| The elevated bridge is the main structural form of high-speed railway that has reached nearly 30,000 km in China,and 70% of it is in the form of box girder viaduct.The Haqi high-speed rail viaducts account for more than 70% of the total,90% of which are 32 m single-chamber single-chamber simple-supported box girder.To ensure its 100-year design life,it is necessary to solve the construction of large-tonnage post-tensioned prestressed box girder and In the performance problem of high-speed train operation,it is necessary to carry out research on the key construction measures of 900 t post-tensioned prestressed box girder to solve the technical problems of construction,and carry out the bearing performance of box girder under different train running speeds to verify the reasonable design and construction technology.This paper mainly carried out the following work:Firstly,the key construction techniques of four 900 t post-tensioned prestressed box girder are discussed.Firstly,the method of drawing and forming holes by rubber rods solves the technical problem of the forming of the dense prestressed beam curve of the box girder,and effectively avoids the slurry leakage caused by the concrete vibrating pouring during the forming of the conventional plastic corrugated pipe and the metal corrugated pipe.The difficulty of beaming the dense prestressed beam is reduced,and the risk of uncompacted grouting in the prestressed tunnel is reduced.Secondly,a large box girder formwork system consisting of a fixed bottom mold,a hydraulic automatic shrinkage steel inner mold and an integral steel outer mold is formed.The internal formwork construction work including the hydraulic system and the running structure is quick and effective.The cross-sectional dimensions of the box girder and the construction quality of the structure.The third is to realize the integration operation of the 900 t box girder of the one-piece tire type beam-lifting machine,and adopt the idea of “four-point lifting and three-point balance” to achieve the coordination and unification of the falling beam and lifting beam process.The fourth is to complete the work of the girders according to the principle of balanced lifting,and the method of anti-rollover of the cantilever over-hole of the bridge-building machine is proposed.Secondly,the numerical simulation of box girder construction under different load conditions is carried out in a targeted manner.The box girder under the structure self-weight,the second-stage dead load and the pre-stress are calculated and analyzed by means of time division and segmentation.The stress distributionand the total deformation of the reverse arch and the construction stage caused by the prestress are obtained.Combined with the field load test of two cycles,the control section stress,bending moment and mid-span deflection are well matched with the simulation results,which verifies the rationality of the simulation analysis construction process.Finally,the performance analysis of 900 t post-tensioned prestressed box girder under different train speeds is completed.It is found that the box girder is affected by downward gravity and upward friction.The deformation of the prestressed beam box girder in the moving state of the train is obtained,and the vertical strain and the deflection of the beam are correlated with the train speed.The box for simulating the speed of different trains is simulated.The stress state of the beam is quantitatively analyzed for the positive correlation between the velocity and the stress and strain of the box girder.Through the performance analysis of the lower box girder of the train,it is verified that after the effective control of the box girder construction process,the 900 t post-tensioned prestressed box girder can meet the design requirements. |
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