To improve the traffic situation in Tuttlingen, the merger of the two federal roads B 311 and B 14 was planned to improve the nationwide road network and to create a highly productive traffic situation in this area.
In the course of this merger of the two federal roads, the new construction of a two-span bridge over the River Donau in Tuttlingen was necessary. The bridge beam consists of a prestressed and haunched T-beam cross section. The height of the cross section measures 1,5 m in the midspan and increases up to 2,0 m above the middle pillars. The bridge beam is built with the help of a falsework in only one construction stage.
On basis of a specific proposal, for the first time in Germany in the field of new bridge construction, the application of internal prestressing of tendons with 31 strands (of St 1570/1770, with a cross section of 4,650 mm² per tendon and an admissible prestressing force of 5,929 kN according to the approval Z-13.1-114) was realized. 12 tendons were installed in the cross section of the bridge with a length of about 62 m.
In comparison to “standard” implementations, prestressing tendons of only 19 or 22 strands were used. The advantage of the tendons with 31 strands is the reduced required space in the cross section. Therefore the required prestressing load is concentrated and applied selectively in the beam bridge. The small amount of prestressing tendons creates a better situation for the placing of concrete in the bridge beam.
The strands of the tendons were placed with the help of a hydraulic sliding device in the already installed ducts HR 115/122.
The prestressing force was applied in three steps of 30%, 70% and 100% of the nominal loading of 6,500 kN by means of a hydraulic press. The falsework could be discharged after the application 70% of the prestressing force. Afterwards all ducts of the tendons were filled with special grouting mortar with low shrink characteristics to realize the corrosion protection of the prestressing steel and to create the subsequent bond of the prestressing force to surrounding concrete structure.
Awarding Authority: Regierungspräsidium Freiburg
Client: Bilfinger Regiobau GmbH
Design: Konstruktionsgruppe Bauen, Konstanz
Please note that this project was realized at a time when the relevant project company belonged to the group of companies of Bilfinger SE and not to the Implenia group. The company was transferred to the Implenia group in 2015 only. The Bilfinger group and the Implenia group are two different group of companies, not being related and acting independently.