Field Measurement Analysis Of Temperature Field And Its Effect In Asphalt Paving Of Concrete Box Girder

Aiming at the problem of bridge cracks caused by the difference in temperature gradient of asphalt paving,the concrete box girder bridge of "Zhongwei South Station Yellow River Bridge" was taken as the research object,and the finite element program Ansys was used to establish a three-dimensional solid element model to analyze the concrete box girder in Ningxia.For the temperature effect of asphalt paving,the actual bridge construction conditions are used as the model boundary conditions,and the model is corrected after comparing and analyzing the measured data,and the temporal and spatial distribution of the temperature field of the concrete box girder under hightemperature asphalt paving is studied.The main research contents and results are as follows:(1)Study the influence of wind speed,initial beam temperature,atmospheric temperature,asphalt cutting temperature and asphalt paving thickness on the temperature field by changing the parameter values.The results show that: the above factors will affect the paving temperature field,so it is necessary to choose a suitable paving construction environment to reduce the temperature effect of asphalt paving.(2)Using the results of parameter analysis combined with the measured data of the actual bridge to fit the asphalt paving temperature gradient pattern in Ningxia,supplementing the bridge and culvert specifications;calculating according to the actual construction boundary conditions,the exponential function is used to fit the box girder span The vertical,horizontal and longitudinal temperature gradient modes of the section are used to obtain the temperature gradient distribution of the high-temperature asphalt paving of the Yellow River Bridge(continuous beam)at Zhongwei South Station.The temperature gradient distribution model in the specification is supplemented and perfected.The empirical parameters in the temperature gradient formula vary with different regions and bridge types,which also reflects the obvious regional characteristics of temperature.(3)The life and death unit method is used to simulate the asphalt mixture split-width paving construction method,and the horizontal and vertical temperature distribution rules of the mid-span section under the split-width paving method are studied in detail,and the conclusion is that(1)Use the split-width paving method as much as possible For asphalt paving,the bituminous heat carried by section paving is relatively small.(2)The secondary heating of framing paving affects up to 20 cm in the transverse direction.When designing the bridge deck,an isolation belt can be added between the motor vehicle lane and the non-motor vehicle lane,which can not only reduce the secondary heating temperature effect of asphalt slicing paving,but also enable motor vehicles and non-motor vehicles to drive in separate lanes to improve The safety of road traffic has been improved and the traffic order has been improved.(4)Establish a mechanical model of concrete cantilever box girder.The study found that during the entire process of asphalt paving,the maximum stress has always appeared in the mid-span section.In the process of high-temperature asphalt paving,the vertical and transverse directions of the mid-span section(box girder web,roof)are prone to compressive stress,and the compressive stress first increases and then decreases.As the asphalt slowly cools down,the temperature rise of the box girder roof also slowly decreases,the deformation also gradually decreases,and the compressive stress also decreases.At the same time node,the longitudinal stress Sx and the transverse stress Sz under the framing paving are much smaller than the longitudinal stress Sx and the transverse stress Sz under the one-time paving.(5)Calculate the change of the maximum tensile stress of the box girder under different paving modes and find the best paving mode.The results found that: the split paving method is the best way to pave the non-motor vehicle lane and then pave the motor vehicle lane after 24 hours.The temperature effect of the box girder under the hightemperature asphalt paving under this paving mode is the smallest.