Performance Analysis And Evolution Of Continuous Rigid Frame Bridge Based On Long-term Health Monitoring Health Monitoring

Health monitoring is the indispensable component of the modern large-scale bridges andit provides performance, status and other scientific information for bridge design, construction,services and maintenance strategies. However, due to the health monitoring data often theresulted from the combined effects, the analysis and mining of the data becomes a challengingtopic in the whole world. This paper systematically summarizes the monitoring systems andthe research state of their performance analysis and safety evaluation of world-widelarge-scale bridges. Based on the health monitoring system of Zhaoqing West River Bridge,the thesis improves the centralized monitoring system, and deeply analyzes the monitoringdata and structural performance of Zhaoqing West River Bridge in service and solves somerelated key scientific problems. The main researches and results are as follows:According to the measured temperature data, the temperature variation of the concretebox-girder is analyzed in detail under the solar radiation and other natural conditions. Basedon the normal distribution probability, the representative values of temperature effect of thebox girder with asphalt layer is recommended; It is concluded that the vertical temperaturegradient of the concrete box-girder may be described in the form of combination of the powerand the broken line, and the temperature difference between the top deck and the base plate isproportional to the atmospheric temperature. The probability distribution of seasonaltemperatures is analyzed, and the maximum measured seasonal rising temperature is23.4℃and the dropping temperature is20℃during the service time of the bridge, which shows thatthe temperature difference used in bridge engineering design is too small in Guangdong.By the analysis on the monitored data and establishing the mechanism of selecting theeffective data, the concrete shrinking and creeping strains and their evolution in the servicebridge are measured successfully. After the technical characteristics and adaptability of threecommon shrinkage and creep models are analyzed, the CEB-FIP (1990) model is finallyrecommended for the calculations in the similar concrete structures. It is recommended tomodify the the shrinkage and creep model with effects of temperature by the age-equivalentidea. The shrinkage and creep of the concrete on the background bridge was analyzed with the model, and the results have good agreement with that from measurement.Based on abundant monitored strains, the difficulties are overcome from mechanism andalgorithm, which the monitored strains are coupled with multiple factors and the strainscaused by overloaded vehicles are small in a concrete bridge. A methodology is developed toidentify overloaded vehicles. Based on the analysis of the characteristics of long-termmonitored data, By taking the advantages of wavelet transform on detecting abnormal data insignal, the wavelet is used for identify abnormal data and location primarily, the change ofstrains at abnormal positions between adjacent signal is compared with the correspondingfinite element simulation value to determine it whether induced by overloaded vehicle or not.The capturing probability of the overloaded vehicles is derived, and the daily number ofoverloaded vehicles on the background bridge is estimated successfully. Based on Minertheory, the formula of the additional damage on the key portions caused by overloadedvehicles is derived. At last, based on extensive monitored data, the fatigue stress spectrumgenerated by overloaded vehicles and the additional damage of the background bridge in thedesigned benchmark period caused by overloads vehicles are estimated.By the use of the characteristics that the monitoring system covers the whole processincluding concrete pouring, solidification, construction and service, an algorithm is suggestedto convert the monitored strain into the stress of the bridge directly. Based on nearly five yearsof monitored strain data of the bridge, an evaluation method of localized time-dependentreliability is suggested, in which the monitored stress and strength of concrete in bridge aretaken as the load (S) and resistance (R) in the localized reliability functional functionrespectively. The load probability distribution and its variation with time (5years) are firstlyrealized from the long-term health monitoring in the world. By means of the localizedtime-varying reliability analysis of the bridge, not only the reliability of the bridge in thevicinity of the monitoring points can be assessed objectively, but also the variations of theirreliability with time can be demonstrated. Results show that this method can help bridgeengineers and managers to decide a bridge inspection or maintenance strategy.