Installation in shallow Box Girders: Strand Tendons for Incrementally Launched Bridge at the Inzersdorf Traffic Intersection
The 1.7km long Inzersdorf traffic intersection on the South East Ring Road in Vienna includes the highly frequented connecting roads of the A 2 South motorway and the A 23 motorway with the Altmanndorfer and Triester roads. The intersection was built in the 1970’s and required rehabilitation due to the high traffic load. The project also includes the partial new construction of a hollow box girder bridge with 2 separate post-tensioned concrete superstructures.
The bridge is being built using the incremental launching method, which reduces environmental impact to a minimum. No false work is needed, so that additional road closures were not necessary.
The southern superstructure was built in 25 increments with an additional falsework section while the northern superstructure was built in 24 increments. The section length varied between 10.50m and 22.69m. There were no tendons in the webs of the box girder.
In order to be able to accommodate the external loads once the bridge was completed, additional tendons were aligned in the spans of the floor slab and in the supporting area of the roadway slab that were anchored in pilaster strips. During incremental launching, the 10m wide and up to 300t segments were pushed step by step over the pillars using a lift thrust device to make room for the next section in the launching area. With the last bridge segment, a total launching load of nearly 8,000t was reached.
The standard cross section of the hollow box girder was required to be very shallow representing a special challenge for posttensioning the additional tendons that had to be installed after the bridge was in its final position.
For tensioning the bridge, DSI supplied and installed Type SUSPA Bonded Strand Tendons with approximately 450 Type MA 6-12 Anchorages and approx. 445 Type MK 6-12 Couplers. Furthermore, DSI supplied 184 high-strength, short bar tendons, Types 32 WR and 36 WR that were used to connect the launching nose tightly to the first segment.