A Temperature Distribution And Effect Research On Concrete Box Girder Bridge During Asphalt Paving

There is huge temperature difference distribution in the internal concrete box girder during asphalt paving,which may lead to cracks.In this paper,temperature distribution law of concrete box girder is analyzed by numerical simulation.Besides,the coupling stress,of the middle span under temperature load and construction machinery load,is calculated.Firstly,based on the transient thermal field theory and the heat-conduction theory,a 3-D temperature field model has been built,and validated by the measured results.In addition,the element deletion method was applied to simulate the paving construction process.According to the results,on the vertical side,the top of the even-adjusting layer,which is the center of the middle span of the bridge,reaches the highest temperature at 36min after the paving.Simultaneously,the maximum temperature difference occurs between the highest and lowest measuring points,when the structure undergoes the worse stress.On the transversal side,the temperature changing area of the concrete box girder lies in the region that is about 0.12m on both sides of the pavement edge;on the longitudinal side,temperature distributions of the concrete box girder in different cross-sections present a similar regularity.In addition,if the intervals between cross-sections are the same,the lag times of temperature distribution are the same.Secondly,by adjusting parameter selections,this paper explores the effects of the construction reason,paving materials,winds,etc.,on the temperature distribution of the concrete box girder during the paving were analyzed.The results show that construction season,paving materials,pavement thickness,the winds,solar radiation and the thickness of the even-adjusting layer have some effect on the paving temperature field.Therefore,the temperature effect in the concrete box girder during the paving could be reduced by the reasonable selection of construction conditions.A critical temperature gradient module affected by different variants has been made to quantitatively describe the change characteristics of temperature fields.At last,a mechanics model of a simply-supported girder bridge has been established to analyze the worst load case combinations of temperature load and construction machinery load,and to calculate the coupling stress in each case.It is showed that:by the coupling effect of temperature load and construction machinery load,there will be large transverse tension stress in the center of middle span of the simply-supported girder bridge,and large longitudinal tension stress in the bottom of the simply-supported girder bridge.In consequence,in relative parts of the middle span of the simply-supported girder bridge,potential vertical and transverse cracks should be avoided in the situation of asphalt paving.This research could offer references for the selection of temperature gradient of the concrete box girder bridge during asphalt paving,and the current standards of the temperature load.