Steel structure, assembly jig frame and assembly process

The invention discloses a steel structure. The steel structure comprises a plurality of pre-bent outer arc pipe pieces and inner arc pipe pieces which can be spliced and connected into an inner and outer circular ring-shaped steel structure, wherein a group of vertical rib plates and transverse partition plates are fixedly connected between the inner and outer arc pipe pieces of the inner and outer circular ring-shaped steel structure; the transverse partition plates are arc-shaped plates arranged in the circumferential direction of the inner and outer arc pipe pieces, the outer edges of the arc-shaped plates are fixedly connected with the outer arc pipe pieces, the inner edges of the arc-shaped plates are fixedly connected with the inner arc pipe pieces, and a gap is reserved between every two adjacent arc-shaped plates; and the vertical rib plates are a group of rectangular plates arranged at equal intervals in the axis direction of the inner and outer arc pipe pieces, the outer side edges of the rectangula