Demanding applications in falsework & formwork

By Helen Wright11 March 2011

Paschal’s leading-edge circular formwork with trapezoidal girders (TR) were used to aid the construc

Paschal’s leading-edge circular formwork with trapezoidal girders (TR) were used to aid the construction of a 12.5 m high round tank for a natural gas plant in Kerpen, Germany.

Technical and challenging builds are driving innovation in the falsework and formwork sector. Helen Wright reports.

Manufacturers of falsework and formwork systems are keeping pace with the challenging architectural demands of modern, technical projects. From supporting the construction of a new airport control tower to enabling the restoration of an historic building, new products and techniques are emerging all the time.

Often battling against headwinds such as keeping costs as low as possible and adhering to aggressive schedules, key companies in the sector continue to develop the versatility and efficiency for which the falsework and formwork sector is renowned.

Indeed, Paschal faced a test of its formwork's capabilities when it was approached last year to provide support for a demanding technical build.

The company was selected to install a circular formwork system as part of the expansion of a natural gas plant in Kerpen, Germany. And the pressure was on - the contractors chose the circular system in order to get the job done faster than otherwise would have been possible with conventional wall form shuttering.

Paschal's circular formwork with trapezoidal girders (TR) were used to aid the construction of a 12.5 m high round tank with an insider diameter of 32 m and 350 mm wall thickness. The formwork consisted of 9.75 m high preassembled segments, adapted to the given radius and raised by another 3 m directly on the site.

TR formwork features a 21 mm thick birch plywood shell suitable for nailing, and each segment features two longitudinal girders to ensure stability and to accurately match the circumference of the structure.

A square metre of finished formwork can withstand up to 60 kN fresh concrete loads, but features only 0.28 tying points - technology which Paschal says is a perfect fit for the demanding applications of modern, technical builds.

"Every week, we were handling about 400 m2 polygonal scaffolding modules, 400 m2 circular formwork, 200 m2 concrete protection bands, joint seaming and related fittings, as well as about 200 m2 wall reinforcement, shuttering and concreting - and all this in a very confined space," Rudolf Huth, director of the technical department at site contractor Bruno Klein, explained.

"As walls were erected in segments, these tasks could not be performed at the same time or overlap each other. It was all done step by step in one progressive sequence," he explained, adding that each of the six steps took a week to complete.

Paschal said this step-by-step method for both formwork and concreting, together with the fact that formwork segments as high as the given structure were used, provided "significant savings" on the costs of climbing systems.

In addition, this modular work method has the clear advantage of requiring fewer formwork segments, reducing rental and transportation costs.

The pressure to keep costs down is an ever-present demand throughout the construction industry, and the formwork and falsework sector is no stranger to the challenge of striking the balance between the fastest possible erection and maintaining high standards of safety on site.

Doka has taken its shoring technology a step further with the launch of a new product that is very lightweight and yet robust and safe on site. The company's new Staxo 40 towers feature a frame which weights between 15 kg and 24 kg, and as such can be moved by just one person - key to allowing faster erection and dismantling.

The frame also features an H-shaped geometry which makes it possible to have gapless, full-area assembly decks not only inside the towers, but also between them as well. This is a key safety feature which, together with the new system's anchor points for personal safety harnesses and integrated safety catches, contributed to the new Staxo 40 and larger Staxo 100 load-bearing towers winning the European award for safety in structural engineering from Spain's General Council of Technical Architecture in November last year.

More than 8000 Staxo 40 frames are currently being used on the construction of the Shemouk Twin Towers project in Doha, Qatar. The system's low unit weight and small number of separate components enable a three-man crew to assemble each 7.75 m tower in around 20 minutes.

Site engineer Miled El Dada said the ability to erect the towers horizontally also granted the contractor "big time savings, greater flexibility in terms of our time schedule, and a very safe way of working".

Fuvi is also targeting increased productivity with the launch of a new slab/beam system that it claims allows for the forms to be removed and transferred on within four days, bypassing the need to wait 14 to 21 days for the concrete to harden first.

The new Honey MDC system features a drophead design with a 500 x 1000 mm main panel size and 90 mm thickness and a range of smaller panels and combinations.

