Damage Identification Method Of Long-span Bridge Based On Generalized Influence Line Information Fusion

At present,there are still some difficult problems in the research field of structural health monitoring,such as the strong dependence of damage indexes derived from structural flexibility matrix on sensors,and the poor robustness of damage indexes derived from influence lines.How to quickly and accurately identify the damage location and degree of long-span bridge structure has gradually become a research hotspot at home and abroad.In this paper,"Research on Damage Identification Method of Long-span Bridge Based on Generalized Influence Line Information Fusion" was carried out.The structural vibration mode and frequency were extracted from the long-span bridge model of finite element,and the change rate index of flexibility curvature difference was constructed.Meanwhile,the difference curvature index of bridge structure displacement and stress influence line is extracted and established by quasi-static loading mode of influence line.Based on DempsterShafer evidence theory,a method was proposed to fuse the change rate index of compliance curvature difference with the difference curvature index of displacement and stress influence line,and the basic probability distribution function was constructed.Based on the information entropy theory,the sensitivity of influence line difference curvature index to damage was further improved,the generalized influence line information entropy index was constructed,and the generalized influence line entropy fusion index was constructed by Dempster-Shafer evidence theory.Based on the research contents of this paper,the main results are as follows:（1）Based on the flexibility matrix theory,the change rate index of flexibility curvature difference was constructed.MIDAS/Civil was used to establish the spatial finite element model of long-span suspension bridge,and different damage locations and degrees of suspender and stiffening beam members were simulated to verify the constructed index.When single-point damage or multi-point damage occurs in long-span suspension bridge structures,the rate of change of flexibility curvature difference can better locate the damage location and quantify the damage degree.This index shows good sensitivity to low damage degree of structure.When two kinds of components are damaged at the same time,it is found that the rate of change of flexibility curvature difference is more sensitive to the damage of the boom than the damage of the stiffening beam.（2）MIDAS/Civil was used to establish the spatial finite element model of long-span suspension bridge.By extracting the structural influence line and constructing the difference curvature of the influence line,the sensitivity of identification of different damage locations and degrees of longitudinal lower chord,inclined belly and suspender in the model was studied.Displacement and stress influence line difference curvature indexes can be realized only by a sensor suspension bridge structural damage location and quantitative,stress influence line difference curvature index of suspension bridge longitudinal lower chord single point and multi-point damage recognition effect is good,displacement influence line difference curvature index on longitudinal lower chord and longitudinal oblique abdominal rod damage identification effect is remarkable.Under the same damage degree,the sensitivity of damage identification is inversely proportional to the distance from the detection point to the damage.（3）Based on Dempster-Shafer evidence theory,a method was proposed to fuse the change rate index of compliance curvature difference and the influence line difference curvature index,and the method was verified by establishing a long-span suspension bridge model.The multi-source information fusion method based on Dempster-Shafer evidence theory can optimize the recognition results of most single damage identification indexes.The proposed multi-source information fusion method and mode still have good anti-noise performance when the noise of the example reaches 5%,and effectively improve the fault tolerance of single data to the index damage identification results caused by the influence of the surrounding environment,so as to improve the accuracy of the index damage identification results.（4）Based on the information entropy theory,combined with the structural influence line and Dempster-Shafer evidence theory,the generalized influence line entropy fusion index was constructed,and the spatial finite element model of long-span steel truss arch bridge was established by MIDAS/Civil to simulate different damage conditions,and the index was verified by method.The proposed generalized influence line entropy fusion index compares the influence line entropy index.The method is novel and the damage identification effect is reliable.The index can accurately locate the damage position of single-point and two-point of long-span steel truss arch bridge,and has a good anti-error ability,but when the error level reaches 10%,the anti-error ability of this index is weakened.The research results can provide theoretical support and method reference for rapid identification of damage status of long-span Bridges and accurate monitoring of structural health status by combining the respective advantages of influence line index dependent on a small number of measuring points and compliance index sensitive to small damage.Figure: [43] table: [13] reference: [72]...