Damage Identification Of Beam Structure Based On Modal Information Entropy And Two-stage Information Fusion

In recent years,with the frequent occurrence of bridge engineering accidents in my country,the structural health monitoring system can timely assess the operational status of the structure,effectively avoid accidents,and provide a basis for decision-making for the maintenance and management of bridge struct ures.This is the focus of research in the field of civil engineering.On the one hand,damage identification is the core part of structural health monitoring.On the other hand,with the increase of the service life of the bridge,the damage accumulation of the bridge in the complex environment due to various uncertain factors may eventually lead to the bridge accident.Therefore,it is necessary to study the damage identification method of the bridge structure.This paper mainly uses the deterministic ide ntification method of beam structure curvature modal parameters combined with uncertain identification methods such as information entropy theory and information fusion theory to carry out damage identification methods,and proposes a damage identification method based on modal information entropy and two-stage information fusion,establish a finite element model,and verify the validity and reliability of the method through numerical simulation and theoretical analysis.The laboratory model verifies the en gineering applicability of the modal curvature entropy and the two-stage information fusion diagnosis method.The main work and research results of this paper are as follows:(1)Based on the theoretical basis of curvature modes,the modal curvature difference,modal curvature ratio,generalized flexibility curvature difference and information entropy theory are combined to construct the modal curvature difference entropy,modal curvature specific entropy,and generalized flexibility curvature difference entropy three indicators.Establish finite element models of simply supported beams and continuous beams through MIDAS/Civil,compare and analyze the damage results of traditional modal curvature index and modal curvature entropy index under different working conditions.Besides,different levels of noise are introduced to verify the noise resistance of the three curvature entropy indexes.The comparative analysis results show that the first three-order damage recognition effect and noise resistance of GFCDE index are significantly better than the other two indexes.(2)A deeper study of the damage identification of the bridge structure is introduced by combining the information fusion method of two-stage D-S evidence theory and the GFCDE index.The first three stages’ GFCDE index before and after damage is calculated by gaining the data from the established finite element model of simply supported beam and continuous beam.Taking the GFCDE damage identification result of each stage as a single information source,the damage of simply supported beam and continuous beam under different working conditions is identified by writing a MATLAB program based on GFCDE index and two-stage information fusion method.The fusion results show that when compared with results of using GFCDE index only,the fused information of the two stages improved the identification performance,and it bears qualities of accuracy and noise resistance.(3)The applicability of GFCDE index and the two-stage information fusion method in practical engineering is verified through the vibration modal test,which is carried out by hammering the simply supported steel beam.The damage degree is measured by the depth and width of the openings on the beam’s cross section,and the mode values and frequency values of the first three stages of the structure are obtained by using Coinv DASP MAS modal and dynamic analysis software.The final analysis and damage identification are carried out according to the steps of information fusion.The experimental result shows that the identification effect of the laboratory model proves to be better when it is carried out by means of the two-stage information fusion method based on uncertainty analysis,and it is instructive when put into practical engineering operations.