Safety for waterborne transport

Repair of weir pillars with special constructions and BIM planning

Data & Facts

  • Project
    • Main weir in Viereth, Germany
  • Principal
    • Wasserstraßen-Neubauamt
    • Aschaffenburg, Germany
  • Contractor
    • Johann Bunte Bauunternehmung, Office for Civil and Hydraulic Engineering and Bridge Construction
  • MEVA systems
    • Mammut 350 wall formwork
    • STB support frame
    • MEP shoring tower
    • KLK climbing system
    • BIM planning / special construction
  • Engineering and support
    • MEVA Schalungs-Systeme GmbH, Haiterbach, Germany

Repair of weir pillars with special constructions and BIM planning

The oldest weir system on the River Main is ­under repair and being made fit for the next 80 years. To avoid hindering waterborne transport and the release of floodwater, the two existing weir fields are being successively modernised – with wall formwork, safety and climbing systems, special constructions and BIM planning from MEVA.

The 527 km long Main is important for inland navigation in the south of Germany. The gradient of the river from its source in the Franconian town of Kulmbach to the point where it flows into the Rhine in Mainz is regulated by 34 barrages with 100 movable weir gates. The oldest system in Viereth near Bamberg has been in operation since 1925. In recent years an increasing amount of damage and wear has been discovered in the roller gates and the toothed tracks. Thus, work now needs to be carried out on the old weir system. The work required for the extensive overhaul commissioned by Wasserstraßen-Neubauamt Aschaffenburg (the local waterway construction authority) has been underway since 2014. In 2021 the weir will be ready for the next operating period of 80 to 100 years.

Movement in complex guides
For the formwork tasks on the central elements of the weir, the three weir pillars, the construction company Johann Bunte Bauunternehmung is relying on formwork systems, special constructions and BIM planning from MEVA. The weir must be capable of regulating the water levels for shipping on the Upper Main during the entire construction period and at the same time be available to release floodwater without restrictions. It is thus only possible to work from May to October when drainage requirements are low, and only on one of the two adjacent, 30 m wide weir fields at any one point of time. The huge weir gates with their fish-belly flap gates dam the water up to a height of 6.0 m. The two gates are mounted in two outer weir pillars and one central pillar. The weir gates are moved hydraulically in semicircular guides in the weir pillars and anchored in robust shafts. The pillars need to be modified to suit the new gate geometry. Pouring this guide geometry and integrating the swivel mountings into the weir pillars are huge challenges and require specially designed wooden panels. This is where BIM planning comes into play: A 3D model was created on the basis of 2D plans which facilitated the construction of the wooden panels, the planning and communications with the customer.

No time to lose
The first task was to drain the construction pit, pour the basis and fill it with gravel. In April 2019 the old weir roller and weir bridge were lifted out using a 500-ton mobile crane. This was a race against time in multi-shift operations. The pillar surfaces had to be broken off and remodelled. For the single-sided formwork for the up to 14.40 m high walls, 160 m2 of the high-performance wall formwork system Mammut 350 were employed. STB support frames with extensions secured the concreting work in two cycles to an initial height of 12.40 m.

This was followed by a no less challenging stage: the upper section of the weir pillars. To pour the unconventional shapes of the cantilevers, complex wooden panels had to be integrated into the formwork. Using Revit BIM software, it was possible to minimize the facing waste and the workload for the special construction.

Space-saving climbing
On the cantilever the KLK climbing system was hooked into the embedded cones of the previous construction phase. The modular MEP shoring tower was installed on the climbing unit comprising the wall formwork and a working scaffold and then reinforced with scaffold tubes. It was thus possible to continue working safely both at a height and in the space below. Because of the high concrete loading some of the H20 wooden formwork girders had to be replaced by steel girders. The KLK climbing scaffold provided the workers with an optimum, 2.30 m deep platform from which to perform their tasks.

In October 2019 the first highlight at this construction site was celebrated: The 140-ton steel weir gate, with a length of 30 m and a diameter of 5.3 m, was transported from Emsland via the Rhine and the Main to Viereth, where it was lowered precisely into the new concrete guides and rotary shafts of the outer and central pillars using two 500-ton mobile cranes. Upon completion of the connection work and trial operation, as of Christmas 2019 the right-hand weir field was once again ready to be used for flood water regulation. Since March work on the left-hand weir field has been proceeding at full speed. Here, the construction company is profiting from MEVA’s experience in the field of special construction. To reduce the costs, the wooden panels were modelled the previous year so that they can be now used again during the repair of the second weir field. A total of 30 wooden panels with a maximum size of 6.80 x 2 m were created for each pillar side. The official opening of the completely overhauled weir is planned for the end of the year.