Construction Technology On Multiple Points Curve Successively Incremeantal Launching Method

Taipinggou Major Bridge lies in Gansu Province. The length is 358.8m and the radius of horizontal curve is 1 380.965m. It is the longest span curved box-girder with the successive launching method. Aiming at the trait of construction, the box girder's prefabrication adopted integral curved formwork and the erection adopted single line multiple points curve successive launching method. With the method, the box girder's unity and the appearance are guaranteed. The speed is fast and the method is safety. The outer formwork of the girder adapted whole slipping structure, the inner formwork adopted the combination of whole truss support and partially removable structure. The design is in favor of construction and very safe. It decreases the self-weight of the slipway and the height of falling girder with the cast steel replacing the armor plate. The device of correcting error system, which uses the normal finish machining steel boxes form cooperating with normal machine jacks, increases the safety of construction. Substituting the single point push at the bottom of the girder for the double points makes the working procedure more simplified.Technical measures:(1) The foundation of the girder fabrication field bed adopted pile foundation. The outer rail adopted spread shallow foundation. With the treatment, good effect has been acquired and the requirement of construction can be met.(2) Building a temporary pier between 0# abutment and 1# pier as the transition pier when building up guide girder and pushing the box girder.(3) Adopting the integral slipping outer form panel and monolithic truss for inner form panel increased the panel rigidity, assured the girder appearance.(4) During successive launching construction, setting a ZLD100 level jack at the top of every pier, the girder drag journey was controlled through center control bed. Setting an urgency button at each observational point, when the girder's moving state was in unexpected condition it can be changed. The girder was placed on the slipway in the process of successive launching. In order to decrease the friction force, a polyfluortetraethylene sliding plate was set. Every pier has a correcting error system, which was made of jack piston and 30t screw jack and correct error seat. It can regulate the girder's moving direction in time when the girder deviated from the vertical axis within 5mm and consequently made the correcting error apparatus take a dual effect both correcting error and limiting position.Key Technologies:(1) The treatment method of the foundation of girder fabrication field bed;(2) The design of the temporary pier;(3) The design of the form panel of box girder;(4) The setting of the jack;(5) The curved girder's correcting an error in the process of successive launching.