Concrete double-case subsection beam construction method

The invention discloses a construction method of a concrete double-box segment girder, more particularly relates to the construction of the bridge segment girder, comprising the following steps: 1) the segment girder is hoisted to position and an oil-jacked support is installed; 2) a wet seam bracket and an internal template as well as an external template are installed, and wet seam concrete is cast; 3) after the wet seam concrete reaches the requirement of design strength, the internal template and the external template are removed and F6 and F5 are stretched; 4) the thickness of the mat of the oil-jacked support of the midspan segment girder is reduced by 30mm, and other oil-jacked supports are unloaded according to the parabola of degree 4; 5) after F4 to F1 are stretched, the limitation of a bridge fabrication machine to the girder body is released; 6) steel strands B5 to B1 are stretched; 7) a diaphragm plate is cast and a transversal prestress bundle is stretched; and 8) the bridge fabrication machine