Rapid Bridge Testing And Diagnosis Based On The Vehicle-Bridge Coupling Vibration Theory

China is in a period of rapid development of new urbanization and industrialization,and a large number of major infrastructure projects have been completed or are under construction.Meanwhile,the performance degradation of engineering structures gradually occurs under the action of environmental erosion,material deterioration,and daily service load and so on.In recent years,bridge collapse accidents occurred frequently at home and abroad,which caused significant economic losses and casualties and produced an extremely bad social impact.Therefore,it is a common topic at home and abroad to effectively maintain and manage the safety of large-scale and complex infrastructures.A large number of scientific research and engineering practices show that non-destructive evaluation and health monitoring technology can be used to detect the early damage and potential safety hazard of bridges,being an effective way to solve this problem.However,evaluating bridge condition based on regular inspection is mainly non-automated,time-consuming and laborious.It is difficult to analyze the structural damage from the massive monitoring data measured by bridge health monitoring system composed of various advanced sensors.On the other hand,the health monitoring system is expensive and difficult to be widely used in small and medium-sized bridges.With the development of automation and rapid testing technology,it has been gradually applied to detect bridge deck damage,bridge body cracks,broken cables,bridge pier sinking,etc.,which has significantly improved the test efficiency.In recent years,impact testing has been developed and applied in engineering practice,which has the advantage of identifying some more deep-level parameters by measuring the impacting forces and the structure responses,but it has not been widely used due to limitations in the excitation method and theoretical development.To solve this problem,this dissertation mainly studied the rapid test and diagnosis technique of bridges based on vehicle-bridge coupling vibration.The research content and innovation of my Ph.D works are as follows:(1)The general idea of rapid test based on vehicle-bridge coupling vibration is proposed,and the excitation equipment is developed.In order to solve the problem that the traditional force hammer or vibration exciter cannot effectively excite the vibration modes of bridges or the low efficiency in practical engineering application,this paper proposes a rapid bridge test method based on vehicle-bridge coupling vibration,which uses mobile vehicle instead of the force hammer or vibration exciter to directly excite bridges and monitor the wheel force and the bridge response in the test process.It is similar to the idea of impact test measuring both input and output at the same time.The load generating equipment is developed,which is suitable for the rapid test theory of vehicle-bridge coupling vibration.Through the integration of software and hardware,the vehicle integrates the effective excitation equipment and a complete set of control system,which can effectively excite the multi-order vibration modes of bridges and meet the requirements of the deep-level parameters identification of bridges.(2)A bridge rapid test theory based on vehicle-bridge coupling vibration is developed.The traditional impacting test method mainly uses force hammer or vibrator to impact the designated reference point on the bridge.In order to effectively excite the vibration of the bridge,the bridge is usually analyzed into smaller sub-structures the test data from all sub-structures could then be integrated.The relevant theories include the multiple reference method,the single reference method and the reference-free method.However,these test methods were not convenient because they all required an impact test to be performed on each sub-structure independently.In this paper,a rapid test method of bridge based on vehicle-bridge coupling vibration is proposed,which uses mobile vehicles to replace the traditional impact device.The mobile vehicle is changing in time and space on the bridge deck.Different from the traditional impact positions which are the discrete reference points on the bridge deck,the mobile vehicle acting on the bridge deck generates continuous wheel force along multiple axes at the same time.The traditional theoretical method is no longer applicable to this new implementation,so it is necessary to develop a set of theory which is applicable to vehicle-bridge coupling vibration for bridge test.By measuring all wheel forces,the coupled system can be decoupled into two systems,i.e.the vehicle system and the bridge system,which have the common excitation source that is the wheel forces.Then,the continuous wheel forces are allocated to nodes through load distribution function,including vertical nodal load and moment load,so that the bridge is a complex multi-input multi-output vibration system.Finally,the modal parameters and flexibility matrix are identified by using the displacement frequency response function matrix estimated from input and output data.The related theories include frequency response function extraction,singular value decomposition,enhanced frequency response function reconstruction,modal scaling factor identification,etc.The validity of the algorithm is verified by experiment and numerical simulation.Among them,the flexibility matrix obtained in this dissertation is the deep-level parameter of structure,which can reflect structural stiffness distribution and is an important parameter to establish damage index.Moreover,the identified flexibility matrix can be used to predict the deformation of structures under any static load.Based on the above description and combining the current bridge evaluation specification,a bridge' performance can be evaluated.(3)Based on the vehicle-bridge coupling vibration and the measurement of long-distance strain,a new rapid bridge testing method is proposed.In order to improve the performance of flexibility identification based on the idea of impacting test,a combined long-gauge strain flexibility and displacement flexibility identification method based on vehicle-bridge coupling vibration is proposed in this dissertation.This innovative method uses the mobile vehicle instead of the traditional force hammer or vibration exciter to excite the bridge,and uses the long-range strain sensor instead of the accelerometer.With this improvement,the vehicle-bridge coupling system is decoupled to an independent bridge system which is regarded as a linear time invariable system taking the wheel force as the input and the long-range strain as the output.This new technique takes the unique advantages of long-range strain sensing technology,which can realize the dual inversion of strain flexibility and displacement flexibility of bridges.Based on the above identified parameters,the index of damage identification is established.(4)Structure flexibility identification theory based on the improved Prony method is proposed.The accurate estimation of the structure flexibility matrix is very important for deflection prediction,damage detection,finite element model modification and other practical engineering problems.This paper presents a new method to estimate the structure flexibility matrix by using the input and output signals disturbed by noise.Firstly,the impulse response matrix of structures is calculated by using the collected impact force and acceleration response of a structure.Then the enhanced impulse response function is constructed by using the orthogonality of the displacement mode shape and denoised by Cadzow algorithm.Finally,the traditional Prony method is improved to identify the basic modal parameters and flexibility matrix of structures.The enhanced impulse response function has a unique advantage in the above modal parameter identification process.This construction reduces the multi-dimensional impulse response function to a single degree of freedom impulse response function in the space domain,and also reduces the multi-modal impulse response function to a single mode impulse response function in the time domain.It transforms the multi-degree-of-freedom multi-mode coupling problem into a simple problem which can only need to identify modal parameters of a single-degree-of-freedom single-mode system.This transformed system has merits for accurately identifying frequency,damping ratio,modal scaling coefficient of structures,and then gets the flexibility of a structure.Numerical simulation and laboratory experiments verify the correctness of the proposed method.Bridge rapid test based on vehicle-bridge coupling vibration was applied to an actual project.The developed test vehicle was applied to the tested bridge.As a comparison,the bridge under various working conditions was tested with force hammer excitation,including multi-reference point impacting test,moving continuous impacting test and vehicle-bridge coupling vibration.The results show that the test vehicle can easily and quickly realize the effective excitation of bridges,and meet the requirements of deep-level parameter identification.