Research On Incremental Launching Technology Of Steel Box Girder Of Curved Cable-Stayed Bridge

With the continuous expansion of the city scale and the increase of traffic volume,more and more cities need to build curved bridges due to the limitation of topography and environment.The incremental launching technology is widely used because of its high efficiency.There is less research on the stress analysis of the incremental launching of curved steel box girder,so it is necessary to study the internal force and deformation.Taking the double-box and multi-chamber variable-section continuous steel box jacking construction of the Lanzhou Chaijiaxia Yellow River Bridge as the engineering background,the concrete application of the steel box girder jacking construction technology for curved cable-stayed bridges is described.The construction of steel box girder and temporary structure,and the difficulties in the process of pushing are studied.Based on the beam lattice method and the principle of concentric circles,combined with the bridge alignment,the distance between temporary pier,the pushing distance,and the weight of the main beam,the finite element analysis software Midas civil was used to push the structure on the north and south sides into eight and five different working conditions.The law of internal force changes of the structure is obtained,and the most unfavorable temporary pier is determined to be L6 and L13.During construction,attention should be paid to the force change of the pier,and abnormal conditions should be monitored in time.Based on the simulation results and construction safety reserves,2 × 500 t jacking jack was selected for jacking construction.The calculation results of the support reaction force of the guide beam show that the 50 t jack is used under the inner and outer steel guide beams,and the temporary pier can be smoothly passed through multiple lifting and support pads.Two working conditions with large deflection of the guide beam are selected:North Bank pushing condition N2,South shore pushing condition S5,and the pushingreinforcement is performed according to 4m each time to study the stability of the variable cross-section I-shaped steel guide beam in the pushing construction.Combined with the simulation results of push-encryption,the overall and local stability of the guide beam,the transverse connection system,the connection between the main beam and the guide beam are analyzed.The results show that the overall stability of the guide beam on the north and south shores meets the requirements,and the root section of the guide beam is stable.It meets the requirements,and the central and end sections have sufficient safety reserves to meet the construction requirements.By analyzing the internal force,deformation and stability of the steel box girder and the guide beam during the pushing process,it is concluded that the steel box girder and the guide beam of this project meet the requirements and the temporary pier distribution is reasonable.The new jacking equipment used in the construction process is easy to operate,has good synchronization and stability,and has strong applicability.By increasing the contact area of the jacking equipment,temporary auxiliary equipment and the steel box girder,the stress concentration phenomenon is effectively reduced.The successful application of the two-way multi-point pushing technology in the steel box girder jacking construction of curved cable-stayed bridges has solved the technical problems of the complex plane linear steel box girder jacking construction and has certain practical significance.