Cable-stayed bridge with mixed highway and railway arrangement

The invention provides a highway-railway mixed cable-stayed bridge which comprises an upper-layer bridge deck structure, a lower-layer bridge deck structure, two main trusses and a stay cable structure, the two main trusses are arranged at intervals in the transverse bridge direction, the upper-layer bridge deck structure comprises an upper cross beam and an upper-layer highway bridge deck, and the upper cross beam comprises a cross beam body and a cross beam cantilever arm; the lower-layer bridge deck structure comprises a steel box girder, a lower-layer railway bridge deck slab and a lower-layer highway bridge deck slab, the steel box girder comprises a box girder main body and a box girder cantilever arm, the lower-layer railway bridge deck slab and the lower-layer highway bridge deck slab are laid on the box girder main body and the box girder cantilever arm respectively, the stay cable structure adopts a harp-shaped cable surface, and the lower end of the stay cable structure is fixed to the lower layer