Research On Concrete Finite Element Model Revision Method Based On Acoustic Emission Parameters

With the extensive application of modern concrete structures,the endless structural safety accidents make us deeply realize the important role of structural reliability and safety,but because of its own composition of non-uniformity and discontinuity,the real damage situation and damage evolution process of concrete interior has been the focus and difficulty of scientific research.When concrete finite element modeling is used,some parameters of the actual structure can only be assumed and simplified according to experience,so there will be a large deviation between the structural response calculated by finite element and the actual test results.Based on the acoustic emission phenomenon of concrete(i.e.,elastic waves will be released inside the material during the damage process),this thesis collects the acoustic emission signals sent out by concrete specimens during the damage process,uses the quantitative relationship between the characteristic parameters of acoustic emission signals and the damage variables to modify the parameters of each element in the finite element model of the specimens,and establishes a finite element model more matching with the actual damage process.To analyze the actual damage evolution process of concrete structure,explore the real mechanical state of the structure and its evolution.The main research work of this thesis includes:(1)Based on the concrete failure process and continuous damage mechanics model,the relationship between AE energy,count and concrete damage variables is analyzed from the AE rate process model,and a quantitative relationship model between AE cumulative events and cumulative damage variables is established.Then,according to this model,an expression is established to describe the damage quantity corresponding to the unit event number.(2)Based on the relationship between the number of unit events and damage variables and the principle of equivalent strain,a concrete finite element model revision method based on AE parameters is proposed.The loading test of concrete specimens under uniaxial compression was carried out,and acoustic emission signal and other data were obtained.The finite element model of the specimen was established,and the AE signals emitted from each unit in the model were extracted by acoustic emission source localization method.According to the relationship between the number of unit events and the damage variable,the stiffness of each element in the finite element model is modified to realize the modification of concrete finite element model.(3)The analysis and comparison of the failure condition of concrete under uniaxial compression test and the experimental data with the calculated results of the revised finite element model show that the model is in good agreement with the actual test condition in the first half of the section,and the error in the second half is within 30%.