Construction method of lower cross beam of main tower of highway-railway dual-purpose and river-crossing A-type cable-stayed bridge

The present invention provides a construction method of lower cross beam of main tower of highway-railway dual-purpose and river-crossing A-type cable-stayed bridge, 5 which comprises: carrying out bearing platform construction at a preset position; erecting a lower cross beam bracket after completing bearing platform construction, carrying out construction of second pre-pouring sections of the lower cross beam, carrying out construction of the first pre-pouring section after completing construction of the second pre-pouring sections, and in a process of construction of the first 10 pre-pouring section, synchronously and continuously constructing middle tower column part upwards, when completing concrete pouring of the first pre-pouring section and the second pre-pouring sections, continuously constructing the middle tower column upwards to a corresponding position of a first cross bracing, binding reinforcing bars and concrete pouring of closure sections of the first pre-pouring 15 section and the second pre-pouring sections, and carrying out pre-stress construction after installing a second cross bracing, and arranging built-in fittings on the bearing platform to connect and fix a steel pipe strut so as to ensure stability of the steel pipe strut to the lower cross beam support, and the lower cross beam is constructed by adopting a method of segmented pouring to ensure construction quality of the main 20 tower, and the tower column and the lower cross beam are constructed asynchronously, which improves the construction efficiency on the premise of ensuring the quality.