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Raab Bridge in Gleisdorf

Photo: construction site situation; bridge, cranes, scaffolding, construction site signage, and trees; a river and houses in the background
Facts and Figures
Company PORR Bau Gmbh, Steel Construction department, PORR Bau GmbH, Styria branch
PrincipalProvince of Styria
LocationGleisdorf - Austria
Type Bridge building
Runtime12.2019 - 09.2020

A one-of-a-kind bridge construction.

The two-span rolled girder-in-concrete structure of the Raab Bridge in Gleisdorf, which had been built in 1927, no longer met present-day requirements. In June 2019, therefore, the Styrian provincial government commissioned PORR Styria with the construction of a new bridge across the river Raab.

Our team designed the new structure as a tied-arch bridge using precast construction methods without central piers and with a span of 29.2m. The Styrian provincial government had originally planned to have the arch built in in-situ concrete. However, our team of experts from the Styria branch and the Steel Construction department were able to convince the people in charge of the project of the advantages of the following unusual combination.

The two tie girders are made from steel, and the carriageway slab is a composite steel construction. The choice of superstructure made it possible to increase the flow cross-section of the Raab River below. Bored piles with a diameter of 90cm were used for the foundations. The materials were selected according to their respective strengths – precast concrete was used for the parts of the superstructure under compressive stress and steel was used for those under tensile stress.

Both the steel superstructure and the arch were delivered to the construction site in ready-to-assemble condition. In a pure steel structure, the arches and longitudinal girders would have been assembled in the factory beforehand in order to test them for dimensional accuracy. This was not possible for this structure. For this reason, we had to pay special attention to the connecting surfaces and tolerance compensation during installation. We designed retro-cast steel mounting parts to absorb the tolerances resulting from production and assembly-related inaccuracies and to transfer any occurring forces.

The Raab Bridge in Gleisdorf is the only bridge we know of where a precast concrete arch and a steel composite carriageway were combined in this way. Once again, PORR has impressively demonstrated how good in-house teamwork and constructive coordination between different departments can allow projects to be implemented in an exemplary, efficient manner and to the client’s complete satisfaction.