Research On Acoustic Emission Characteristics Of Whole Failure Process Of Reinforced Concrete Simply Supported Beam

Acoustic emission test technology can preferably capture the internal damage signal of reinforced concrete structure,so that the key damage of the structure is early warning,therefore,the technology has a broad application prospect in the field of bridge detection.The midspan loading test of reinforced concrete beams is designed and carried out,and the acoustic emission characteristics of all beams during the whole failure process are studied.Based on the classical G-R formula,the b value of acoustic emission is deduced,calculated and improved,which is used for damage warning of reinforced concrete beam.The main work and achievements of the paper include:1.The experimental data of acoustic emission parameters in the flexural failure test of reinforced concrete beams are summarized and analyzed,and the typical characteristics of the main parameters of acoustic emission in different stages of beam damage are studied.The AE signals generated during beam loading are recorded in detail.2.Four pieces of reinforced concrete test beams have been designed and made,in which the stirrups of each beam are arranged differently at left and right half span.There are many kinds of damage forms such as bending cracking,bending shear cracking and abdominal shear cracking during loading.The AE signals generated during beam loading are recorded in detail.3.The acoustic emission characteristics of beam damage evolution process are studied by using parametric analysis method.The cumulative energy change curve during loading shows obvious "three inflection point" characteristics.The distribution range of the amplitude,frequency and duration of beam damage is determined.4.The attenuation coefficient of acoustic emission signal under surface breaking lead and loading condition is obtained through fitting.It is found that the attenuation of surface breaking lead signal is slower than that under loading.Using AEwin software,the attenuation of wave velocity is set up,and the location of AE source preliminarily studied.5.The classical G-R formula of seismology is applied to study the acoustic emission characteristics of concrete cracking damage.The a and b values of the acoustic emission at different loading stages of each beam are calculated.The b0 value obtained after the correction of the average value of the a value as the known quantity can be used as an important basis for the damage evolution of the beam body.When 1.4<b0<1.7,the bending crack in the bottom of the test beam appears;when 1<b0<1.2,the critical slanting crack appears;when b0<1,the fracture of the compression zone appears,and the beam is finally destroyed.