Construction method adopting large-span gantry crane to hoist tie bar

The invention discloses a construction method adopting a large-span gantry crane to hoist a tie bar, comprising the steps of: excavating a foundation of a pile; hoisting and welding a frame of the gantry crane; placing stringers and beams of the frame and positioning the rail of the gantry crane; and assembling the gantry crane and hoisting the tie bar. The construction method has the main advantages that: the defects that during constructing with a full framing method, the stress of the frame cannot satisfy construction requirements, the foundation is difficult to process, and the construction cannot be performed at the part over a railway are overcome; the middle tie bar is 103 tons in weight, the hoisting height is at least 25 meters, the working radius of the crane is at least 35 meters, therefore the construction requirements cannot be satisfied by conventional methods, the installation of the tie bar above the railway cannot be implemented, furthermore the construction safety cannot be ensured; compared