Helical staircase at Tivoli, Copenhagen

Steps are supported by the innder stringer and have no connection to the elevator
Helical staircases in CRC

With the high strength of CRC and the possibilities of redistributing stresses that is achieved by using a fibre reinforced UHPC, it is possible to design structures with much more freedom than can be achieved with conventional concrete. One of these options is to produce slender helical stairs with a large cantilever of the steps, thus allowing a lot of torsion in the design.

Most helical stairs in CRC make use of CRC JointCast, where the stair is produced in a number of parts (to keep mould costs at a manageable level) that are subsequently connected using JointCast - typically with joint widths in the range of 100 mm. 

The first helical staircase in CRC for the UK market has recently been installed for the Sidney Stringer Academy in Coventry, but as the stair is being finished at the moment there are no pictures available. Kier was the main contractor for the project, WSP were the engineers and architects have been Sheppard Robson. Kier have documented installation of one of the flights in this link where a time lapse video is shown.

Helical staircase at Tuborg Boulevard

The diameter of the stair is 6 metres

Vertical loads are carried by a column shell
Helical staircase in Copenhagen

Beton-Tegl A/S has produced a special helical staircase in CRC for one of the office buildings on Tuborg Boulevard in Copenhagen. The staircase is designed by the architects Arkitema and is centrally located in the atrium of the building. The staircase has an outer diameter of 6 meters. The inner handrail also acts as a helical beam and the steps are cantilevered 2250 mm from this beam, which has to take a fair amount of torsion. The spiral beam has a thickness of 150 mm and a height of 1500 mm.

For the staircase to appear as slender and elegant as possible the steps have a thickness of 30 mm towards the atrium and this thickness increases to 100 at the root - against the handrail.

The staircase has been precast in 16 repeating elements - 4 for each floor - and is joined on site by CRC JointCast. The stair has been painted with a white concrete paint and the steps are covered in hard wood timber.

Tuborg Nord C are the owners of the building, NCC Danmark was contractor and the calculations have been made by Rambøll A/S. 

Article in Concrete Engineering International

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