Analysis And Application Of Main Beam Construction Control Of Long-span Composite Beam Cable-stayed Bridge

The steel-concrete composite beam cable-stayed bridge has become the main type of long-span bridge because of its light structure,strong span capacity,beautiful appearance and strong economy.In recent years,steel-concrete composite girder bridges have made great breakthroughs in theoretical research and engineering practice.Taking Chibi Yangtze River Highway Bridge,the world’s largest steel-concrete composite girder bridge with main span,as the engineering background,this paper makes a detailed study on the key technology of construction control of long-span composite girder bridge based on the construction control and related calculation theory of composite girder cable-stayed bridge.The main research work of this paper can be divided into the following aspects:(1)The development of cable-stayed bridges and steel-concrete composite girder cable-stayed bridges is summarized;The development of section forms of steel-concrete composite beams and the current research status of composite beams are described.The geometric nonlinear effect of cable-stayed bridge is theoretically deduced;The material nonlinearity caused by the shrinkage and creep of concrete bridge deck and the calculation method of composite beam section are analyzed.(2)According to the structural characteristics of steel-concrete composite beam,the calculation principle of conversion section and internal force calculation method are expounded,and the calculation theory of double-layer beam element simulating composite beam is derived.According to the standard section of the main beam of Chibi Yangtze River Highway Bridge,the simply supported and cantilever structures are established,and the double-layer beam element model and the conversion element model are calculated and compared.The relevant calculation results show that the difference between the internal force and stress calculation results of the double-layer beam element model and the calculation results of the conversion element model is small.When establishing the double-layer beam element model,the element division length and load section are important factors to determine the calculation accuracy.When the load is applied to the steel beam element,the calculation error is smaller.When the influence of 30-year concrete creep on the calculation results is included in the structure,the calculation results in the two calculation models are highly consistent.(3)In view of the staggered holes between the steel cross beam and the splice plate caused by the torsion of the steel main beam during the cantilever assembly construction control of the main beam of Chibi Yangtze River Highway Bridge,which makes it difficult to install the steel cross beam normally,the mechanical model is simplified according to the engineering practice,and the finite element software is used for simulation modeling and analysis,and the specific measures for on-site torsion correction are put forward.(4)Through the analysis of the construction process of the special section of the main beam of Chibi Yangtze River Highway Bridge,the whole construction process and closure sensitivity of the main beam are analyzed.The results show that the cantilever erection of the main beam has been in a safe and controllable state from passing through the auxiliary pier to the completion of the auxiliary pier,indicating that the installation of temporary pier jacking device can ensure the elimination of unbalanced load in the thickened section of the side span concrete deck,and also ensure the smooth erection of the main beam to the auxiliary pier.Through the analysis of the whole construction process of the main beam,it can be concluded that the stresses of the bridge deck and the steel main beam meet the design and specification requirements,indicating that the construction process of the main beam has been in a safe and controllable state.For the relative height difference of the closure,it is more effective to eliminate it by adjusting the vertical load than by adjusting the cable,and the horizontal(longitudinal)error can be eliminated by horizontal(longitudinal)tension.