The ambitious freeway project involving the demolition of the old bridge over the Düte River and construction of a new one is progressing according to plan. After successful partial demolition, various reinforced concrete components of the first half of the new bridge are already in place. The PORR team carrying out the construction work has the project perfectly under control – not least thanks to efficient formwork solutions from Hünnebeck.
The replacement of the 301 m long A1 freeway bridge over the Düte River near Osnabrück is one of the most challenging current bridge construction projects in Germany. The starting point is the monolithicstructure of the four-lane bridge dating from 1968, which has to make room for a much wider new structure with six lanes. The single-piece bridge superstructure requires a special approach, which, expressed in simple terms, means cutting the bridge lengthwise down the center and removing one half of the bridge, while the remaining half, supported by ready-erected shoring, is currently used for traffic.
After around five months for demolition, the first phase of construction for the new bridge began in summer 2018. The new bridge is being built as a so-called composite steel structure. This means that a steel superstructure will be mounted on the new reinforced concrete supports and bearings once erected. On this the concrete bridge slab is then poured. The contractor is Porr GmbH & Co KGaA Infrastruktur Ingenieurbau. When it comes to the design of the formwork for this complex major construction project, the Porr team is relying on Hünnebeck’s formwork experts. They have developed and supplied the formwork solutions required for the construction of the bridge abutments, pier foundations, piers and crossbeams in close cooperation with the project managers.
The result is an efficient and cost-effective mix of standard and custom solutions that is precisely tailored to the special conditions of this demanding bridge construction project. For example, Manto large-frame formwork is being used to pour the pier foundations and abutments. Its great versatility and special load-bearing capacity (concrete pressure: 80 kN/m2) ensure rapid shuttering times and high efficiency (not only) for these components.
The pier formwork, on the other hand, is a custom formwork construction provided by Hünnebeck consisting of H20 girder formwork elements arranged in a ring. The required formwork diameters are 1.80 m and 2.40 m with element heights of up to 10.25 m. For the special geometry of the crossbeams, each of which rests on two bridge piers, Hünnebeck’s own special formwork construction department has produced a tailor-made special form with a vertical board structure. On the long sides, this special construction is supplemented by standard panels of Manto form- work on the outside.
The crossbeam formwork is supported by shoring from the new Hünnebeck ST 60 system, which has been particularly well received by contractors. The Hünnebeck formwork foreman supervising the construction site and on hand for advice was particularly pleased: “The ST 60 has truly been optimized for the construction site in all respects. Whether assembly, disassembly, transport or storage – our new shoring system for formwork construction is already meeting the requirements of the future.” For example, no part of this system, which conforms toboth DIN EN 12810 and DIN EN 12811, weighs more than 15 kg; in addition, there is safe assembly and disassembly at all times thanks to advance side protection and a Hünnebeck patented particularly ergonomic lining transfer process.
The system is characterized by high levels of simplicity and safety: The ST 60 modular system consists of only six basic parts. With just two frames, three tower widths can be pro- duced: 113 cm x 113 cm, 150 cm x 150 cm and 113 cm x 150 cm. Up to 240 kN load capacity per tower (60 kN per column) and the system’s compatibility with aluminum and steel girders as well as with wooden formwork girders (H 20 and R 24) ensure high load-bearing capacity and safe load discharge at typical application heights of between 3 m and 15 m. One of the most important features of the ST 60 tower is its special method of shifting the planks: The planks (load class 4) are easily and ergonomically moved to the next level with a special plank lifting device. Once the tower is fully assembled, it can be suspended from a crane with a four-leg sling as a single unit for easy transport on site.
The PORR construction site team is extremely satisfied with the formwork solutions provided by Hünnebeck: “Everything tells you that practitioners are at work here who know exactly what counts on the job site. Whatever the formwork – tailor-made custom solutions or off- the-shelf systems – safety and practicality are the top priorities.” This satisfaction also finds expression in the fact that the construction progress is on schedule: Traffic is expected to be routed over the first new half of the bridge by the beginning of 2020. The demolition of the remaining half of the bridge and the subsequent constructionof the new section can then begin. Once again, tried-and-tested Hünnebeck formwork solutions will be used.