Structural Damage Identification Of Bridge Based On Static Virtual Distortion Method

The virtual distortion method was first used for rapid structure re-analysis and then gradually developed for structural damage identification.However,the application of static virtual distortion method in structural damage identification is still limited to planar truss structures and bridge hangers.Therefore,this paper carries out a research on applying static virtual distortion method to identify the damaged beam elements of bridge structure,which further expands the application range of static virtual distortion method in structural damage identification.The main contents and conclusions are as follows:(1)Through introducing a strain transformation matrix into the existing theory of adopting static virtual distortion method for structural damage identification,the application range of this method is extended from planar truss and bridge hanger to beam elements of bridge structure.Three damage factor components,corresponding to three kinds of spatial beam elements distortion,are constructed.(2)The damage identification objective function of static virtual distortion method is rebuilt,and the simulated annealing method is introduced for its solution since the objective function variable has a feature of possessing specific upper and lower limits.In addition,the exact solution of the objective function is realized with an objective function solver written in MATLAB.(3)The planar truss finite element model is taken as an example to verify the feasibility of applying the static virtual distortion method to planar truss structural damage identification,and the applicability of using simulated annealing method for solving the objective function of damage identification.The results show that the static virtual distortion method is accurate in the damage identification of planar truss;and the simulated annealing method has good applicability in solving the objective function of damage identification.(4)Taking the finite element model of continuous beam as an example,six damage conditions with different damage degrees and damage locations are designed,and the process of using the static virtual distortion method for damage identification is introduced in detail.Also,the applicability and accuracy of static virtual distortion method for damage identification of three-dimensional beam element are studied in this paper.The results show that when adopting the static virtual distortion method in damage identification of continuous beam elements,the identified damage location and degree both have a high level of accuracy.(5)Taking an actual bridge as the research object,its damage identification elements are divided,the sensors are arranged,and a bridge static load test is designed according to the damage identification principal of the static virtual distortion method.Then based on the static loading test data and the solutions of finite element model,the damage degree of each element of the bridge hollow slab beam is calculated.Finally,the damage identification results are verified by the field observation.