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作 者:苏铭 顾爱军[1] 王举国 SU Ming;GU Aijun;WANG Juguo(College of Hydraulic Science and Engineering,Yangzhou University,Yangzhou 220059)
机构地区:[1]扬州大学水利科学与工程学院,江苏扬州225009
出 处:《扬州大学学报(自然科学版)》2021年第3期55-62,68,共9页Journal of Yangzhou University:Natural Science Edition
基 金:国家自然科学基金资助项目(52079120);国家自然科学基金青年科学基金资助项目(51809227).
摘 要:利用声发射技术分别对钢筋混凝土梁四点弯曲分级加载和素混凝土梁四点弯曲连续加载过程进行了监测,旨在探寻试验过程中声发射幅值、能量、振铃计数及声发射b_(a)值的变化规律,为预测混凝土梁的损伤破坏提供依据.试验结果表明:相比于b值,b_(a)值更能反映两种梁内部裂纹的萌发、扩展情况;当梁即将发生严重损伤时,相应的b_(a)值连续下降,并在损伤时刻达到极小值;在钢筋混凝土梁分级加载的三个阶段中,b_(a)值在Kaiser效应和载荷保持阶段上升,而在有效加载阶段呈下降趋势;素混凝土梁连续加载条件下,b_(a)值的变化可分为四个阶段:前期平稳、中期波动、后期下降、破坏后再次上升,即无论何种加载方式,结构在出现较大程度损伤或断裂失稳前,b_(a)值均呈现连续下降趋势.因此,b_(a)值连续下降的趋势可作为判断混凝土梁损伤、破坏的前兆,为预测实际工程发生的损伤提供判断依据.Acoustic emission(AE)signals in the process of reinforced concrete beams under four-point bending progressive loading and plain concrete beams under four-point bending continuous loading are collected.By studying the change rules of amplitude,energy,ringing count of AE and the b_(a)-value of AE,a basis can be provided for predicting the failure and damage of concrete beams.The results show that compared to b-value,b_(a)-value can obviously reflect the generation and propagation of cracks in the beams.When the beam is about to be seriously damaged,the corresponding b_(a)value decreases continuously and reaches the minimum value at the moment of damage.Under the condition of progressive loading of reinforced concrete beams,each stage of loading can be divided into three stages.The b_(a)-value rises in Kaiser effect stage and loading unchanged stage,and drops in effective loading stage.Under the condition of continuous loading of plain concrete beams,the changes of b_(a)-value can be divided into four stages:stable in the early stage,fluctuating in the middle stage,decline in the later period,rise again after failure.No matter what kind of the loading method,b_(a)-value presents a continuous downward trend before the structural damage or fracture occurs.So the continuous decline of b_(a)-value can be used as a precursor to judge the damage and failure of concrete beams,and it provides the judgment basis for predicting the damage of actual projects.
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