The invention relates to a construction method for newly building an
arch bridge in situ of an old bridge. The construction method comprises the steps that arch foot foundations are newly built at the two ends of a main beam of the old bridge, and steel
pipe arch construction is conducted on the arch foot foundations; a plurality of slings are installed on the steel
pipe arch, supporting ropes are installed at the bottom of the old bridge girder section by section, and each supporting
rope section is connected with the corresponding sling; the old bridge girder is
cut and dismantled segment by segment with the old bridge
pier as the center, and the old bridge girder is transported to the set position segment by segment; and a new bridge girder is erected, and the new bridge girder is connected with the steel
pipe arch through the slings to form the newly-built
arch bridge. A sling on a new bridge steel pipe arch is used for lifting an old bridge girder, and the old bridge girder is symmetrically
cut and dismantled section by section with an old bridge
pier as the center, so that the risk that an old
bridge collapses due to unbalanced stress in the dismantling process is reduced, normal navigation in the dismantling and
building construction process is guaranteed, and the construction efficiency is improved. The technical problems that in the prior art, the construction period for dismantling and rebuilding a conventional old bridge is long, the old bridge is prone to collapse in the dismantling process, and navigation is interrupted are solved.