The Institute of Structural Engineering of the TU Wien has been working on a construction method with lightweight precast thin-walled con- crete bridge girder that would enable concrete to become an attractive alternative option to steel when it comes to the construction of bridges without formwork. The main idea consists of using precast elements in collaboration with in-situ concrete in order to create light- weight trough-shaped or box-sectioned bridge girders that can easily be handled during transport and mounting. The precast elements serve as permanent formwork for the subsequently added in-situ concrete and can therefore considerably reduce the use of formwork and false- work on the construction site. The focus point of the design with these precast elements is the calculation of the different construction phas- es. Designs of short span as well as large span bridges with trough-shaped and box-sectioned bridge girders respectively, will be discussed.