The Research On Construction Technology Of Long Span High And Low Pylon Cable Stayed Bridge

Based on the Yongjiang Cable-stayed Bridge Project,this thesis is divided into the following four parts:(1)Shoal bare rock area cofferdam construction technique in Inverted V-shaped type cable stayed bridge;(2)Temperature control technique of the mass concrete in Inverted V-shaped type cable stayed bridge;(3)Inverted V-shaped type cable stayed bridge main beam construction technique;(4)Inverted V-shaped type cable stayed bridge mid span closure technique.According to the design of Yongjiang cable stayed bridge,such as double inverted V-shaped type cable planes,asymmetric bridge span structure,long segment cantilever with wide in width cast in place girder,complex of the combined vertical curve,the real hydrological and meteorological circumtance in the procession of the construction,and so on,having a through comparative analysis between the theoretical analysis and the actual working conditions,successfully solved the technical and traffic organization problems in the construction of the long span inverted V-shaped type cable stayed bridge under the deep water bare rock conditions.The work efficiency was greatly improved,the construction safety and the construction quality were ensured,the best shape of the main beam after the closure and the desired cable force of cable stayed bridge are obained.This can give other similar projects an useful reference.The main contents and results are as follows:(1)9# pier foundation pit employ shallow fastener steel pipe pile cofferdam scheme.In the project construction process,adpot mechanized construction,simplifying construction,and convenient to installation,the fenced area is safe and reliable,free from quality and safety accidents,good social benefits can be achived.(2)During the construction of mass concrete pile cap in summer,the field temperature is simulated by the model,then obtain the optimization scheme and the temperature cooling down monitoring scheme for the concrete construction.After the theoretical analysis,found some problems in the technique measures optimizing,so another theoretical analysis was proposed.In the construction process,the experimental data testified the theoretical analysis was basically correct,after inspection,there are no construction temperature cracks,so the method and prevention measures which we adopted are effective.(3)In the construction procession,the structure of the hanging basket walking system was optimized,employed the walking system composed of the top truss walking facilities,and hanging basket retral hang-up walking facilities,instead of the traditional "C" shaped hook walking system,effectively solved the overlap problems between the "C" shaped hook walking system and the " Inverted V-shaped" cables on the main girder,as well as walking problems.Finally,the hanging basket can be pushed forward without cables restriction,and the construction technique is simple,convenient construction,safety,reduce the risks of construction,A patent technique was achived based on the core technology research.(4)Empoyed auxiliary hanging fore cable on the base of traditional C type hanging baskest,to adjust the elevation of the templates,thus the level of basket templates can be hochpraezis,the working procedure was simple,and the working procession can achieve synchronization,parallel operation with hanging cable,and steel,prestressed beam installation process,effectively shorten the casting cycle time of the cantilever beam section,greatly improved the cantilever casting construction procedure,saved project managementcosts.The measures of the adjustment elevation of templates in the initial cable tension procession compared to the conventional "C" type hanging basket,the tension time of the cable force was increased to three times,can be controlled accurately,which is good to the control of the cable force.(5)The concrete of the main beam is of 31.6m in width,standard section is 8m in length.Due to the times tension,the time of the standard block cast in place isneeded at least 12 hours,the initial setting time of main gird C55 concrete is needed at least 14 hours,the main gird concrete should maintain in the state of plastic flow,thus can avoiding tension cracks arise in the joint section due to a fast concrete initial set.(6)Employ the concrete spreader in the construction of the cantilever cast in place concrete of the main girder,which not only effectively controled the imbalance between the two ends of the cantilever and the two sides of the same side,but also focused on the design permission,to reduce the potential risk of lateral torsional risk,and other uncontrollable linear construction,so that the elevation of cantilever cast in place beam was in a controllable state and can be adjusted in advance;And this can make the concrete pouring more uniform,avoided the traditional unevenly spreading by concrete pump pipe machnine,to take the wrong steps such like employing vibrating spear to spreader concrete,effectively reduced the workload of workers and labor intensity,drastically reduced the construction cost and safety risk of cantilever cast in place beam,(7)During the curing time of the concrete box,because the inner chamber is easy to be closed,employ a humidifier to ensure the concrete humidity in the box,so as to ensure the strength quality of the concrete and eliminate the hidden defective of quality.