| Health monitoring of structures in service plays an important role in ensuring the safety of the people’s lives,property and the structure,in which structural damage detection is one of the core technologies.The damage detection method directly using vibration response has attracted much attention,as it does not require an accurate finite element model of the structure to be established and can avoid the need for complex modal identification.Accurate acquisition of structural vibration response data is the basis of this method.In this paper,the vibration-response-based structural damage detection methods are summarized and studied.To overcome the shortcomings of traditional contact response measurement methods,such as limited sensor installation,high cost,difficult synchronization and low efficiency,combined with the response acquisition technology of computer vision,a damage detection method using auto correlation function of response is proposed for the non-contact health monitoring of structures.The main contents of this paper are as follows:Firstly,the expression of cross-correlation function of structural response(displacement,velocity and acceleration)under sinusoidal excitation is derived from vibration theory,and the relationship between these cross-correlation functions is revealed.An Auto correlation function at Maximum point value Vector(AMV)based damage index is established from the response of each measuring point of the structure.The sensitivity expression of the AMV-based damage index to the local stiffness is derived using the partial derivatives of the modal parameters(frequency,mode shape)to the local stiffness.It is found that the response type doesn’t affect the damage localization ability of the proposed damage index.Secondly,the sensitivity analysis results of the 12-story shear frame structure show that the AMV-based damage index will have a sharp change near the damage location,indicating its sensitive to the damage location.The damage detection results of single/multiple damage at different positions of the frame structure show that the AMV-based damage index is adaptable to different types of responses that it can not only accurately identify and locate the damage under the influence of noise,but also reflect the severity of damage.In addition,the good consistency between the sensitivity analysis results and the damage detection results shows the effectiveness of the AMV-based damage index,and reveals the internal mechanism of its ability to locate the damage.Then,the phase-correlation-based templated matching method is applied combined with the local up-sampling interpolation method to obtain the subpixel displacement,such that the program is developed to calculate the structural response from the video data directly.The vibration measurement experiment of a cantilever beam shows that the non-contact method has high accuracy and fast calculation of the vibration response.Finally,the computer vision is integrated with the AMV-based damage detection method,and the structural health monitoring experiments are carried out on the 6-story shear frame with the highspeed camera and the truss bridge with the smartphone,from which the results show that the proposed AMV-damage index has good applicability to different response acquisition instruments and different structures.The structural health monitoring method using non-contact dynamic measurement response is established in this paper.Compared with the traditional method,it has the advantages of no need to install contact sensors,low cost,synchronous acquisition,etc.,and can directly use the response signal for damage detection with a high computational efficiency.The research results of this paper are helpful to enrich the related technologies such as structural dynamic response processing and damage detection,to expand the application of computer vision in structural health monitoring,and have a good application prospect for improving the safe operation of structures. |
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