钢筋水泥净浆同轴构件弯剪破坏过程的电磁特性初探

混凝土的损伤演化是其内部裂缝产生和扩展的过程，伴随损伤程度的发展，混凝土的电磁特性会产生相应变化。为探究钢筋混凝土构件损伤破坏过程中的力-电行为之间的关系和电磁波在其中的传播特性，借鉴同轴电缆结构，以中间和外部的钢筋为内、外导体，将介质相对较为均匀的水泥净浆作为电介质，设计了智能同轴钢筋水泥净浆构件（reinforced cement paste coaxial component，RCPCC）。根据电磁学的基本原理，对RCPCC构件进行了有限元分析，建立了反映RCPCC结构特点的损伤元件的等效电路简化模型及相应的电参数表达式，并据此分析了损伤程度对构件交流电路参数（串联阻抗值、串联电容和相角值）的影响。基于此，设计了RCPCC的弯剪破坏试验，利用LCR测量仪测量构件的交流电路参数随弯剪破坏过程的变化情况，同时用频谱分析仪记录了基波峰值在破坏时的变化情况。结果表明：RCPCC构件的弯剪破坏过程可划分为3个阶段，对应每个阶段的电磁特性参数变化速率不同，损伤演化的速率与所测得构件相关电参数变化速率一致；在破坏过程中力学和电学行为存在本征的必然联系，裂缝损伤发展会使串联阻抗值增大，串联电容和相角值减小；构件内部裂缝的发展会减小对电磁波传播的阻碍，引起基波峰值增大，基波峰值可表征构件的破坏程度。试验结果所呈现的规律与理论模型分析结果具有很好的一致性，验证了模型的可靠性。

Preliminary Investigation on Electromagnetic Characteristics of Reinforced Cement Paste Coaxial Member During Bending and Shear Failure

The damage evolution of concrete is a process during which internal cracks emerge and propagate, and correspondingly the electromagnetic properties of concrete is changed according to the degree of damage development. In order to figure out the relationship between mechanical properties and electric behaviors as well as the propagation properties of electromagnetic waves during the damaging or failure of reinforced concrete members, a reinforced cement paste coaxial component (reinforced cement paste coaxial component, RCPCC) was designed based on the principle of coaxial cable, in which cement paste was regarded as the dielectric for its homogeneousness. The inner bar and outer reinforcement cage were used as conductors. According to the basic principles of electromagnetism, the finite element analysis on RCPCC was carried out. Following that, the simplified equivalent circuit model of the components with different damage levels and the corresponding electrical parameter expressions that can characterize the structural properties of RCPCC were established. Based on this model, the effect of the damage degree on alternating current circuit parameters (series impedance value, series capacitance and phase angle value) of component was analyzed. Furthermore, the bending and shearing failure experiments on RCPCC were carried out. The alternating current circuit parameters of the component during the bending and shearing failure process were measured by LCR instrument. Meanwhile, the spectrum analyzer was used to record the variation of the fundamental peak during the testing. The results show that the bending and shearing failure process of RCPCC could be divided into three phases, and the change of electromagnetic property value of each phase was different. The changing rate of the measured electrical parameters was consistent with the damage evolution rate. Consequently, there was an intrinsic connection between mechanical properties and electrical behaviors during the failure process. With the propagation of cracks, series impedance value increased, while series capacitance and phase angle value decreased. With the internal crack development of the component, the obstruction of the electromagnetic wave propagation reduced, resulting in the increase of fundamental peak. The damage degree of the component could be characterized by fundamental peak. The laws conducted by the results of testing were in good agreement with the analysis results of theoretical model, which verified the reliability of the model.