Long-span X-shaped three-dimensional grid string structure system and construction method thereof

The invention discloses a long-span X-shaped three-dimensional grid string structure system and a construction method thereof. In the structure, two middle common horizontal steel beams are located at the upper end in a spaced mode, and upper main cross steel beams are symmetrically arranged on the two sides of each middle common horizontal steel beams in a tilted downwards mode; a plurality of upper main cross steel beams are arranged on one side of each middle common horizontal steel beam and located in the same tilted plane, wherein the upper ends of two X-shaped crossed upper main cross steel beams are connected with the end point of one middle common horizontal steel beam respectively, and the lower ends of the two X-shaped crossed upper main cross steel beams are connected with one of two supports respectively; the end points, on the same side, of the two middle common horizontal steel beams are connected through upper horizontal straining beams. By means of the long-span X-shaped three-dimensional grid