Research On Damage Identification Method Of Beam Bridge Structure Based On Generalized Flexibility Curvature Matrix

As a key part of the structural evaluation of the health monitoring system,although a series of theoretical advances have been made in the damage identification method based on dynamic fingerprints,there are not many of them that can be truly applied to the identification of actual structural conditions.Most methods generally have shortcomings such as large errors and complex calculations,and even some methods are only effective under ideal conditions.Therefore,finding a method that is very sensitive to the location and degree of structural damage and has universal applicability is an urgent problem in dynamic fingerprint damage identification technology.Based on the summarization of the existing dynamic fingerprint damage identification theory,this paper proposes a new index for beam bridge structure damage identification based on the generalized flexibility curvature matrix.Finally,based on the test data of a three-span continuous rigid-frame real bridge,the numerical simulation and verification analysis of beam bridge structure damage identification with new indicators carry out by ANSYS and MATLAB.The main contents and conclusions are as follows:(1)A review of the current main structural damage identification methods,focusing on the four types of damage identification methods: frequency,modal curvature,flexibility curvature and modal strain energy,and the advantages,disadvantages and applicability of these methods are obtained through the damage simulation analysis of a simply supported beam bridge and a continuous bridge.The analysis of calculation examples also shows that the generalized flexibility can obtain high recognition accuracy using only two-order modal data.(2)Based on the generalized flexibility theory,a new damage index is constructed based on the generalized flexibility quadratic curvature matrix,that is,the diagonal elements of the generalized flexibility curvature matrix before and after damage,the 1-norm of the column elements and the 2-norm of the column elements,therefore,three new damage indicators are constructed.According to the damage quantitative formula of the curvature method,the relationship between the generalized deflection curvature index and the damage degree is determined.Subsequently,the simple supported beam and three-span continuous beam finite element model are used for verification.The analysis shows that these three new indicators can identify the damage location and damage degree of both single damage and multiple damage conditions,and comprehensive comparison shows that the generalized flexibility quadratic curvature matrix diagonal index(GFCCD)has the best effect.(3)In order to analyze the sensitivity and applicability of the GFCCD index,the damage of three different cross-sections of simply supported beams is simulated and analyzed.The results show that GFCCD is more sensitive than modal curvature index(MFCCN2)in terms of the sensitivity of variable cross-section damage identification.Good stability.Finally,the discussion found that the number of structural mode shape measurement points determines the recognition accuracy,and the normalization method only has a slight impact on the recognition of GFCCD damage degree.(4)In order to further discuss the actual effect of GFCCD index,combining with the detection data of a continuous rigid frame bridge,the benchmark model of the bridge is obtained through parameter modification.On this basis,the damage identification index proposed in this paper is used for damage verification analysis.The results show that for statically indeterminate beam structures such as three-span continuous rigid frame,the damage index GFCCD can identify the damage location and damage degree of the main beam.