The Temperature Effect Research Of The Cable-stayed Arch’ Side Span Bridge Concrete Box Girder

Concrete box girder with its comprehensive advantages has been widely used inbridge engineering. However, as the bridge span is more and more large, the size ofbox girder cross section and the local volume become larger.The temperature field andtemperature stress caused by hydration heat and sunlight during the bridge operationalperiod more and more cause the attention of engineering circles.Exampled by the health monitoring project of a certain cable-stayed arch bridgein Xiangtan as the background, calculating and analysing the areas above on the basisof summarizing the existing research.On the hydration heat temperature field andstress field, using the hydration heat analysis module of finite element software MidasFEA to fully calculate the hydration heat temperature field and stress of X1#concrete’s block. Then studying the sensitivity of hydration heat temperature effectabout construction phase, template type and environment temperature.Afterwards,putting forward several measures to decrease the hydration heat effect. On thesunlight temperature effect, we select typical weather to test the temperature of sidespan box girder in the west bank. Getting the measuring point’s temperature changesthroughout the day and fitting temperature gradient mode of this box girdersection.Then using the finite element software Midas Civil to calculate thetemperature stress under this temperature gradient mode.Results show that during the hydration heat process of X1#concrete block,thestress of the areas including outboard wing flange、the junction of the flange plate andthe web plate、the external side of a base plate、the junction of the web plate anddiaphragm plate and so on exceed the limit tensile stress of concrete. The high stressarea on the outboard web inside the box girder and the location of web cracksobserved coincide to each other well. Rational delamination and subsection ofconcrete grouting blocks can effectively reduce the hydration heat effect and preventcracks. Using steel template instead of Wood formwork can alleviate hydration heateffect partly, but the effect is not obvious; If we pour the concrete in summer, thehydration heat temperature effect is very obvious.During concrete sclerotic process,the sharp decline of temperature can lead to the change of the temperature differenceand the crack areas are significantly more than the areas in spring and autumn. Thetemperature gradient model fitted according to the measured sunlight temperaturefield has a higher safety stock.The temperature stress caused by sunshine does not exceed the ensile ability of the structure. The research contents in this paper willprovide judgment basis for the causes of the crack in a certain cable-stayed archbridge in Xiangtan city and will guide the bridge monitoring in the future. At the sametime, it also provides a reference for similar project construction.