Stiffening load carrying surface structures with ribs or "stringers" (i.e. adding bifurcations to the cross section) is common practice in light weight design. Stringer sheets made of metal for instance are being used in the aerospace and automotive industry as well as in architecture. Advantages of this type of design include the possibility to shape and position stiffener ribs according to specific loading scenarios and to combine this approach with complexly curved surfaces. However, it is exactly these properties that pose challenges to the manufacture of such load carrying structures especially if steel is used as a material. A differential design approach (i.e. to create and form sheets and stringers separately and join them afterwards) results in unacceptably high productions cost especially during assembly. Integral design approaches on the other hand such as casting pose significant restrains on the freedom of design and material choices. Finally, cutting stringer sheet structures out of solid blocks (as used in some aerospace applications) leads to extremely poor material usage, long production times and excessive tool wear per part. As an alternative the joining of flat sheets and preformed stringers in order to create an intermediate preform evades these challenges entirely by separating the bifurcation of the cross section from a subsequent forming operation. In preliminary work a process chain of laser-welding and sheet metal hydroforming has proven to be particularly effective in producing multi curved stringer sheet structures made of steel. Both processes are well established in the industry and suitable for mass production. The dissertation at hand contributes to the further development of this process chain by analyzing its current limitations in terms of producible shapes and proposing strategies to avoid or extend them. The results include a detailed description of characteristical failure modes such as wrinkling of the stringers, cracking of the sheet near the stringer ends, positioning errors of the stingers on the finished part and unfamiliar springback phenomena. In order to master these challenges the thesis presents a detailed discussion of possible modeling strategies for the finite element analysis of stringer sheet forming as well as some analytical and numerical approaches to an adapted process control and some general design guidelines for stringer sheet parts with special provision to manufacturability.