Damage Identification Of Concrete Beam Structure Based On The Theory Of Modal Information Entropy

With the in-depth study of structural dynamics and damage mechanics,the understanding of the damage mechanism of concrete beam structures and the theoretical basis of damage diagnosis methods have been greatly improved.Among them,the structural damage identification method based on vibration information can judge,locate and quantify damage by measuring and analyzing the vibration response signal of the structure,and has been successfully applied to the damage diagnosis and health monitoring of many structures.This paper mainly uses the response characteristics of beam structure modal parameters to structural damage,combined with the significant effect of information entropy and utility information entropy on the nonlinearity of structural systems,a new damage identification index based on modal information entropy is proposed.The finite element simulation and model tests were used to verify the validity and reliability of the new index.The main research contents are as follows.(1)Based on the sensitivity of modal curvature index to structural damage,the utility information entropy of information theory is introduced into the damage identification of concrete beam structures,and the modal curvature utility information entropy index(MCUIE)is proposed.When calculating the probability term P in the utility information entropy of the structure,the modal curvature value of the beam structure is taken as the input parameter to calculate the local probability of the three adjacent nodes,and the change of the modal information when the damage occurs is reflected in the form of probability.the validity of the proposed index is verified by the finite element model of simply supported beam.(2)In order to verify the feasibility of the modal curvature utility information entropy index in actual engineering,a homogeneous steel beam with obvious deformation after stress was selected to make a simple supported beam model.By symmetrically cutting grooves of different depths to simulate damage conditions,placing an acceleration sensor on the beam to measure the vibration information of the structure,and using Coinv DASP MAS modal and dynamic analysis software to analyze the test signals.The test data were processed and calculated according to the calculation method of utility information entropy of mode curvature.(3)The flexibility matrix of structure has the common characteristics of structure mode frequency and mode shape,which can reduce the contribution of high order modes,and the generalized flexibility matrix can further reduce the contribution of high order modes.Combining the generalized flexibility curvature matrix with the information entropy which can effectively highlight the nonlinearity of the structure,the generalized flexibility curvature information entropy index(GFCIE)is proposed.The error distribution model following truncated gaussian distribution is used to verify the noise resistance of the index.The numerical simulation and experimental results show that MCUIE index gives full play to the advantage of the sensitivity of modal curvature to structural damage,and overcomes the disadvantage of modal curvature index by combining with the utility information entropy.It can effectively identify single-point and multi-point damage at different positions of the structure and has good noise resistance.The degree of damage of the structure can be qualitatively determined by fitting the relationship curve between the peak value of the MCUIE index and the degree of damage.The damage identification capability of MCUIE has also been verified by simply supported beam test,which can provide an effective solution for the damage identification of the practical engineering.The results of simply supported beam and continuous beam calculation examples confirmed that the GFCIE index can effectively reduce the truncation error caused by the higher order modes to improve the accuracy of damage identification of indicators.The GFCIE index is sensitive to damage conditions at single,symmetrical and multiple positions of the structure,and can effectively identify damage conditions where the noise level does not exceed 10%.