Research On Visual Construction Monitoring Command System Of Precast Small Box Girder Bridge Based On GNSS

In recent years,with the continuous advancement of China’s urbanization process,the planning and construction of relevant highways and urban roads has spawned the demand for a large number of new bridges.Precast small box girder bridge is one of the most widely used bridge types in highway and municipal roads in China,but its beam erection construction mainly depends on manual observation and command.The current construction mode has some disadvantages,such as unstable command accuracy,high labor cost,low construction efficiency and potential safety hazards.Aiming at this phenomenon,this paper made a deeply study on the construction of a visual construction monitoring and command system of precast small box girder bridge based on GNSS positioning technology.In this paper,a precast small box girder bridge with span combination of 4×30m was taken as the research object.Firstly,the construction stage of the bridge was analyzed to grasp its construction characteristics and deformation characteristics,so as to provide a theoretical basis for the study of precast box girder posture positioning algorithm;Then,the design and development of visual construction monitoring and command system of precast small box girder bridge based on GNSS were completed;A scale test model of the intermediate beam of intermediate span hoisting construction of the bridge was designed and made,and the model beam hoisting test based on the system application had been carried out to verify the reliability of the system in commanding the beam erection construction.The main research contents are as follows:1.In order to provide a theoretical basis for the core algorithm research of system commanding hoisting construction,Midas/Civil and Midas/FEA were used to establish the frame finite system and solid finite element models of precast small box girder bridge respectively,and the static analysis and construction stage analysis were carried out: firstly,the reliability of the finite element model is verified by comparative analysis;Based on solid model,the deformation development characteristics and related influencing factors of prefabricated box girder in each construction stage before hoisting are studied.2.The functional requirements of the system were analyzed,and a multi-layer logic architecture based on software and hardware integration was formed.Combined with the application characteristics of GNSS positioning technology and the technical characteristics of lifting construction,the integration scheme and installation scheme of system hardware were designed,and the core algorithm of the system was deduced based on the scheme and the results of finite element analysis.Combined with the functional requirements of the software and the development characteristics of Unity3 D,the architecture design of the system software is completed.3.Based on the design scheme of system software,the precast small box girder bridge was taken as the simulation object,and the construction simulation scene was established with Unity3 D and Sketch Up.Aiming at the functions and application process of the system,various GUI controls were flexibly combined and applied to form a reasonable,simple and beautiful user graphical interface.Finally,C#programming technology is used to realized the functional modules of the software and completed the development of the system software.4.Taking the hoisting construction of the intermediate beam of intermediate span of the precast small box girder bridge as the test prototype,a complete set of scale test models were designed and made according to the geometric similarity ratio of 5:1.The visual construction monitoring and command system developed in this paper was applied to the hoisting test of model beam.The reliability of the practical application of the system was evaluated by observing the monitoring effect of the system on the hoisting attitude of the beam and the accuracy of the final command of the installation of the model beam.The test shows that the system can monitor the lifting attitude of beam in real time and accurately,and the measurement error of inclination Angle is less than 1°.The construction accuracy of the system command frame beam meets the requirements of the code.