Research On State Evaluation And Early Warning Method Of Bridge Structure Based On Monitoring Data

Many scholars at home and abroad have launched bridge structure state assessment based on global dynamic characteristics, but the monitoring of dynamic parameters is difficult to apply in the structural state evaluation effectively because of the complexity of the bridge structure, huge size, the insensitivity of local damage and the environmental factors. The structural condition assessment and early warning method based on the data of static monitoring are great significance for safety operation of the long-span bridges and one of present research hotspots in the field of civil engineering. Structural health monitoring system of the long-span bridges for ensuring bridge structural safety, applicability, durability provide a good platform. With the accumulation of real-time monitoring data, effective analysis and processing of large health monitoring data, the relationship between the establishment of environmental effects, the traffic load and the output state of bridge structure enhance the level of design and analysis of the bridge structure, which is the important field of health monitoring.This paper focuses on the correlation model between temperature of the bridge, the expansion performance of main girder, the static effect of strain and the environmental load of Dashengguan Yangtze Bridge based on long-term field monitoring data. The main work in this paper is as follows.1. Based on health monitoring system installed on steel truss arch girder of Dashengguan Yangtze Bridge, temperature differences from cross sections of top chord, arch rib chord, bottom chord and diagonal web member are specially monitored and researched through extreme value analysis, correlation characteristics analysis and probability statistics analysis. On this basis, the temperature difference between the standard value are simulated.2. By the structural health monitoring system on the Dashengguan Yangtze Bridge, temperature field data from steel truss arch girder and longitudinal displacement data from six groups of rubber bearings are collected. Using monitoring data, two correlations are investigated and revealed:the linear correlation between longitudinal displacement and temperature field (temperature and temperature difference); the linear correlation of longitudinal displacements in different locations. Moreover, multivariate linear regression equation is used to model the first correlation, and then Lagrange polynomial interpolation is utilized to model the second correlation, and the final mathematical model can be applied to simulate the longitudinal displacements of main girder at any location x and any time t with good effect.3. Taking advantage of the structural health monitoring system installed on the steel truss arch girder of Dashengguan Yangtze Bridge, the temperature field data and static strain data in certain months are specially chosen as training data, test data and assessment data. After the analysis of the training data, it is found that the global and daily trends of the static strain change are mainly caused by temperature, temperature difference and train. Train-induced static strains are filtered by removing decomposition coefficients of wavelet packet within their primary frequency bands to obtain the correlation between temperature field and its static strain, and the plotted scatter points of the correlation show apparent linear characteristics. Therefore, multivariate linear regression function combined with principal component analysis is used to model the correlation between temperature field and its static strain of training data, and the modeling test of test data indicates the effectiveness of the correlation model. Furthermore, residual static strains are adopted as assessment indicator and performance parameters of correlation models are assumed to increase by 20% each month to simulate trends of residual static strains under performance degradation, with three kinds of degradation regulations obtained after simulation. Finally the residual static strains of assessment data are calculated and the trends of their changes are compared with the degradation regulations, indicating that the static performance of Dashengguan Yangtze Bridge was in a good condition during that period.