Studies on geometric control mechanism of constructional process of cantilever casting for large-span continuous box-girder bridge

Considering the general background of engineering project of Wuzhong Yellow River Highway Bridge, which belongs to large-span continuous girder bridge, some investigations of geometric control in the process of actual cantilever construction are discussed in this paper. Based on different theories of geometric control, the method of self adaptive control has been adopted, by which such main influences as pre-cambers, elevations and deformation of guyed travelers on the structure of pre-stress large-span continuous girder bridge are analyzed and the formulae of initialize heights of girders are deduced. Then, according to the demands of design and construction for the bridge, a geometrical FEM model with spatial nonlinearity is established and its construction process has been simulated so that some key parameters of geometric control would have been determined. For examples, the initial curves of pre-camber for different span are obtained, and pre-elevations are done in which a long-term course of shrinkage and creep influence of concrete on the structure and other faults in other large-span bridges are considered. Finally, the objective curves are obtained on the basis of pre-camber curves. The measured data from three stages of every segment of construction are all processed, in which the data of elevations of No. 10 pier including theoretical simulation and measurement in site while their pre stress tension is finished are compared with each other and very good agreement is given between them. The results demonstrate the theoretical simulation and related program are reliable. All these investigations not only provide a basis for the bridge of linear control, but also a reference about geometric control for construction of the other similar large-span bridge.