Launching Girder is also known as Launching Gantry. A launching girder is in general a design-and-built machine used in precast post-tensioned bridge construction. It consists of lifting devices and a supporting structure for lifting precast beams and precast bridge segments in position for assembling.

Launching girder (LG) is equipment used in metro rail construction to lift and assemble prefabricated concrete segments, which are then joined to create the span of the viaduct.

Firstly, good stability of hoisting of the girder: two trolleys cooperate with each other in three-dimensional motion with the girder, meeting the requirements of the girder erection.