Development Of The Cable-stayed Bridge Monitoring System Based On Virtual Instrument Technology

When evaluating the cable-stay bridges’ structural state, Cable force is one of themost important parameters. This paper observing, analyzing and evaluating the backstaycable to master the healthy status of cable-stay bridges’ backstay cable. Usingmonitoring system to diagnose the structure in real time will recognize structure damagetimely and evaluate the safety of structure and these will be significant for puttingforward maintenance decision and extending the structure life.Along with the development of the communication and computer technology,virtual instrument as a comprehensive electronic measurement has been constantlyimproved and it’s gradually become the development direction in the field ofmeasurement and control. Using virtual instrument technology for large structuralhealth monitoring has become the focus projects in the field of civil engineering.Based on Chongqing Lijiatuo Changjiang River bridge, the cable force ofcable-stayed bridge monitoring system based on virtual instrument technology isdeveloped. The paper mainly focuses on the following aspects:Firstly, introduces common cable test methods, and selects random vibrationfrequency method based on environment as the main theory for system development.Uses the string theory to deduce the fundamental frequency calculation under theinfluence of cable sag and bending stiffness, and analyzes the effect of bendingstiffness, cable sag and added mass on measurement precision.Secondly, selects frequency difference method to calculate the fundamentalfrequency based on different frequency relations, discusses the precision and applicationrange and sums up the algorithm.Thirdly, applies the virtual instrument technology into the construction anddevelopment of cable force monitoring system and designs the overall structure of thesystem according to the design principles and requirements. The computer hardwareconfiguration and monitoring system software based on LabVIEW are realized.Lastly, uses the monitoring system to remote monitor the cable force of ChongqingLijiatuo Changjiang River bridge. The measurement results are reliable and can reflectthe changes of cable force accurately. The methods is worth to popular and apply inengineering practice.