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| With an overall length of 465 m, the River Suir Bridge is by far the biggest cable-stayed bridge in Ireland. Doka is supplying the entire formwork solution for the works on its 106 m tall pylon. The contracting consortium of Dragados, NTR and Royal BAM is using the Doka climbing formwork system SKE 50 to form, pour and reinforce the pylon legs in a weekly cycle. |
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The Irish government is making massive investments in modernising and upgrading the country’s top-level transportation infrastructure, with over 35 billion euros’ worth of construction planned for the period up to 2015. The aim is to enhance the competitive pull of the Emerald Isle in the international business relocation stakes, and to put the dynamic economic growth of recent years onto a firm long-term footing.
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The national action plan “Transport 21” focuses capital spending on the construction of new, high-capacity regional transport links. A current example of this is the approx. 25 km long by-pass being built around the county town of Waterford in the southeast of Ireland. With its 108 m tall pylon and a span of 400 m, the 465 m long cable-stayed bridge across the River Suir is not only by far the most challenging contract section of this major road-building project, but also the biggest cable-stayed bridge in the whole of Ireland. Doka is supplying the entire formwork solution for this technically complex bridge-building project, including detailed formwork planning that gives impressive testimony to Doka’s outstanding problem-solving capability.
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The legs of the A-shaped bridge pylon are inclined by 15 degrees and characterised by their parabola-like cross-section. To erect the 108 m pylon, the contracting JV of Dragados, NTR and Royal BAM is relying on the high-performing automatic climbing formwork Doka SKE 50 and profiting from the know-how amassed by the Doka Formwork Experts in over 20 years in the automatic climbing field. “This is the first time we’ve ever worked with automatic climbing technology. The Doka formwork solution convinced us right from the word “go”. In particular, being able to jump the formwork units so quickly and safely using hydraulic cylinders, and set up and strike the formwork in such a straightforward way, really helps work to move ahead rapidly”, comments contractors’ supervisor Raphael Torres, summing up their positive experience with the Doka automatic climbing formwork SKE 50. A total of twenty SKE 50 automatic climbers and 300 m² of Large-area formwork Top 50 are in service here. The profiled timber formers, made with complete dimensional accuracy by the Doka “Ready-to-Use” Service, enable the form-ply to be exactly adapted to the complex cross-section. Due to the high number of re-use cycles, and the pronounced bending of the form-ply, the site engineers decided to face the profiled timber formers with Dokaplex formwork sheets. This high-grade multi-ply sheet made of Finnish birchwood delivers a flawless, uniformly smooth concrete finish even after very many repeat uses. Up as far as the deck slab, the legs of the pylons are being constructed with a solid cross-section, for structural-design reasons. From the fifth casting step upward, they are being constructed with a hollow cross-section. The inside shaft is being climbed using the profile-guided Climbing formwork GCS. Two GCS climbing units are in action on each pylon leg. To ensure optimum transfer of the loads acting on the formwork, the Climbing formwork GCS is reinforced with massive steel components from the Doka dam formwork system. The high safety standard assured by this custom solution, coupled with its cost effectiveness thanks to the use of rentable standard components, were what won over the site engineers.
At a height of 60 m, the pylon legs merge into an approx. 48 m pylon head. In the last three casting sections before the point where the legs merge, the platforms have to be continuously adapted to the changing space conditions. For the work on the upward-tapering pylon head, the platforms are adapted to the automatic climbing formwork as required by the new cross-section. All the components of the self-climbing units used for the work on the pylon legs can be re-used here, keeping the commissioning quantities to a minimum. The Top 50 large-area formwork also stays in use, following minor modifications. From the 18th casting step upward, the site crew have to mount the fixing sleeves for the massive bearer cables. As it is not possible to place form-ties in these areas, the Top 50 large-area formwork is given extra reinforcement with rentable standard components.
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As the contracting JV had not had any previous experience with automatic climbing formwork, the site crew are being given intensive support and assistance by experienced Doka Formwork Experts and field service technicians. Alongside detailed formwork planning, the Doka service package includes stalwart assistance for the site crew with first-time assembly of the formwork equipment, and ongoing support of the site by Doka Formwork Experts. The platforms for the SKE 50 automatic climbing formwork, and the extra-large Top 50 elements, are assembled on-site under the professional guidance of an experienced Doka field service technician. Besides this, the field service technician instructs the site crew on correct handling of the formwork equipment, and passes on the basic principles needed to ensure the very greatest operational safety. This helps to ensure troublefree forming operations and get the most use out of the efficient formwork solution, right from the very first casting section. The wide working platforms, enclosed on all sides, and the fact that the automatic climbing formwork is anchored in the concrete at all times, ensure a maximum of workplace safety, even when high wind speeds are encountered.
“The support we’ve had from the Doka Formwork Experts, both in the planning phase and while carrying out the works, has been a crucial factor helping us to meet the ambitious timetable. Specifically, the thorough introductory training given to the crew by the field service technicians in how to use the new equipment saved a lot of time and expense and made a big contribution towards the safe, smooth forming operations we’ve been having here”, says Raphael Torres, who is in no doubt as to what this extensive on-site service has meant in terms of successful project implementation. Thanks to these thorough forming preparations, the site crew have been forming, reinforcing and pouring this remarkable pylon in a weekly cycle.
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| Coupled with the generously sized working platforms, which are enclosed on all sides, the fact that the climbing scaffolds are anchored to the concrete at all times ensures a maximum of workplace safety, even in windy conditions. |
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