| With the rapid development of our country’s economy and technology,more and more construction projects will face complex terrain conditions such as the big river,bay and gully in the process of continuous improvement of traffic infrastructure.The general small and medium-sized bridges can’t meet the needs of construction.The construction of large-span bridges becomes necessary,and the long and large span bridges are often complex,expensive,difficult to construct and difficult to maintain and manage,making the construction and maintenance technology of long span bridges become a national science and technology representative.At present,many domestic long span bridge list top position in the world,such as Runyang Bridge,Jiangyin Bridge,Tsing Ma Bridge,Sutong Bridge.Long span bridge is located in the important traffic area,contact the regional economic development.It has great engineering significance.Long span bridges under the complex environmental effects such as vehicle load,wind load,solar radiation,erosion and corrosion will lead to the performance degradation and structural damage after long-term service,which will affect the security service and life time of long span bridges.Therefore,the structural health monitoring technology has been introduced into the monitoring of the daily operation of many long span bridges.The purpose is to ensure the safety of the bridge structure during operation and detect the damage of the bridge structure.At the same time it also can evaluate the current performance status of the bridge.Long span bridge structure health monitoring system has a large number of sensors and massive daily monitoring data.Now there are many vibration-based damage identification methods and threshold warning methods,and many scholars found that the impact of temperature on the long span bridge is very significant.The temperature effect analysis of the long and long span bridges based on the monitoring data is still very limited.The influence of the longitudinal temperature gradient is often neglected.Environmental temperature especially the sunshine temperature causes non-uniform temperature gradient in long span bridge structure,which often produces a larger deformation and the temperature stress inside the structure.Its influence even more than the daily operation of vehicle load.Therefore,it is of great significance to analyze and evaluate the temperature and structural safety performance of long span monitoring data based on long span bridge structures.The main research contents of this paper are divided into the following parts:Firstly,the effects of temperature on the vertical displacement of the box girder,the longitudinal displacement of the beam end,the displacement of the tower,the cable force and the strain of the box girder are studied respectively.Analyze the vertical,horizontal and longitudinal temperature gradient of the bridge.The EMD method is used for measured strain decomposition.The linear relationship between temperature and temperature strain is analyzed,and the relationship of temperature,constraint strain and temperature displacement is revealed.The temperature stress of the structure under the linear gradient temperature and the nonlinear gradient temperature is calculated,and the concept of temperature-related total stress is defined.The stress and temperature-related total stress of the real bridge are calculated and analyzed statistically.Then,according to the actual monitoring data to evaluate the solar radiation intensity,and solar radiation coefficient is defined,and improve the solar radiation calculation model.Considering the temperature gradient along the longitudinal direction of the bridge,a pattern of longitudinal temperature distribution along the bridge is proposed.The longitudinal stiffness of the beam end and the damping effect of the viscous damper are analyzed.The three-dimensional temperature field and stress of long span bridges are simulated and analyzed by ANSYS.Finally,by analyzing the frequency variation and bridge shape change during the long-term service of the bridge to evaluate the bridge performance degradation.And the performance status and the expected life of the beam-end expansion joint are evaluated by analyzing the cumulative displacement of the beam end.The strength utilization factor and the temperature-related total stress strength utilization factor are calculated to assess the long-span bridge security status in the process of long-term service. |
