Study On Monitoring And Control Technology Of Rotation Construction Of A T-shaped Rigid Frame Bridge

Under the government’s strategic plan for a country with strong transportation network,the national transportation network continues to be improved and expanded,which will inevitably require a large number of new bridges across existing bridges.To reduce the impact on the existing daily traffic capacity of the line,while ensuring the safety and affordability of new bridges.The swivel construction of the bridge can solve this problem.This paper takesa 62 m+70 m long-span and ultra-wide box girder T-shaped rigid frame bridge as the actual engineering project background.The cross section of the bridge is a single box with five chambers,and the bridge deck is set with two-way eight lanes with a width of 32 m.Due to the wide bridge deck,the long cantilever of the swivel,and the heavy mass of the swivel,the designed swivel mass is 18,500 tons.In this paper,the construction method has been optimized and improved to a certain extent.The original full-floor bracket is dropped at one time,and the full-floor bracket is constructed in sections,and the racks are dismantled in batches.Compared with the one-time dismantling,the batch dismantling reduces the bracket erection period by more than 50%,and because the bridge deck is wider and the bridge height is higher,the use of the full hall bracket is larger,and the full hall bracket is installed in batches,which can reduce the use More than40% of the stent usage.Therefore,discussing the reasonable disassembly sequence of the full-frame section construction,analyzing the influence of pre-stress tension on the full-frame bracket and reasonable division of construction sections can reduce the project cost and construction period.The swivel part of this bridge is a widening section at the large mileage,and the swivel structure has a long cantilever,and the overall unbalanced moment is large.Strict construction control is required during the swivel phase.In order to study the overall stability of the bridge at the turning stage,this paper calculates and analyzes the unbalanced moment of the T-frame bridge itself.According to the analysis data,the theoretical counterweight calculation of the T-frame bridge and the bridge weighing test are carried out.The longitudinal eccentricity of the bridge is 0.025 m,the unbalanced moment is 4583 k N · m,and the longitudinal and transverse spherical joint friction coefficient is 0.0264,which is the bridge structure’s Swivel stability provides a certain guarantee.Since the mass of the bridge swivel weighs 18,500 tons,the swivel angle is 72°.Therefore,the spherical hinge and the rotating system will be subjected to a great vertical load during the rotation.In this case,the analysis of the stress state of the spherical hinge under different construction conditions is extremely important.The analysis results show that the concrete at the edge of the steel spherical hinge is prone to stress concentration and tensile stress on the top of the upper turntable.After thickening the connection between the upper turntable and the double-limbed thin-walled pier by 2 m,the tensile stress is reduced from 3.57 MPa to 1.9 MPa under the most unfavorable load conditions,and the tensile stress is reduced by about 45%,which proves that Thick treatment helps to improve the stress performance of the upper turntable.