Research On Jacking-Up Technique And Pier Replacement Of City Viaduct

The hydraulic jacking technology was first applied to the erection and movement of railway bridges.However,with the development of highway construction and jacking technology,it has been applied more and more widely in highway bridges,especially in the reconstruction of old bridge,the movement of large-scale structures,foundation dragging and other projects.Taking the project of jacking-up of beam and pier replacement in Quanfu Flyover in Beiyuan Avenue as the research object,the application of hydraulic jacking technology in bridge reconstruction is introduced in this paper,from the aspects of structural theory calculation,design of lifting scheme and construction scheme,checking calculation of support system and counter force system.Firstly,a four-span bridge model is established in Midas finite element software.Based on the analysis of the influence on stress and deflection of the bridge in single pier jacking scheme the maximum jacking up of the single pier is determined to be 20 mm.Single pier jacking scheme and double pier jacking scheme are compared from the aspects of structural force and engineering cost,it approved that single pier jacking scheme(92# pier jacking up 10cm)needs less lifting equipment,and in which the internal force of beam is no dramatic changed,so it is selected as optimal lifting scheme in this paper.Secondly,the general construction plan for pier replacement project is design in in five aspects: design of counterforce foundation and support system,design of distributive girder and jacking control system,replacement of bearings and old piers,design and construction of new piers and design of monitoring program.Nine 609mm×16mm steel pipes are design as support for superstructure,and distributive girder is made of double-segment welding of 488 H steel to avoid excessive stress in the upper structure during the lifting process.Finally,the jacking construction scheme is checked from three aspects: the bearing capacity of the single pile in counterforce foundation,the strength,rigidity and stability of the steel supporting structure,and the stress calculation of the distributive girder.The checking results showed that the jacking scheme can meet the requirements of jacking-up of beam and ensure the safety and stability of the structure during the bridge jacking and pier replacement.