Time Dependent Analysis Of Sunshine Temperature Field And Its Effect Of A Concrete Box Girder Bridge In Ningxia

Thin walled box girder is widely used in contemporary bridge engineering construction because of its excellent crossing capacity,large rigidity,small self weight and low cost.Due to the erosion of natural environment,the life of bridge structure will be affected by a variety of physical factors,including solar radiation,temperature changes and other temperature effects.At present,there is no uniform regulation on the temperature distribution mode of concrete box girder bridge in national codes.At the same time,different temperature distribution modes of regional climate conditions have obvious regional characteristics.However,it is still proposed that the influence of temperature on bridge structure can not be ignored,which is one of the main reasons for cracks in bridge structure.The distribution of temperature field of concrete box girder bridge in Ningxia is different from that in other areas under clear weather,which has typical climate characteristics.Therefore,it is of great significance to carry out the research on the temperature field and temperature effect of the concrete box girder bridge,so as to determine the temperature difference distribution mode of the actual situation of the variable cross-section concrete continuous girder bridge in the areas that meet the contract type,and to guide the subsequent design of similar bridges.The main work of this paper is as follows:1.Based on the calculation theory of variable cross-section concrete box girder,taking the Yellow River Bridge of Zhongwei South Station in Ningxia as an example,the simplified form of temperature field,the theoretical calculation method of temperature field and temperature effect are summarized.2.The calculation method of solar radiation based on ASHRAE clear sky model is analyzed.Combined with solar physics,meteorology,space geometry and other disciplines,the direct component values of solar radiation of 34 provincial capital cities in China are calculated under the condition of constant atmospheric extinction coefficient of 0.5.3.Using ANSYS large-scale finite element analysis software,the refined thermal mechanical coupling model of the middle span half of the Yellow River Bridge(continuous beam)at Zhongwei South Station in Ningxia is established in the form of APDL language,and the thermal parameters and the subordinate regions of thermal boundary conditions are determined;in the absence of sufficient definite conditions,the temperature fields of the top plate,web plate and bottom plate of the beam are obtained after loading in the way of equivalent heat generation rate Vertical,horizontal and vertical distribution law;temperature difference analysis is carried out,and compared with domestic codes,the rationality and limitations of codes are discussed,and the distribution of horizontal gradient temperature difference is supplemented;the concrete "heat preservation" phenomenon is briefly described;the typical location area is obtained by analyzing the gradient temperature difference curve at typical time,and the time-dependent characteristic analysis is carried out by taking this area as the research object Combining the eigenvalues,it is found that the maximum transverse gradient temperature difference occurs at 20 o’clock.4.The effect caused by temperature is mainly divided into stress and rotation angle.The results of the first principal stress at each time are obtained.The maximum first principal stress line is determined by controlling the section,and the curve form of the first principal stress line at each time is drawn.It is determined that the cusp will appear at the top plate,web plate and bottom plate with variable thickness,and the web plate thickness is unchanged while the section height and bottom plate thickness are unchanged The results show that the smaller the beam height is,the greater the principal stress value is;the greater the gradient temperature difference is in the same area at different times,the greater the principal stress value is;the closer the mid span section is,the greater the principal stress value is in different areas at the same time;the first principal stress peak of the roof appears at 15,while the web and floor lag behind the roof at 17,which is basically consistent with the time when the maximum gradient temperature difference appears;The results show that the roof curve is steep,the web is slow,the rise and fall of the main stress of the roof is very obvious,and the difference of the main stress of the roof,web and floor at the same time gradually decreases after 15o’clock.The close relationship between the angular displacement of the cantilever end of the roof and the solar time angle is discussed.