Pushing method and device for middle span of large-span high-bridge-pier prestressed concrete box girder continuous rigid-frame bridge

The invention discloses a pushing method and device for the middle span of a large-span high-bridge-pier prestressed concrete box girder continuous rigid-frame bridge. The pushing device comprises combined I-shaped steel girders, base plates, welded steel plates, combined H-shaped steel girders, jacks and stiff frameworks. Each combined I-shaped steel girder is formed by welding two I-shaped steel girder bodies side by side. Each combined H-shaped steel girder is formed by welding two H-shaped steel girder bodies side by side. The combined I-shaped steel girders are vertically buried at the two ends of a box girder, and the burial depth is half the length of a web. The combined I-shaped steel girders are welded to web reinforcement meshes of the box girder. The reinforcement meshes on the two sides of a top plate of the box girder and the two sides of a reinforcement mesh in a bottom plate are welded to one end of the stiff frameworks in the longitudinal direction of the bridge, and the opposite stiff framewo