The drophead comprises a steel core bar, a small plastic panel head to support the concrete labour beam at all times, and a plastic outer shoulder which supports the adjoining Honey slab/beam panels.

When the panel forms are removed by releasing the outer shoulder down the supporting core bar, the drophead remains in place supporting the full weight of the concrete slab.

The slab remains continuously and fully supported throughout the curing phase; eliminating the need to wait 14 to 21 days for the slab/beam to fully cure before removing the formwork to its next location.

The new system offers "easier formwork constructability, faster formwork erection and removal times, reduced formwork costs and increased re-use cycles," according to Fuvi.

"Most importantly, the new system offers significant formwork investment cost reductions," the company said. This means that instead of buying three sets of slab/beam formwork to meet a typical requirement and installation schedule, a contractor need only invest in a single set plus additional low cost props for up to three installations.

The slightest hold up during the initial phases of any modern build can have repercussions that affect the project deadline.

Indeed, Meva said one of the central challenges to providing the forming for the new and highly technical Mixed Oxide Fuel Fabrication facility (MOFF) in Aiken, South Carolina was the contractor's "aggressive" construction schedule for the placement of 130,000 m³ of concrete.

Commissioned to go online in 2015, the initial phases of construction are currently underway at the facility, which is the first nuclear project to be built in the US in over 20 years, and only the second plant of its kind in the world.

Meva engineers applied a simple but effective principle to the formwork implementation in order to save as much time as possible - they reduced job-built or custom expenses to a minimum by using standardised Meva equipment.

The company's Imperial wall formwork was specified because of it sports a maximum load capacity of 100 kN/m² which allows rapid pours in wall heights up to 7.3 m and 1.8 m wide.

Over 9800 m² of Imperial have been placed on the MOFF site and Meva's KLK climbing scaffold, R460 props and scaffold brackets and MEP shoring system are also being used on the project.

The ability to provide a comprehensive and versatile package of products is often central to gaining access to the most challenging projects. Harsco Infrastructure demonstrated this when it undertook a demanding project this winter to install a temporary, rolling roof for a Dutch university - a job which required the company to provide a comprehensive formwork, shoring, encapsulation, mast-climbing, suspended and powered access, scaffolding, staircase and edge protection package.

Harsco worked closely with the main contractor, Hurks van der Linden, and with its roofing system partner Haki to install the Hakitec 750 rolling roof. The temporary structure shielded the site from the weather so that construction work on Utrecht University's new science building could remain on schedule.

The roof was designed to be opened and closed by the on-site scaffolding team during the construction work so that materials could be craned into the building. Towards the end of the project, Harsco and Haki even raised the 1446 m2 roof by an extra storey to create sufficient space for the final construction stage to take place.

Similarly high precision work is currently underway on several sites at the new Berlin Brandenburg International Airport in Germany, including the construction of a 72 m control tower which forms the hub of the project.

Contractor Züblin is building the tower, which features a 66 m high tapered concrete shaft, a three-story ground building and elliptical control room.

Assembled by Züblin, an all-round wooden girder formwork was used on the outside with framed formwork inside. A self-climbing formwork (SCF) from Harsco was used to climb step by step with the building, aided by inbuilt hydraulic jacks. Such SCF systems remove the need for cranes and allow tall buildings to be built efficiently, without vibration.

Four hydraulically extending SCF platforms measuring 9.55 m x 3.86 m were used for the carcass work in combination with fair-faced concrete panels from Westag & Getalit (W&G).

The bare shell of the tower took almost seven months to build, but cycle times were consistent, according to Züblin project manager Christian Bittner. The airport is scheduled for completion in October this year.

"The use of the self-climbing formwork in combination with W&G panels produced reliable cycle times and very good concrete surfaces.

"Reinforcing steel bars with a length of up to 13 m were laid and aligned from a four-story scaffold rising above the formwork elements on the climbing platform. Concreting took place in 5.4 m segments at four-day intervals," Mr Bittner explained.

He described the project as "a choice example of formwork".

Developing consistent and more intuitive formwork systems continues to be a core driver for new products and techniques in the sector, but such advancements are no mean feat when modern projects are increasing in complexity and technical specifications.

Nevertheless, the key companies have continued to demonstrate an adaptability and dual commitment to efficiency and safety that has set them up to take on the challenge of demanding applications in the future.

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