The TU Dresden is decisively involved in the development of a sustainable and transparent glazed roof structure. The designed transparent space grid structure is based on a conventional steel space grid, in which all steel members of the compression layer are replaced by glass panes.

In 2007 the first realisation project using this new concept was launched and finished this year. With a dimension of 13.5 m x 21 m and an arch rise of 3.50 m it covers the courtyard of one of the Berlin palaces. The roof consists of double layer arches with field sizes of 1.80 m x 1.26 m. The lower layer consists of steel members with restraint vertical posts. The upper layer consist of IGU glazing, hinged connected at knots on top of the posts. The load bearing glazing in the IGU permanently transfers in-plane compression forces.

The design process was attended with extensive testing to obtain an individual approval. This contribution describes the testing for the individual approval as well as the design and assembling process of this unique roof structure.

For individual approval test at single panes and at the full-scale arch of 13.5 m span are demanded by the building authorities. Plastics for the in-plane load application into the glass edge and their creeping behavior was investigated in first tests. The stability behaviour against glass pane buckling was tested at relevant load combinations and the post breakage robustness and the walk-on ability of the overhead glazing ensured by suitable test. Load bearing tests with a total load of 13 tons were conducted on one 13.5 m arch and finished the test series.

The design process mainly was dominated by finding an optimal structural model causing minimal forces in the glazing and designing the knot as crucial element of the structure with multifunctional features.

After successful finishing the design and testing of the structure all single arches were prefabricated and transported to the site. In the minimum of four days all elements were put on its supports and connected together before starting the finishing work at the roof. The palace is going to be re-opened in November 2009.

The firstly realised roof structure on the basis of transparent space grids, in this case the structure geometry half-Vierendeel, demonstrated the potential of the structures. With a dimension of 21 m x
13.5 m the roof size is comparable to many inner courtyards at historical building ensembles in
Germany.