Research On Structural Behavior Of Continuous Steel Box Girder Bridge During Incremental Launching Construction

Incremental launching construction has the advantages of small construction space,no interruption of traffic,easy to cross the deep valley and so on.Walking push construction for continuous push construction and effectively avoid the "beam crawling" phenomenon,since the successful application of Hangzhou Jiubao Bridge has been rapid development and wide application.In view of some problems existing in the construction of the push,the main work and research are as follows:1)Summarize the existing top-loading methods from different angles,analyze the advantages and disadvantages of each method and the difference of force.The basic principle of the pushing force in the top-pushing construction is that the horizontal thrust is greater than the total frictional resistance.From the numerical analysis The formulas of horizontal thrust are given under different working methods and different factors(such as dynamic and static friction coefficient,slope slope of slope).2)According to the dynamic change characteristics of the top construction condition,the calculation model is established by using Midas/Civil,and the variation law of the structure stress state during the construction process is analyzed.The calculation shows that the steel box of the maximum stress of the beam is greater than the stress state in the bridge state;the vertical displacement of the steel box girder and the construction process and the structural arrangement have the periodic circulation rule.The displacement of the front beam of the guide beam is changed regularly from n1 pier to n-The displacement is gradually increased from 0(absolute value),to be guided beam to the n1 pier,the vertical displacement and basically returned to 0,and the tail due to the beam center of gravity forward and upturned in the new hoisting welding a box girder The post-uplifting steel box girder returns to the top of the platform under the action of the self-weight,and is continuously circulated along with the progress of the construction.The simulation results show that the multi-The reinforcement of the beam is effectively reduced by the support force of the larger supporting force bridge,which further improves the stress state of the beam.3)According to the constraints of engineering space and traffic conditions can not set the temporary pier,directly on the permanent pier on the top of the beam,the lower structure of the force of the system research;pointed out the level of force(braking force)distribution and piers and the calculation formula of the horizontal force distribution of the push process is deduced according to the principle of calculation and the horizontal force calculation of the flexible pier.The distribution of the horizontal force is calculated according to the stiffness and friction coefficient of different pier,and the horizontal force distribution in different cases is found And the correction coefficient of the stiffness of the piers is calculated and the value of the stiffness correction coefficient of the bridge pier under different conditions is verified and the reliability is analyzed.4)The main reasons for the lateral migration are analyzed from the aspects of equipment precision,technical status and statistics.The differences of the correction modes are described by the wedge block correction as the main model and the similarity And the use of Midas / Civil to establish the piers model to simulate the longitudinal displacement and lateral displacement of the combination of a variety of combinations,the analysis shows that the lateral displacement under the action of the pier will be eccentric force state,when the eccentricity exceeds a certain limit when the pier The stress is nonlinearly increased,the lateral displacement value is strictly controlled during construction.The variation of the stress at the bottom and the diagonal web after the displacement of the bearing and the position of the bearing is found.When the support force is 100 kN,And the stress of the bottom plate and the diagonal web are increased by about 49.23% and 62.50% respectively.It can be seen that the lateral deflection of the beam will aggravate the local stress concentration.The effect of the bearing reaction caused by uneven distribution of the situation,the stress increase will be greater;therefore,the lateral deflection of the beam is not conducive to structural force,The construction needs of timely correction,to ensure structural safety.