声发射监测锈蚀混凝土梁受弯的损伤与裂缝特征

Damage Characteristics and Crack Monitoring of Corroded Reinforced Concrete Beams in Bending Process Based on Acoustic Emission Techniques

钢筋锈蚀一直是钢筋混凝土结构退化的主要原因之一,识别锈蚀混凝土结构内部损伤信号,将为既有建筑物的结构健康监测提供理论依据。采用声发射(AE)技术在微观裂缝水平上研究钢筋锈蚀对钢筋混凝土(RC)梁弯曲特性的影响。声发射信号的上升时间/峰值幅值(R/A)、振铃计数/持续时间(AF)和改进后的b值分析将用以反映钢锈蚀作用下钢筋混凝土试件裂纹模式和破坏模式的变化。结果表明,随着钢筋锈蚀率的增加,锈蚀钢筋混凝土梁的极限承载力显著降低;声发射信号与混凝土损伤之间有很好的对应关系,试件的损伤过程可以分为3个损伤阶段:初始损伤阶段,损伤演化阶段、持续损伤增长阶段。b值曲线的变化趋势可以反映裂缝的形成和发展。随着荷载的增加,试件的剪切裂缝比例逐渐上升,且在持续损伤阶段,试件锈蚀程度越高,剪切裂缝比例越高。

Reinforcement corrosion has been one of the major causes of degradation of reinforced concrete structures.Identifying the internal damage signals of corroded RC structures will provide a theoretical basis for structural health monitoring of existing buildings.This study investigated the effect of steel corrosion on the flexural characteristics of RC beams at the microscopic crack level using acoustic emission(AE)technique.The rise time/peak amplitude(R/A),ringing count/duration(AF)and improved b(Ib)values of the acoustic emission signal were calculated for reflecting the changes in cracking patterns and damage modes of corroded RC beams.The results show that the ultimate load capacity of rusted reinforced concrete beams decreases significantly with the increase of reinforcement corrosion rate.there is a good correspondence between acoustic emission signal and concrete damage,and the damage process of the specimen can be divided into three damage stages:initial damage stage,damage evolution stage,and sustained damage growth stage.Besides,the trend of b-value curve can reflect the formation and development of cracks.Moreover,with the increase of load,the proportion of shear cracks in the specimen gradually increases,and the higher the degree of corrosion of the specimen in the sustained damage stage,the higher the proportion of shear cracks.