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Concrete: Jewel on the crown

A dramatic new building is taking shape on the Antwerp skyline that is posing a challenging test formwork and falsework designers. NCE reports.

The Zaha Hadid Architects-designed New Port House, which pays homage to the city’s diamond trade, includes a fair-faced concrete support structure that tested the technical capabilities of the formwork supplier.

New Port House Antwerp

Formwork support: A range of different formwork products has been used to build the complex concrete support structure

Antwerp harbour is one of the largest in Europe, and investment in new infrastructure in the Belgian city is intended to enhance that status.

Among the projects under construction - and certainly the most striking - is a new headquarters for the Antwerp Port Authority designed by Zaha Hadid Architects.

The Nieuw Havenhuis (New Port House), which is due to open next year, will accommodate around 500 employees and enable the organisation to bring all its staff under one roof. It is an extraordinary project, which utilises the restored former Kattendijk dock fire station - a listed building - and then adds an angular steel and glass building that appears to float over the top to a height of 46m above ground.

The old fire station serves as a form of podium for the new structure, whose spectacular shape is reminiscent of a ship and, when complete, will offer breathtaking views of the harbour and the city. The façade of the floating structure is composed of triangular sections of glass, which the architect says will generate a continuously changing interplay of light reflections, and thereby serve as an ever-present reminder of Antwerp as the centre for diamond trade.

North-south axis

The new building, which runs on a north-south axis parallel to the Kattendijk dock, has been constructed using modular methods. A total of 1,500t of steel was used to construct six pre-assembled modular elements, designed to be lifted into place and fitted together on site.

Support for these modules is provided by a 22m high, asymmetric concrete structure that straddles the old building. It has three sculptural columns, one of which lands outside the building on the south side, while the other two sit inside the courtyard of the former fire station.

One of these legs contains a core, with lifts giving access to the floating structure.

Belgian contractor Interbuild, a subsidiary of Bam, was awarded a fixed price contract valued at €49.9M (£39M) to construct the new building, and started work in October 2012.

A separate grant paid for the refurbishment of the old fire station.

Project details

Project: New Port House (Nieuw Havenhuis)
Location: Antwerp, Belgium
Contractor: Interbuild
Architect: Zaha Hadid Architects
Construction start: October 2012
Scheduled completion: Autumn 2015
Formwork specialist: Doka
Design consultants: Studiebureau Mouton, Ingenieursbureau Ingenium, Daidalos Peutz, Origin, FPC, Bureau Bouwtechniek

One of the biggest challenges is constructing the massive concrete support structure to the standard demanded by the architect’s design. It has 12 lateral surfaces, all at different angles, and the design calls for it to be constructed in fair-faced concrete, with the form-ties and joints carefully designed to create a specific pattern.In addition, all form-ties have to be attached to the concrete surface at 90º angles.

Due to the complex shape and the nature of the white, self-compacting concrete needed to achieve the required finish, the formwork had to be capable of withstanding pressures of up to 100kN/m² from the concrete.

Interbuild appointed Doka to provide the formwork, making use of the firm’s fair-faced concrete competence centre, which is based at its headquarters in Austria.

Sophisticated formwork concept

“Doka won us over with a sophisticated formwork concept,” says Interbuild project manager Tom Van Hauwe. “The complex geometry of the structure requires know-how and experience.”

Doka divided the 22m high support structure into five segments ranging from 3.7m to 5.5m in height, and then created a custom 3D model of the formwork requirements - including form-tie and joint pattern - for each pouring section.

New Port House Antwerp

Artists impression: The Zaha Hadid structure straddles the older building

The firm says that attaching the form-ties and developing the forming timber boxes during the planning stage “required a particularly high degree of creativity”.

To connect the outer formwork, Doka developed a special angled waler capable of accommodating the different wall inclinations and dealing with the high concrete pressures.

Once formwork planning was completed, Doka started to pre-assemble the inner and outer formwork for the five pouring sections, using a range of its standard products in addition to the specially fabricated walers.

Its large area formwork product Top 50 serves as the base, and was fitted on site with the 18mm thick multi-ply formwork sheets that ensure the fair-faced concrete result. Top 50 panels on the lateral surfaces were shored up by Doka’s Staxo 100 load bearing towers, while the timber beam formwork was supported by Eurex 60 and T7 spindle strut.

Doka formwork systems were also used to construct the building’s new core and two levels of underground parking.

The 30m high building core is also built in fair-faced concrete, and was erected using MF240 climbing formwork in combination with Framax Xlife framed formwork.

The firm’s new Dokadek 30 panel floor formwork was used for in situ concrete works in the underground car park.

One stipulation by the Port Authority was that New Port House should have a high level of sustainability, and the project has already achieved a provisional Breeam certification of “very good” on the basis of the design.

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