Research Of Bridge Damage Diagnosis Based On Information Fusion With Influence Line And Flexibility Matrix

To ensure the safe service of bridge structures,BDD(Bridge Damage Diagnose)and SHM(Structural Health Monitoring)have gradually become the research hotspots of scholars in a global context.These techniques have been applied to large-scale bridge structures,and the related research work has also made progress.However,there are still some unavoidable problems in the health monitoring and diagnosis of actual bridge structures.The boundary constraints of bridge structures are non-ideal,and the initial section parameters are uncertain.Bridge health monitoring systems rely heavily on the quantity and layout mode of response measuring points.Strong requirements of damage diagnosis results are subject to environmental noise.The studies on damage diagnosis of bridge structures are focused on the qualification and positioning stages,and it is relatively difficult to quantify damage accurately.In view of the above problems,this paper performs a research of bridge damage diagnosis based on hierarchical information fusion under quasi-static response.It is focusing on the following contents: In relation to the quasi-static influence line response of bridge structures,it considers the uncertainty with the sectional parameters of bridge structure models,analyzes the DIL(Deflection Influence Lines)and RAIL(Rotational Angle Influence Lines)of simply supported beam structures,and proposes the corresponding damage diagnosis methods.In relation to the non-ideality of the boundary support of actual bridges;it proposes a supporting beam model with elastic constraints,obtains the analytic expressions of its quasi-static DIL,RAIL and SIL(Strain Influence Lines)through solving the model,puts forward the related damage diagnosis methods,and offers a quasi-static loading test method considering the substructure of the equivalent boundary.Based on FCDR(Flexibility Curvature Difference Rate),it establishes damage assessment function and curve,proposes the dynamic indictors for bridge damage diagnosis based on FCG(Flexibility Curvature Gradient),and puts forward a damage diagnosis verification method considering modifications to the dynamic model for bridges.On the basis of the Dempster-Shafer(D-S)evidence theory;it proposes an information fusion method considering the spatial distance weighting coefficient of measuring points,puts forward the damage diagnosis method of hierarchical and spatio-temporal information fusion,offers several information fusion models,and integrates the quasi-static response and flexibility characteristic indictors proposed in this paper.Based on the above research contents,this paper mainly makes the following achievements:(1)The explicit expressions of DIL and RAIL are gaven for any section of the Benchmark model for simply supported beams.A quasi-static RAIL-based damage diagnosis method is further established,a quasi-static loading test method is proposed for the damage diagnosis of bridge structures,and the proposed method is verified through the examples of simply supported beam-based bridges and the damage identification test on simply supported beams.The proposed quasi-static RAIL method can position damage and calculate damage degree according to the flexural rigidity of the bridge structure section.The proposed DRAIL-C indictor has a better effect in identifying local damage close to measuring points.The obtained data when the measuring point of quasi-static rotational response is located at the seat have a better effect in diagnosing local damage than having its location close to the midspan.(2)A statically indeterminate supporting beam model with elastic constraints is established which has an uncertain flexural rigidity and contains the local damage.After that,a quasistatic influence line analysis on this model is performed and a corresponding damage diagnosis method is proposed.Through designing a test model for the vertical elastic supporting seat;it offers a quasi-static influence line loading method considering the substructure of the equivalent boundary,and experimentally verifies the supporting beam damage diagnosis method with elastic constraints.After that: the analytic expressions of quasi-static DIL,RAIL and SIL for the supporting beam with elastic constraints is established;the relations among elastic constraint rigidity,local damage parameter and the quasi-static influence line of any section of the main beam is revealed;an idea for mechanical analysis on substructure beams under non-ideal supporting is provided,and;a theoretical basis for the influence line analysis and damage diagnosis of assembly beam-type structures is offered.Through analyzing the quasi-static influence line of the supporting beam with elastic constraints,a damage diagnosis method for the quasi-static influence line response of bridges is proposed.The proposed method can be used to qualitatively and quantitatively diagnose bridge structure damage.However,its diagnosis results are subject to the positions of response measuring points.(3)On the basis of the D-S evidence theory;a hierarchical information fusion method is proposed considering the spatial distance weighting coefficient of measuring points,combines it with the quasi-static response information under multi-sensor mode to diagnose bridge structure damage,and puts forward four information fusion diagnosis models of different information fusion characterization levels.The damage diagnosis results characterize the certainty degree of damage occurrence at probability level via the mass function and use the damage diagnosis tests on simply supported beams and beams with elastic constraints to verify the effectiveness of the proposed damage diagnosis method.A method is proposed cconsidering the information fusion damage diagnosis of the spatial distance weighting coefficient of measuring points.This method can overcome the dependence of quasi-static response on a little measuring point,and weaken the influence of test noise and calculation error on damage diagnosis effect.Studies show that different information representation levels correspond to different damage diagnosis effects and that conducting information fusion diagnosis at higher information representation level creates a better effect than performing at lower information representation level.(4)Based on FCDR,damage assessment function and curves are established to calculate damage degree via the amplitudes of dynamic diagnosis indictors.It also extends the flexibility curvature matrix in the scalar field,solves the gradient vector of the central elements of the square-matrix scalar field,and further obtains the damage indictor of FCG.After that;it adopts actual bridge sizes for modeling,uses relative frequency error and model assurance criterion to revise the dynamic model for bridge structures,verifies the damage identification indictor of FCG based on the dynamic modification model,and employs an error model considering clipped Gaussian distribution to verify the noise resistance of new indictors.The FCDR-based damage diagnosis and assessment method present a satisfactory effect in the damage diagnosis of tied-arch bridges and ribs,and the FCG can still effectively quantify the relative damage degree at an error level of 10%,thus manifesting a relatively strong resistance to error interference.According to the results of damage diagnosis test,the flexibility curvature gradient indictor can effectively position and qualify damage,but its diagnosis effect still depends on the quantity and layout mode of acceleration sensors.(5)This paper puts forward a hierarchical spatio-temporal information fusion diagnosis method and establishes a hierarchical spatio-temporal information fusion framework and fusion diagnosis model.In solving the spatial misalignment of response information samples at different time sequence states,it proposes to adopt the linear extension method for processing spatial samples and linearly extends the dynamic indictors obtained via the measuring points of limited acceleration.This is to realize hierarchical spatio-temporal information fusion diagnosis.The spatio-temporal information fusion algorithm adopts the basic probability function of the damage information fusion at the corresponding unit as the damage indictor;to be able to diagnose the occurrence of existing damage,position damage and quantify damage degree in the damage diagnosis test on simply supported beams.It has also established four spatiotemporal information fusion submodels and applied them to the information fusion diagnosis of bridge structure damage.