Field Monitoring And Numerical Analysis On The Temperature Of Long-Span Suspension Bridge

Temperature is one of the main environmental factors for the adverse effects of the bridge. Changing structural temperature and temperature distribution which are induced by external environment significantly affect the static and dynamic characteristics of bridges and force state of structures, contributing significantly to the consequent deterioration of the bridges. So the bridge bearing capacity is decreased and the safety is hard to be guaranteed. Moreover, service life is reduced. Even serious accidents are occurred. In this paper, a long-span suspension bridge is selected as the research object, based on its long-term health monitoring data collected by former researchers, study the law of temperature field on this type of long-span steel box girder suspension bridge with finite element numerical analysis method. The main contents are as followed:(1) Based on massive measured data,discuss the relationship between field test data of temperature, wind speed and wind direction in the mid-span and the data from nearest Meteorological Monitoring Station. Also, the variation law of each measuring point’s temperature, transverse and vertical temperature difference in the steel box girder section are obtained from the analysis of one-year monitoring data. The analysis results show that in the absence of measured data, it is available that using the data from near Meteorological Monitoring Station to analyzes the bridges’ temperature effect.(2) The effect of ambient temperature on static and dynamic characteristics of this suspension bridge(displacement, inclination ratio, natural frequency, damping ratio, etc) is studied and correlation analysis is carried out. It can provide reference for the design of structural health monitoring program and the analysis of temperature effect of bridge.(3) Finite element models of the steel box girder is developed by ANSYS. Based on environmental parameter, third type of thermal boundary condition is established. Time-dependent temperature fields of steel box girder under the action of solar radiation were analyzed. Compared with the measured temperature data, the calculation method proposed by the thesis is accurate. And temperature fields of main components in the bridge are analyzed too.(4) The most unfavorable distribution and the temperature gradient modes of transverse and vertical temperature difference in the steel box girder section are obtained from the calculation result by numerical simulation. Though the analysis, the steel box girder with inclined wed have larger transverse and vertical temperature difference. However, vertical temperature difference mode does not follow the mode from specification and the transverse temperature difference mode presents the “three ladder-like” characteristics.(5)Based on the relevant scholars’ experimental research, it is demonstrated that the numerical analysis method used to analyze the temperature fields of cable and hanger is accurate. Then, the temperature fields in the main cable and hanger of the suspension bridge under different conditions are analyzed and compared. The study shows that it is useful for decreasing temperature effect with the outer protective layer on the cables, and PE protective layer and grouting sleeve protection have the same effect on the temperature fields of the hangers.