Construction method for closure section of external stiff framework of cast-in-place box girder

The invention relates to a construction method for a closure section of an external stiff framework of a cast-in-place box girder. The construction method comprises the following steps: mounting a side span pier column bracket bracket; constructing a side span cast-in-place section; mounting a folding section hanging basket construction hanging bracket; mounting a stiff skeleton; and a closure section formwork system is installed and poured. The method has the beneficial effects that the stiff framework locks the box girders on the two sides of the closure section before closure section concrete is poured, and the closure section concrete is effectively prevented from cracking before prestress is applied; the error between the on-site displacement and the concrete pouring amount is effectively controlled through the treatment of the sub-bins and sub-valves; a side span cast-in-place section formwork support is erected through the corbel bracket; the construction speed is high, the structural stability is high