Research On Installation Accuracy Inspection Method Of Spherical Hinge System Of Swivel Bridge Based On Three Dimensional Laser Scanning Technology

In recent years,with the increasing maturity of bridge swivel construction technology,the scale of swivel bridges built in China has been expanding.The spherical hinge system is the core structure of the swivel bridge,and its installation and construction accuracy directly determines whether the bridge can be safely and smoothly rotated.Presently,the installation and construction technology of the spherical hinge system is rudimentary,and there is no fast and efficient detection method to detect whether the lower spherical hinge,slideway and slider in the structure meet the design and usage requirements after installation,which is easily restricted by human factors.As a new type of surveying and mapping technology that emerged in the 1990s,Three dimensional laser scanning technology(TLS)has been widely used in engineering measurement,heritage conservation,spatial information monitoring and other fields due to its non-contact,instantaneous,efficient and other unique advantages.The application of TLS in the field of installation and verification of the spherical hinge system of the swivel bridge will provide reliable and accurate information of spherical hinge installation in a more efficient way.This paper relies on the research project of "New Urbanization Construction Project in Changchun New District(Phase One)-Research and Test on Swivel Spherical Hinge of Overpass Project on Xingfu Road across Beijing-Harbin Railway" commissioned by China Railway Shenyang Bureau Group Technology Development.Based on reading a large amount of literature and comprehensively discussing the current status of the spherical hinge installation technology of the swivel bridge,this article analyzed and explored the influencing factors of the point cloud data accuracy of the 3D laser scanning technology.The Free Scan UE type handheld 3D laser scanner was used to study the point cloud data acquisition technology of the spherical hinge system scaled-down model,and the Geomagic series software was employed to preprocess the acquired point cloud data of the spherical hinge system and analyze the accuracy.A new program was written in Matlab to detect the accuracy of the slider installation in the spherical hinge system for the shortcomings of the existing software.The main research contents and results are as follows:(1)The optimal scanning parameters for the spherical hinge system were obtained by analyzing the effects of the material and color of the object under test,the scanning weather and time,and the scanner resolution on the number of point clouds and the time required for scanning through simulation tests.The results show that the weather is cloudy,or sunny with the highest scanning efficiency from 7:00-9:00 and 15:00-19:00.Due to the large engineering structure,the resolution of the scanner can be chosen as 1mm,or 0.8mm or 0.5mm if high accuracy is required.(2)The scaled-down model of actual engineering spherical hinge system was designed and produced,and the point cloud data was acquired for the model.The Geomagic Wrap software was employed for point cloud pre-processing,including data reduction,deletion of solitary points outside the object,point cloud wrapping,spikes deleting,hole filling,grid doctor and other operations to obtain an accurate triangular surface piece model.(3)The Geomagic Control X software was utilized to analyze the installation accuracy of the spherical hinge system,including surface fitting,comparative analysis,etc.The results show that the technique in this paper can effectively and quickly achieve the measurement and adjustment of the concentricity deviation,parallelism deviation of the lower ball hinge and slideway and the slider installation accuracy until it meets the design requirements.(4)A more intuitive test program for the installation accuracy of the slider was compiled using Matlab,and the feasibility of the program was verified through an example.The feasibility of the test method for the installation accuracy of the slider was verified through the axial compressive stress test.(5)Combining the conclusions of the above simulation experiment and the analysis of the installation accuracy of the scaled-down model,a set of efficient and feasible spherical hinge system installation and construction technology detection methods were proposed,which provides a reference standard for the detection of the installation accuracy of the spherical hinge system of the swivel bridge in actual projects.