Study And Application About Safety Monitoring Method And System Of Large Span Suspension Bridge

Currently China has come into the large-scale development period of of civil engineering construction. Anchored suspension bridge has become the most favorable competitors as a bridge span more than 1000 m because of its simple structure, unambiguous forceing and effective material useing. In China, the large scale, designing and construction of large-span suspension bridge have reached the world advanced level. Healthy and safe operation of large-span suspension bridges become a focus of attention. Large changes have occured in bridge monitoring software and hardware condition, which maked it possible for bridge health monitoring with sensing technology, data analysis and processing technology, computer network technology, system integration technology, bridge health monitoring on the sensing element and mass data processing problem have been resolved.As late start of large-span suspension bridges construction, the operation period of most large-span suspension bridges is less than two decades. Contrarily in Europe and the United States, the period is dozens or even hundreds of years and a mass of disease have appeared on the bridges which possibly menaced the structural safety.This paper carried out the following research contents:(I) Analysis of the influence factors of structural safety and research on the contents of safety monitoring system1. Analyse the influence factors of structural safety for the characteristics of the various components of large-span suspension bridge system, including: cable system, anchor system, the main tower system, stiffening girder system.2. Determine the large-span suspension bridge safety monitoring online contents and regular inspection contents according to the analysis of influence factors of structural safety and major diseases.(II) Study on safety monitoring system and monitoring instrumentality on existing large-span suspension bridge in operation1. Because of the short-term operations of large-span suspension bridges in China, we hane less accumulation of empirical data. This paper has investigated and analysed detailedly the technology condition and related safety monitor system techniques of large-span suspension bridge in Europe, United States and Japan during the operation of large-span suspension bridge.2. The main cable is the "lifeline" of large-span suspension bridge but depends on the open-examination which costs large of human and financial resources, impacts traffic and without an effective monitoring method. The hanging cable tension without long-term real-time online monitoring method and rely on regular inspection. Most monitoring systems still use the electric sensors. Large-span suspension bridge safety monitoring system is facing lack of real-time online monitoring methods of major technical indicators. (III) Study on long distance real-time and online monitoring FBG sensing technology of large-span suspension bridge1. The main cable wire strain and temperature monitoring system has been developed and combined with the main cable wire form and working condition based on FBG sensing technology.2. A new real-time online monitoring method of the hanging cable tension using FBG strain sensors and calibrated by vibration cable force sensors has been proposed, in allusion to the condition of hanging cable tension force has no long-term and real-time online monitoring method.3. According to the new prestressed anchorage system of suspension bridge which can be replaced without bond, a long-term monitoring method with FBG pressure sensor has been developed.The monitor method of anchor cable force is on-line and real time and make the anchorage system interchangeably.4. The tower and beam strain of largr-span suspension bridge has been monitored by using embedded FBG strain sensors and the FBG surface strain sensors. The temperature of the tower, beam, hanging cable and main cable were real time and on line monitored by special FBG temperature sensors.5. The high-speed FBG demodulation equipment combined with special FBG sensors were used in monitoring the fatigue stress of hanging cable, anchor cable unit, anchor box hanging ear.(IV) Study on the long term safety monitoring system with improved contents of large-span suspension bridgThe proposed FBG sensors have been used in the longterm health monitoring system of Wuhan Yangluo Yangtze River Highway Bridge which built an improved contents and large-scale long term real time monitoring system.The health and safety monitoring system of this bridge used large-scale advanced FBG testing technology. The subsystems are working properly and the data are accurate and effective by analysising the monitoring data of the subsystems.(V) Study on applied safety condition evaluation system of large-span suspension bridgeAccording to the actual needs of large-span suspension bridge safety condition evaluation, the evaluation strategy with combination of online monitoring and periodic inspection has been proposed. This strategy fullly used the function of long-term real-time online monitoring data and offline inspection data, and the evaluation standards and weigh of each level indicator have been determined. The safety condition evaluation system for Wuhan Yangluo Yangtze River Highway Bridge is developed. And the system provided reference for other large-span suspension bridges safety condition evaluation systems.