Study On Long-life Pavement Structure Of Nrestressed Concrete Continuous Girder Bridge

In response to a national strategy of "traffic power",improving the capacity of transportation infrastructure to serve,in view of the mountainous area highway pavement anti-sliding performance decay quickly,the characteristics of relatively frequent maintenance,first in the long life road work table material selected,by use of 4x 30 m continuous prestressed concrete T beam as an example,the finite element software Abaqus is adopted to establish the bridge table long life road pavement structure three-dimensional entity model.Three kinds of bridge deck pavement structure such as common asphalt pavement,pure epoxy asphalt pavement,the lower common asphalt and the upper epoxy asphalt were selected to be involved in the study.Under three different working conditions of standard axle load,overload,emergency braking,thickness,modulus,bridge deck concrete leveling layer thickness on the mechanical response of pavement and the change rule were analyzed.Finally the paper proposed a bridge deck table long life road,typical structure and control parameters,in order to realize the deck structure,function,long life,reduce maintenance costs.The main research contents and conclusions are as follows:（1）On the basis of research and literature search,combined with domestic and foreign engineering cases,epoxy asphalt was showed significant performance through high temperature rutting resistance,interlayer shear resistance,low temperature bending,accelerated loading and other tests and verification.Compared with SBS modified asphalt,epoxy asphalt’s characteristics were substantially improved and finally selected as the long-life road surface material.（2）At the position of the most adverse load,the mechanical response results of bridge deck pavement under three working conditions of standard axle load,heavy load and emergency braking went as follows:Three kinds of bridge deck pavement structures: under heavy load,the stress and strain increase multiple,compared with the standard axle load,is equivalent to the overload coefficient;Increasing the thickness of leveled layer under standard axle load can significantly reduce the tensile strain of pavement layer and effectively improve the fatigue life,but changing the thickness of leveled layer has almost no effect on the shear stress.Therefore,it is generally recommended that the thickness of leveled layer should not be less than 10 cm,and should be greater than 12 ～ 14 cm.Common asphalt pavement structure: under three working conditions,with the increase of pavement thickness,the tensile stress decreases slightly,the tensile strain increases significantly,the shear stress increases first and then decreases,and the change trend is small;When the modulus of pavement increases,the tensile stress increases significantly,the shear stress increases slightly,and the tensile strain decreases significantly.The maximum shear stress is usually 2.5 ～ 4 times of the maximum tensile stress,and the potential failure mode is transverse fatigue cracking extending from the middle and upper layers to both ends of the upper layers.In addition,under emergency braking conditions,the stress and strain are 4 ～ 14 times of the standard axle load,which play a role in failure control,and the potential failure mode is transverse crack or shearing push.Therefore,it is not economical to increase the thickness of the pavement to prolong the durability of the bridge deck,which should be realized by improving the bond strength and shear resistance of the material.Pure epoxy asphalt pavement structure: when the thickness changes from 1cm to 6cm under three working conditions,the amplitude of tensile stress and strain changes less than 10%,and the change is small.However,under standard axle load and heavy load conditions,the shear stress increases significantly with the increase of the thickness.The shear stress of 6cm thick is about 3 times of that of 1cm thick.With the increase of the pavement modulus,the tensile stress and shear stress increase,but the tensile strain is almost unchanged.However,in the emergency braking condition,although the tensile stress,tensile strain and shear stress increase greatly,the amplitude is less affected by the modulus and thickness.Therefore,increasing the thickness and modulus of pure epoxy asphalt pavement structure has little influence on the force of bridge deck pavement structure,and the thin layer structure with a relatively low modulus and a thickness of less than 6cm should be adopted.Under the action of standard axle load and heavy load,the tensile strain of the structure is only 39～60% of that of the common asphalt structure with the same thickness.When the modulus of the lower layer increases,the tensile stress and tensile strain of the upper layer are almost unchanged,and the shear stress decreases.The tensile stress and tensile strain of the lower layer increase,and the shear stress is almost unchanged.Under the emergency braking condition,the thickness of the lower layer increases,the tensile stress and strain increase,and the shear stress changes little.When the modulus of the lower layer increases,the tensile stress of the upper layer decreases,the tensile stress of the lower layer increases,and the tensile strain of the upper and lower layers decreases,but the shear stress of the upper and lower layers almost does not change.Therefore,adding epoxy surface layer on the modified asphalt can greatly improve the fatigue performance,but too large thickness of the lower layer is unfavorable to the fatigue performance,and the thickness and modulus have little effect on the shear stress,so the modified asphalt with high modulus and thickness less than8 cm should be used as the bottom layer.（3）Combined with the mechanical response of bridge deck pavement structure,material properties and construction conditions,technology reliability,financial conditions,current situation,the pure epoxy asphalt and modified asphalt commonly used layer of epoxy asphalt layer above the bridge deck under the table structure were recommended as long life road.About two kilometers long and 2 cm test section were applied on the Moluo River Bridge and Longqing bridge of Yunnan Wutangxun highway according to study results.The scheme of 2 cm thick SBS modified asphalt stress absorbed layer + 2 cm thick anti-slide surfaces of epoxy asphalt was used and the test results meet the expected requirements.At the same time,according to the proposed three structure combination schemes,the whole life cycle cost analysis was carried out by considering the initial construction cost,maintenance cost,time delay cost and other factors.The results showed that the long-life road table structure has good economic benefits in the service life of 30 years.