Cast-in-situ beam-making construction method of assembled support

Disclosed is a construction method of producing a beam in situ by pouring an assembly-style bracket, which is characterized in that a foundation is treated by cement compaction piles into a composite foundation; that buttresses in a support system adopt Bailey cranes and vertical load-bearing beams adopt military beams; that a box beam formwork is formed by combining such three major parts as a bottom mold, an external mold and an internal mold; wherein the bottom mold is formed by matching large pieces of flat steel templates; the external mold adopts a light welded steel structure, the internal mold adopts a screw mechanical contraction steel structure and is formed by matching the segments, and both the external mold and the internal mold can slip along a railway which is disposed on the military beam. The construction method has advantages that: 1. the load-bearing capacity of the composite foundation can reach up to 239KPa so as to meet the load-bearing requirement of the middle buttress; 2. the assembly-style bracket only costs about 3.7 million, the components thereof are standing parts so that installation is convenient. In addition, the moving of the external mold is beyond the restriction of box beam ages, as long as the intensity is satisfied, the external mold can be drilled with holes. The assembly-style bracket can be used as construction equipment such as a gantry, an erecting crane and a makeshift bridge after construction and can be reused repeatedly.