Study On Temperature Effect Of Long-Unit And Large-Span Highway-Railway Continuous Steel Truss Bridge

The continuous steel truss bridge has been widely used in the construction of high-speed railway Bridges because of its advantages such as strong span capacity,large stiffness and economizing bridge location.Because most of these Bridges are designed with more than double lines,the uneven sunshine temperature gradient is obvious due to the shielding of the wide deck deck to the structure itself.At the same time,due to the large size of this kind of bridge surface,the effect of uneven temperature field will have a great influence on the force and deformation of the bridge no matter in the construction stage or in the completion stage.This paper takes a continuous steel truss bridge for both railway and highway as the concrete object,systematically studies the effect of uniform temperature and temperature gradient on it.The main research contents and conclusions are as follows:(1)Summing up the survey results and combining with the design of the real bridge,the temperature field test scheme is formulated.The measured temperature distribution law along the transverse and vertical temperature gradient of the beam section is fitted,and the temperature field of the bridge construction stage and the bridge completion stage are obtained.The data analysis results show that the sun’s irradiation intensity,duration and the position of the rod are the main factors affecting the temperature variation of the rod.The shielding of the bridge deck has a significant effect on the temperature difference between the bridge and the bridge.(2)The finite element analysis method is used to analyze the stress and linear shape of the bridge in three construction stages: cantilever assembly,system transformation and closure.The effect of the ratio of uniform temperature and temperature gradient on different construction stages.The results show that the effect of temperature gradient on the local stress of the bridge is significant.Under the maximum cantilever condition,the effect of temperature gradient on the bridge alignment is the greatest.In the two stages after the system conversion and after the closure,the overall cooling effect is sensitive to the vertical displacement of the structure.The overall warming effect is sensitive to the longitudinal displacement of the bridge.(3)The finite element model of the bridge was established to study the mechanical performance of the bridge during operation,and the influence of uniform temperature action and temperature gradient action on the static performance of the bridge was compared and analyzed.The results show that the effect of temperature gradient on the stress of bridge is significant.For the lower chord of side span,the stress caused by temperature gradient increases by 8.0 % compared with the stress caused by the dead weight and design load only.The overall cooling effect is sensitive to the vertical displacements of the side span and middle span of the bridge.At the most unfavorable positions of the lower chord of the side span and the upper chord of the middle span,the vertical displacements caused by the overall cooling reach 2.7% and 9.0% of the vertical displacements caused by the design live load,respectively.