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ST 60 shoring towers moving from section to section

ST 60 shoring towers moving from section to section

19. August 2020

The building of a new warehouse at decommissioned Brunsbüttel nuclear power plant calls for formwork solutions that take little time to erect on site. Among other things, the Züblin project team used four movable shoring units from the Hünnebeck ST 60 system. This meant that the 5,600 m² reinforced concrete roof could be poured in sections without the need for multiple dismantling and re-erection of the approximately 15 m high formwork structure.

It was an impressive spectacle when, at the end of May, four large shoring units including the Topflex timber beam formwork placed on top were moved in succession on steel sections through the 116 m long and 48 m wide warehouse shell. The retraction of the formwork system was the prelude to the final construction phase of the colossal reinforced concrete warehouse, which is to be used for temporary storage during the forthcoming dismantling of the power plant. Four mighty winches brought the units, each consisting of 60 metric tons of shoring (height: 9.68 m) and a good 40 tons of formwork, with centimeter precision into their new position so that the second half of the 95 cm thick roof slab could be constructed, thus completing the carcass of the huge structure.

Little on-site assembly

The interim storage facility is a solid concrete structure with 85 cm thick walls standing on a 1.50 m thick reinforced concrete slab with a pile foundation. At a warehouse height of approx. 8.50 m (measured from the lower edge), 120 cm high craneway beams cantilevering by up to approx. 1.90 m are located along the center axis as well as on both longitudinal axes. So that all these huge components could be built in as little time as possible, there was close cooperation between the job scheduling department of Ed. Züblin AG (Northern Directorate) under the management of Werner Frömming and Hünnebeck’s project development department. The aim of the jointly developed formwork solutions was to minimize assembly times on the construction site as far as possible.

Pre-assembled formwork units for craneway beams

In action were project-adapted formwork solutions, which Hünnebeck supplied to the site ready for use. Pre-assembled units of the CS 240 climbing scaffold, for example, were available for pouring the craneway beams on the outer walls. In total, 72 platforms each 4 m long were in use. The brackets served as safe working scaffolds while taking up all the loads from the formwork and concreting process at the same time.

For the 116 m long craneway beam along the center axis, Hünnebeck designed special formwork tables using working platforms and the rapidly erected Gass aluminum shoring system. Here again, the company relied on extensive upstream assembly: the working platforms on which the Gass tables were mounted arrived on site as complete units ready for use. A total of 34 formwork tables were kept available on site, being simply moved to their next assignment position with a transfer fork. High-performance large-area beam formwork systems of ES 24 element formwork and H 20 large-area formwork were available for shuttering the exceptionally thick wall surfaces.

Safe and self-explanatory: the ST 60 modular system

However, the technical highlight of this unusual project was the “mobile” use of shoring units from the ST 60 modular system. On this project the scaffolders working with Hünnebeck’s innovative support system for the first time were impressed by the system’s simplicity and safety. The ST 60 modular system consists of just six basic parts, none of which weighs more than 15 kg.Three tower widths can be produced with only two frames: 113 cm x 113 cm, 150 cm x 150 cm and 113 cm x 150 cm. A load-bearing capacity of up to 240 kN per shoring tower (60 kN per leg) and the possibility of combining the system with aluminum and steel girders as well as with timber formwork beams (H 20 and R 24) ensure high loading and safe load discharge at typical working heights of 3 m to 15 m.

The ST 60 towers can be connected easily and flexibly to create high-strength spatial scaffolds. Load-bearing nodes are located on the ST 60 frames at 50 cm intervals, enabling force-locked connections in eight directions. At the warehouse construction site in Brunsbüttel, four ST 60 twin towers were connected in seven successive rows to form a movable shoring unit. The shoring extended up to the upper edge of the craneway beams at a height of 9.68 m. A working level was then mounted on top of this, which served as a base for setting up the timber beam formwork.

Carcass work almost completed

Meanwhile, the warehouse carcass is almost finished. The contractors’ team is highly satisfied with the formwork solutions provided: “A number things were unusual about this project. But together with our job scheduling team, Hünnebeck developed for all components really practical formwork solutions that took little time to erect on site.”

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