Simulation Analysis of Jacking-down of Girder in Incremental Launching Construction of Oblique Continuous Box Girder

To have an understanding of the structural force conditions of the oblique concrete continuous box girder bridge in the construction of incremental launching and jacking-down of the girder and to provide technical support for the construction,the Yingpan East Road Liuyang River Bridge in Changsha city was cited as an example,the process of jacking-down of the concrete box girder of the bridge was simulated and analyzed by the method of applying forced vertical displacement at the support nodal point,the jacking forces of the jacks and the stress of the girder were calculated,the calculations were compared to the measurements and the influences of the girder bottom height differences of the adjacent pier tops on the jacking forces and the stress were analyzed.The results of the simulation and analysis reveal that the top and bottom slabs of the box girder have been in compression all the time with the exception that only the stress of the girder at the jacking pier and adjacent piers changes relatively greatly.When the height differences of the girder bottom at the adjacent pier tops are within 25mm,the increment of the jacking forces of the jacking pier are within 5%and the cross section of the girder at the jacking pier remains compressive.In the jacking-down of the girder,the simulation calculations of the jacking forces and the stress of the girder are well agreeable with the measurements,showing that the simulation analysis herewith is correct and reliable.