Design of Demolishing Scheme for a 3-Span Continuous Box Girder Bridge

For the demolishing construction of a 3-span continuous box girder bridge with span arrangement(18+26.4+18) m,a demolishing scheme was proposed and designed,i.e.,the main girder of the bridge was stabilized by the bailey truss and suspenders,the girder was cut into 3 sections by the diamond steel wire cutting method,the section of the girder over the central span was lifted away by the overhead launching gantry and shifted to an open ground where it was then broken into pieces.The side spans flanking the central span and the 2-m remaining sections of the central span were broken in situ on staging.To ensure the construction safety,the internal force and deformation of the structure in the construction process were analyzed by the finite element software.The results of the analysis indicated that the deflection of the bailey truss was greater than that of the main girder,which caused great tensile force in the suspenders at both sides of the truss and little tensile force in the suspenders in the middle.In that case,the suspenders were pre-tensioned before lifting and in the lifting process,the axial forces of the suspenders were adjusted.Presently,the demolishing of the bridge has been completed and the whole process of the demolishing is safe and controllable.