Construction method for ultrahigh combined support for bridge side span cast-in-situ section

The invention provides a construction method for an ultrahigh combined support for a bridge side span cast-in-situ section. The combined support comprises a beam column type support and two cantilever brackets, wherein upright posts of the beam column type support are fixedly connected with a bridge transition pier body through connecting rods; and the two cantilever brackets are fixed on the bridge transition pier body; bearing beams are arranged on the upright posts of the beam column type support and the cantilever brackets, and longitudinal beams are arranged on the bearing beams. The beam column type support is organically combined with the cantilever brackets, so that the combined support is strong in bearing capacity and wide in using height range and is suitable for T-shaped steel structures and cantilever beam side span cast-in-situ sections which are high in terrain clearance and are in complex geological conditions and severe climate environments.