Temperature Distribution Of Orthotropic Steel Deck Box Girder During Asphalt Concrete Pavement Paving And Its Influence On Structures

Asphalt concrete(AC)pavement is widely used in medium and small span steel municipal bridges.The temperature effect generated by high-temperature AC paving will cause displacement and deformation in the steel box girder bridges,and the corresponding secondary internal forces will be produced when the displacement is restrained.This kind of temperature effect has limited impact on long-span bridges,but it cannot be ignored for small and medium-span bridges with relatively strong constraints and high stiffness.In order to analyze the structural response of different types of bridge structures,the finite element simulation technique was used to analyze the temperature effect during AC pavement paving,and the mechanical response of different structural types of bridges was analyzed during AC pavement paving.Based on the finite element theory of heat transfer,the geometric conditions,physical conditions,initial conditions and boundary conditions of the definite conditions of the temperature field are established.The transient heat conduction models of twin box steel girder and flat steel box girder were established by ANSYS,and the birth-death unit technology was applied to simulate the paving construction process.During the AC pavement paving,the spatial and temporal temperature distribution characteristics of the steel box girder were analyzed.The results show that the AC paving side has little influence on the non-paving side,and the temperature distribution characteristics of the top deck are mainly related to the order of AC pavement paving and the state of the air in contact with the top deck.For the stiffened plates,the temperature drop rate of U-rib in box is slowest,and the temperature peak of the U-ribs at the top of the roof of the box is the largest.In order to analyze the response of different types of bridge structure more conveniently,the temperature gradient calculation model of the two types of box girders during the AC pavement paving was established.According to the spatial and temporal distribution of the temperature field of the steel box girder,the temperature field of the steel box girder was mathematically described by the temperature of the top deck and the U-rib web.The applicability of the formula for calculating the temperature load in beam element model was discussed by using the thermal-structure coupling model.The results show that for the twin box steel girder bridge,the calculation error of the longitudinal displacement,the vertical counterforce of the bearing and the vertical displacement of the beam body is less than 10%,and the calculation error of the vertical rotation angle of the bearings is larger.For the flat steel box girder,the beam element model can accurately reflect the change tendency of the structural response of the bearing at the paving side,and the calculation error of the bearing displacement and the mechanical response is more than 10%.The thermal structure-coupling model can be used to analyze the temperature field and temperature effect during AC pavement paving with different construction methods under different environments in different cross section bridges.The temperature gradient calculation model of twin box steel girder in this paper can be used to analyze the response of bridge structure during AC pavement paving.The calculation model of temperature gradient of flat steel box girder can be used to roughly analyze the structural response of bridge during AC paving.In order to analyze the mechanical response of different structural types of bridge during AC pavement paving,space pole department models of simply-supported,continuous girder bridges and self-anchored suspension bridges were established respectively,and the influence of AC pavement paving on bridges was analyzed using the temperature gradient calculation model.The results show that for the simple-supported beam bridge,the longitudinal displacement and the vertical rotating angle of the bearings are proportional to the span,and the peak value of each response appears before the completion of the AC paving,in which the vertical rotating angle of the bearing is the controlling factor.For continuous girder bridges with the same number of spans,the longitudinal displacement and vertical rotating angle of the bearings are directly proportional to the span,and the increment of vertical counterforce is inversely proportional to the span.The maximum longitudinal displacement of the bearing of the three-span continuous beam bridge is more than 2.2 times that of the 2-span continuous beam bridge,and occurs at the beam end bearing,in which the longitudinal displacement of the bearing and the bearing counterforce are the controlling factors.In the process of AC pavement paving,there will be a large tension in the paving side of the tower of the self-anchored suspension bridge,and the bearing tension is the control factor.Different types of bridges have different mechanical responses and different control factors during AC pavement paving.The temperature generated during AC pavement paving will have a negative effect on the bridge and should be paid attention to.