坏。与破坏性质为脆性断裂或伪脆性的高周疲劳和低周疲劳不同，超低周疲劳的破坏机理是钢材局部塑性大应变引起材料延性开裂，破坏性质为延性断裂，疲劳寿命一般在20周以内[3]。……