Variable box variable cross section continuous rigid frame aqueduct single-box single-chamber box girder and design method thereof

The invention provides a variable box variable cross section continuous rigid frame aqueduct single-box single-chamber box girder and a design method thereof. According to the method, in the process of casting the variable cross section single-box single-chamber box girder, with the gradual increase of the cross section, an arched curve is formed at the lower edge of the bottom plate of the single-box single-chamber box girder; the change rules the same as that those of the curve of the lower edge are adopted for the upper edge of the bottom plate, so that the bottom plate forms an arched curve whole with identical thickness; gradual change space is formed between the upper edge of the bottom plate and box inside water body space of concrete of the single-box single-chamber box girder; the gradual change space is filled with cushion layers so that the upper surface of the gradual change space is smooth. According to the invention, the problems caused by sudden increase of the thickness of the bottom plate of a conventional box girder are solved, the prestressing effect of longitudinal prestressed rebars is improved, and the problem in the arrangement of box girder bottom plate longitudinal prestressed steel bundle anchoring toothed plates is solved, and the additional temperature gradient effect of the bottom plate of the single-box single-chamber box girder is reduced; the self-weight of a midspan area of a continuous rigid frame aqueduct is reduced, the overall deformation of the structure is improved, and the economical efficiency is great.