Research On Application Of Mobile Digital Image Acquisition Device In Structural Inspection

Civil engineering,as an important part of infrastructure construction,benefits from the development of Chinese economy and the research on engineering structure and materials,its scale and quantity are also increasing.As the time goes by,the existing structures are faced with the problems of aging and damage,which affect the performance and safety of the structure,and put forward requirements for the safety inspection of the structure.On the other hand,the research of structural forms and materials also require reliable and efficient equipment for testing.However,the traditional contact measurement(displacement gauge,dial indicator and strain gauge,etc.)and manual detection methods have the problems of large workload,small amount of data or high cost,which puts forward the demand for advanced structural inspection equipment.With the development of computer technology,modern photomechanical detection methods such as digital image correlation(DIC)and close-range photogrammetry are widely used in civil engineering,biomedical engineering,materials science and other fields due to their non-contact,nondestructive and high-precision advantages.Photomechanical detection methods have profound application value and broad development prospects.However,there are still some deficiencies: DIC equipment is usually composed of tripods and cameras,the measurement needs to be calibrated,and the equipment needs to be kept relatively still after calibration,which is less flexible;The target object is photographed by the staff holding a digital camera,and the offline measurement of close-range photogrammetry measurement is limited by the operator’s activity space.Therefore,the importance of mobilization of optical measurement technology is highlighted.This paper mainly studies the application of mobile image acquisition equipment in the inspection of civil engineering structures,designing relevant inspection methods,making mobile equipment,and further analyzing on the basis of inspection data.First,a method for detecting initial geometric imperfections of steel rack columns based on projected speckle correlation method is proposed.A handheld 3D scanner to was used to scan the steel rack column,and calculated the initial geometric imperfections by comparing the ideal geometric shape;then,a finite element model of the test piece was established based on the measurement data.Geometric imperfections are also incorporated into the ideal model of the upright in the FE nonlinear collapse analysis to study imperfection sensitivity and compare with the pointcloud model.The results highlight the sensitivity in selecting the imperfection mode shape and its magnitude using the traditional modal approach.An efficient measurement method for the initial imperfections measurement of complex cross-section specimens,which is beneficial to establish the steel rack columns’ imperfection database.Secondly,a method of topography measurement,damage inspection and positioning of the underwater bridge pier is proposed.An underwater climbing machine equipped with image acquisition equipment was developed,and the damage inspection of bridge piers was carried out by analyzing the images obtained by the image acquisition equipment.The method of pose estimation and adjustment of image acquisition equipment when working underwater is expounded,and the damage is detected by cylindrical fitting to the topographic data,and finally the disease is located by using the pose estimation results.It provides a realistic and feasible scheme for the damage inspection and positioning of underwater bridge piers.Finally,the joint displacement of the chord-supported dome caused by the prestressed tension was detected by using a SLR camera and a drone,the influence of the prestressed tension on the dome structure was analyzed.The limitation of operating space during the measurement of the dome structure and the difficultly of measuring top joints were efficiently solved.The displacement of the dome joints is calculated by comparing the spatial coordinates of the nodes before and after the prestress tension.On this basis,the influence of the prestress tension on the dome nodes is further analyzed.It has practical reference value for studying the prestressed tension of chord-supported dome,finite element modeling analysis and predicting the possible collapse result of the actual dome.