Research And Implementation Of Online Monitoring System For Bridge Deflection Based On Segmented Catenary Datu

Deflection is one of the main testing contents of bridge health monitoring systems and an important basis for evaluating the operational status and safety of bridges.For the widely used large-span prestressed concrete box girder bridge,the deflection of the main girder is a common phenomenon,and it will continue to increase with the growth of the service life of the bridge,resulting in a series of problems such as beam stiffness reduction,concrete cracking,etc.Therefore,it is very necessary to conduct long-term observation of the deflection.There are many types of existing deflection monitoring methods,but there are also common drawbacks such as high cost,complex installation,and insufficient measurement accuracy.Based on this background,this paper proposes a box girder deflection monitoring system,which takes segmented catenary as the benchmark,combines high-precision laser rangefinder and Lo Ra wireless communication technology,and carries out experiments and theoretical analysis on its testing effect and influencing factors.The main work of this article is as follows:(1)Design of a bridge deflection monitoring system.Fully consider the monitoring principle and installation environment of the monitoring system,design and select the segmented catenary reference module,deflection measurement module,data acquisition and processing module and other supporting equipment to ensure that the monitoring system can meet the use requirements.(2)Experimental verification of the effectiveness of monitoring system testing data.The experiment adopted a beam bridge model with a span of 4m,on which a monitoring system and a dial gauge were installed.Then,the model was graded and loaded.The deflection values measured by the monitoring system at all levels were compared with the test values of the dial gauge,and the results showed that the two were very close.The experiment also collected monitoring data for a long period of time(90 days)when the bridge model remained in a specific state,and found that its fluctuation amplitude was very small.The experiment shows that the deflection monitoring system has high accuracy and stability.(3)Analysis of influencing factors of monitoring systems and research on methods for correcting monitoring data.The main factors affecting the monitoring system are analyzed,and the method of using the finite element software to establish the catenary model to modify the monitoring data is proposed.When horizontal displacement occurs at the end of catenary,whether the catenary alignment calculated by ABAQUS modeling is consistent with the test is discussed.The results show that the factors affecting the monitoring system can be analyzed by establishing ABAQUS model.(4)Taking a continuous rigid frame bridge as the research object,the finite element models of the bridge and catenary are established according to the design parameters of the bridge,and the effects of the elastic modulus of the catenary,the angle of laser penetration and temperature on the monitoring data are analyzed.The results show that the impact of laser incidence angle on the monitoring data can be ignored,the elastic modulus of catenary should be measured before the installation of the monitoring system,and the temperature has a greater impact on the monitoring data.By further studying the impact of temperature,a detailed correction method for monitoring data during the working process of the monitoring system is provided.