Overall Translation Techniques of Multi-Span Prestressed Concrete Continuous Girders
The bridge crossing the abandoned Yellow River channel in Suqian is a continuous girder bridge with spans of 22.2m,3×30 m,and 22.5 m.The superstructure consists of four separated decks,where the outer two decks carry pedestrians and cyclists,and the central two decks accommodate vehicles.Located in an ecological reserve,the bridge has sound girders after decades of service.To meet the requirements of rapid reconstruction of the Yingbin Avenue without traffic closure,each of the original vehicle deck was integrally translated 3.25 m outwards after traffic diversion,leaving space for the planned viaduct.Considering the hydraulic conditions,a cofferdam consisting of steel sheet piles and water-flowing steel tubes was built outside each pedestrians/cyclists deck to assist the widening of piers in dry environment.During reconstruction,the jacks and pedometers were selected and distributed in accordance with the jack-up loads at the bearings underneath each vehicle deck and the space below girder soffit.Numerical calculation was carried out to determine the control indexes of vertical and transverse displacement deviations at supports during the jack-up and translation of girders.A PLC hydraulic synchronous control system was employed to control the alternate working of the pedometers and jacks,to ensure the accuracy of integral jack-up and translation of the deck and control the abrupt stress change.Once the deck was translated into the design position,the pedometers and jacks were demolished,and the pad stones,bearings and stoppers were moved to the original locations.
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