Doka quality for the next hundred years

An efficient way for traffic to cross the Aurach valley must continue to be available despite the upcoming construction activities. Therefore, a new supporting structure first will be built parallel to the existing bridge, onto which traffic will be temporarily diverted from the end of 2023, while the new bridge designed for significantly higher loads will be built.

The executing consortium HABAU/PORR is relying on Doka's know-how to ensure that the new Aurach bridge can act as a functional and reliable transport link across the Aurach valley for at least the next hundred years. The Doka technicians' many years of experience and the customised solutions in balanced cantilever construction are indispensable in the implementation of this major project.

For each of the bridge's five piers, 30 bored piles with a depth of up to more than 30 metres were needed. Austria's largest rotary drilling rig with an operating weight of 180 tonnes was used in 2022 to prepare the ground. Then, in autumn 2022, concrete was poured for the five foundations on which the piers, each weighing several tonnes, were moved into place and erected. Framed formwork Framax Xlife and Doka's MF240 climbing formwork were used to construct these piers, which are up to 40 metres high.

Concreting using the balanced cantilever method
After completion of the piers, the so-called hammerheads that serve as the respective starting points for the balanced cantilever construction method were concreted on top of them. The Doka cantilever forming travellers are now being used for precisely this procedure, which combines planning and cost reliability with an optimum construction sequence. The perfect coordination between the falsework and the formwork, the high safety standard and the optimised ergonomics ensured that construction progressed swiftly and safely. In this way the subsequent construction sections can be added in parallel to each of the freely projecting ends of the hammerheads.

"The challenge here is the short length of the hammerheads that make it impossible to fit the two cantilever forming travellers one after the other or side by side," explains Markus Stastny, Technical Manager at Doka Austria. His team came up with the so-called "fork solution" as an answer. "On the one hand, this allows the traveller to be placed inside each other in a space-saving way and on the other hand, as little conversion work as possible is required during the balanced cantilever construction planned with DokaCAD for Revit", says Stastny. Beginning in March 2023, the superstructure will be built symmetrically in 5-metre sections, starting from the hammerheads.

Rapid construction progress thanks to concrete monitoring system
To accommodate the tight construction schedule, Doka's Concremote concrete monitoring system is in use as part of the balanced cantilever construction. The sensors provide reliable data on concrete strength, enabling safe post-tensioning of the bridge tension cables. Due to the high demands of the construction site, a new reporting function was also implemented for the HABAU/PORR consortium, enabling detailed recording of the measured values in all concreting sections. This included significant time savings in documentation.

That was just the beginning
Once the first superstructure is completed and the carriageway is asphalted, at the end of 2023 all traffic will be diverted onto these sections in two lanes, so that the actual construction of the new Aurach Bridge can begin. First, the two old supporting structures including the carriageway and the associated piers will be removed. Subsequently, separate piers will be erected for each directional carriageway and the supporting structure including the carriageway in the direction of Vienna will be completed. Then the actual masterpiece, which requires millimetre work, will be completed: The supporting structure in the direction of Salzburg, with a weight of approx. 15,000 tonnes, will be moved from the bridge to the new piers by means of a transverse shifting procedure. After this, the temporary piers of the bridge will be removed.

Good to know
The new Aurach bridge will ensure a future-proof infrastructure according to the latest technology and standards. Almost all the material removed from the old and temporary substructures will be recycled: The concrete will be crushed, processed and reused as construction material. In addition, around 4,000 new trees will be planted to renature the construction site.