基于声发射的单侧向受压竖向受循环加卸载的混凝土损伤特性研究  

Damage Characteristics Research of Concrete Based on the Acoustic Emission Bidirectional Compression Vertical Cyclic Loading and Unloading Conditions

作　　者：马小亮[1] 彭刚[1] 王孝政[1] 肖杰[1] 

机构地区：[1]三峡大学土木与建筑学院,443002

出　　处：《灾害与防治工程》2015年第2期16-24,共9页Disaster and Control Engineering

摘　　要：在水平单向侧压应力作用下，进行了竖向等应变步长循环加卸载的混凝土抗压性能试验。对不同侧应力状态下的外包络线、共同点轨迹线和循环加卸载全曲线进行了分析，研究了侧应力对累积残余塑性应变和刚度退化的影响，建立了不同侧应力状态下的应力、应变时间曲线与声发射参数之间存在的关系；在此基础上，探索了混凝土在加载全过程中的能量释放特性，基于声发射事件数构建的损伤变量分析了混凝土的损伤规律。研究结果表明：在单个循环加卸载过程中，声发射事件数主要发生在加载阶段，卸载阶段出现较少，卸载段的声发射能量随侧向压应力的增加而增加；在整个循环加卸载试验过程中，声发射事件数主要集中在峰值应力以前，峰值应力以后出现较少，峰值应力后的声发射能量随侧向压应力的增大而增大；混凝土刚度退化速度及累积残余塑性应变随侧压应力的增加而减小；损伤变量随累积残余塑性应变的增加而增大，其速度呈先增加后减小的规律，损伤演化过程可大致分为损伤起始、损伤线性增长、损伤失稳3个阶段；不同侧向压应力下混凝土损伤发展路径各异，但损伤发展的起点和终点是固定的，侧压应力越高，损伤路径越短，水平与竖向荷载间的大小比例，决定了混凝土损伤的主导因素与损伤机制。Experimental study on the compressive properties of concrete were carried out under the conditions of uniaxial lateral stress and vertically equal strain cyclic loading and unloading. The cyclic loading and unloading curves, outsourcing curves and common-point track were analysed under different lateral stress conditions. The influences of lateral stress on stiffness degradation and cumulative residual plastic strain were studied. The cor- responding relationships between stress-time, strain-time curve and synchronously acoustic emission parameters were established under different lateral stresses. On the basis of those, energy release characteristics were explored in the whole loading process of the con- crete. The damage characteristics of concrete were analyzed through the damage variable that determined by the number of acoustic emission energy. The results show that the number of acoustic emission energy mainly focused on the loading phase in a single cycle of loading and unloading process, but it emerged less in the unloading phase. AE energy in- creased with laterally compressive stress adition on unloading phase. Throughout the course of cyclic loading tests, the number of acoustic emission energy concentered on previ- ous peak stress, there is less after the peak stress. And the acoustic emission energy in- creased with the increase of lateral stress after peak stress. With the increase of the lateral- ly compressive stress, concrete stiffness degradation rate and accumulated residual plastic strain decreased. The value of damage variable increased gradually, the rate of the increase showed a trend from increase to decrease, and damage evolution process can be roughly di- vided into the three stages that initial damage stage, linear growth stage, damage unstable stage. The material damage development path was different under different lateral stres- ses, but the start and end point of damage meet with each other. What＇s more, the higher the lateral stress, the shorter the damage path, the size r

关 键 词：混凝土 循环荷载 损伤特性 刚度退化 声发射 

分 类 号：TU528.01[建筑科学—建筑技术科学]