Analysis Of Temperature Effect And Shear Lag Of The Main Girder During The Construction Stage Of A Cable-Stayed Bridge With Hybrid Girder

Compared with the traditional integral box structure,the separated steel box girder has been widely applied in long-span cable-stayed bridges in recent years due to its superiority in structure and weight.But the cross-section temperature distribution and the shear lag effect due to the temperature caused by the separation of the box and the increase of transverse width are more complex.It is necessary to further study the influence of the structure's stress and deformation.Taking a super large bridge in Foshan as the engineering background,the temperature field,the temperature effect and the shear lag distribution law of the separated steel box girder are analyzed according to the state of the bridge during the construction stage.The main contents are as follows:1?Combined with the field construction,the 3-dimensional temperature distribution and the stress and elevation of some sections of the steel box girder of the cable-stayed bridge were measured,and the temperature field and temperature effect of the separated steel box girder section under the daily radiation environment were obtained.According to the test results,the three-dimensional problem of the temperature distribution of the cable-stayed bridge is simplified as a two-dimensional problem.Using the numerical analysis method,the vertical and transverse temperature gradient formulas of the steel box girder section in the construction stage is fitted.The vertical temperature gradient is fitted in exponential form,and the transverse temperature gradient is fitted with 4 times polynomial.2?The finite element software Midas/Civil was used to establish the model of the main span of the cable-stayed bridge with hybrid girder before and after the closure.The stress and deformation of the girder and pylon under the temperature difference between the cable and the beam,the temperature difference between the pylon itself and the overall temperature difference was studied,as well as the change regulation of the cable force.Quantitatively describes the influence of the temperature difference between the components of the cable-stayed bridge on the structure.3?Based on the basic assumptions,an ANSYS solid model for the standard section of a steel box girder was established.The stress of steel box girder under self weight,transversetemperature distribution load,vertical temperature distribution load are obtained by loading the measured temperature distribution curve.The error between the calculated result and the measured value is small,which indicates that the model adopted in this paper is reasonable.In addition,it is found that the transverse temperature gradient aggravates the inhomogeneity of the temperature stress in the cross-section of the steel box girder,and its influence on the structure could not be ignored.4?Based on the ANSYS model,the distribution of shear lag in different longitudinal and transverse parts of steel box girder is studied.The results show that the shear lag coefficient is larger in the central of the top plate of the separated steel box girder,and there is a serious stress concentration at the place where the cable acts and the corners of the cross section,while the web has no obvious effect on the distribution of shear lag.