A Reference-pressure-based Bridge Delfection Monitoring System And Its Performance Analysis

Along with the growth of the age of bridges, the problems of down deflection ofbridges are inevitable, in order to prevent the destruction of the bridge structures whichare deflected sharply, the long-term deflection monitoring of bridges is necessary. Inview of the importance of bridge deflection, many measurement methods of bridgedeflection have been developed at home and abroad, and every measurement methodhas its own features and scopes of applications. Among these deflection measurementmethods, the connected-pipe-based deflection measurement technologies are usedwidely, but these deflection measurement systems have some errors because they arevulnerable to some factors, such as, the flow characteristics of liquid, the material andsize of connected pipe, liquid density, and acceleration of gravity. Therefore, this papersummarizes the state-of-the-art of bridge deflection measurement methods firstly, andthen, presents an improved, semi-closed, and reference-pressure-based bridge deflectionmonitoring system, which is developed on the basis of existing connected-pipe-baseddeflection measurement methods. The innovation of this paper focus on the designmethod and measurement principle of this presented deflection monitoring system,which can monitor the bridges’ deflection self-calibration and self-adaptively based ondouble basic point calibration method. The main research works are as follows:(1) Design the regular configure scheme and improved scheme of the system,introduce the measurement principle and method, analyze the system characteristicstheoretically, and explain the possible system errors and corresponding correctionmethods.(2) Accomplish the system components and software development, introduce thefunction parameters of pressure sensors and DTU (Data Transfer Unit), develop acentralized controller, discuss the working process of every device, and point out themajor functions of every software module.(3) Design and implement a series of experimental tests, introduce the testpurposes, processes, results and analyses, do some experimental verification accordingto the system performances, including the accuracy, stability and reliability, and drawsome valuable conclusions finally. (4) This system has applied to six prestressed concrete continuous rigid framebridges in Yunnan Baolong Highway. In this study, I introduce the design proposal ofthis practical project, do effective analyses according to some monitoring data, andverify the practical performance of this deflection monitoring system.(5) According to the system errors and gross errors of pressure sensors, this paperemploys relative systematic errors to correct the measuring results, and introducescommon judgments and processing methods for gross errors.In summary, the results of experimental tests and engineering applications candraw following conclusions: The measuring accuracy of pressure sensors can reach0.0001KPa; The presented system can monitor the short-term and long-term staticdeflections of bridges; The calculative accuracy of bridge deflections can reach0.001cm;The system has a certain degree of reliability and stability; If the system combines withsome appropriate pressure sensors, centralized controller, DTU and the solar poweredtechnology, it can also monitor the deflections of the bridges which are in remoteareas, complex terrain, large longitudinal slope and high fall bridges, and oblique andcurved bridges. The system can measure the dynamic deflection of bridges in theory,but in practical applications, considering of the anti-vibration and anti-jammingcapabilities of pressure sensors, the system can only measure the static and dynamicdeflections of the ultra-low frequency bridges, but it’s not appropriate to monitor thedeflections of the excessive vibration frequency bridges.