Construction World December 2018

Building Contractors

WINNER and HIGHLY COMMENDED in the AfriSam Innovation Award for Sustainable Construction

NEW DISCOVERY HEAD OFFICE November 2014 marked the start of an epic journey whereby the Tiber/WBHO Construction Joint Venture undertook the construction of the behemoth new Discovery Head Office in the Sandton precinct. The project would become the largest single-phase commercial office development in Africa.

T he construction included a nine floor super basement with an overall foot print of approximately 225 000 m 2 . Over and above the basements, three towers were constructed. The tallest rising 10 floors above the ground level. Total occupied floor space in the office towers consist of 110 000 m 2 . A total of 12 900 tons of high tensile reinforcing was fixed and approximately 132 400 m 3 of concrete was poured in to the structure. Construction innovation technology The two larger towers were joined together by means of post tensioned bridges over a central concourse, each consisting of a central set of lift cores, these cores were climbed utilising a PERI climbing system and concrete was placed utilising a Putzmeister 36 m boom pump that was lifted between the shafts floor by floor. Due to the programme and sequence of the construction, a total of eight tower cranes were erected to distribute material across the site. Some of the tower cranes required temporary columns in order to tie and jack them to the required higher positions. These columns were then later removed. The massive atriums were particularly challenging with structural steel beams spanning from edge to edge (34 m spans), the skylights were fully glazed utilising a moving gantry with hoists to place the large panels. The fact that a Boeing 737 could be placed in the west tower atrium without touching any edges is testament to the scale of the atrium. A multi axis laser scanner was utilised to plot the atrium slab edges (as built) to assist in streamlining the installation of the balustrade channels. Over all, approximately 4 km of internal atrium/concourse glass balustrade was installed and a further 1,5 km of stainless steel balustrade was installed on the podium and roof levels. A total of 1 300 tons of access scaffolding was utilised within the atriums and concourse areas. One of the most challenging aspects of the new Discovery Head Office in terms of construction was the construction of the iconic cantilever “nose” of the west tower facing the corner of Katherine and

Rivonia. The cantilever extended 20 m over the podium level. The Nose consisted of three transfer beams constructed on the podium level that carried five temporary columns. These five columns supported six levels of structural steel and reinforced bon-dek concrete slabs until such time that the transfer beams on the roof could be completed. Once the beams were post tensioned and the support columns released, the temporary columns and transfer beams would be demolished and removed. The 3,5 m high, 2,5 mwide transfer beams spanned a maximum of 34 m. The beams on the roof level consumed a total of 700 m 3 of 70MPa low heat of hydration, self levelling concrete as well as approximately 170 tons of reinforcing. Corporate social investment Tiber/WBHO Construction employed staff from the local community in an effort to ensure the local and surrounding communities benefitted in terms of employment and skills development over the duration of the project. Design innovation The three towers consist of 20 escalators, 15 passenger lifts, three fire/ goods lifts, two visitor lifts, one MIP visitor lift, three goods lifts and 12 staircases. The roof consists of a 620 m running track covering the east and west tower, a soccer court, a multi-purpose court, a yoga deck, 200 m 2 of planted landscaping. Vendors within the west and east tower include: Woolwoths, Vide E Café, Starbucks, Edgars connect, Clicks, Seattle coffee, Kauai to name a few. Attenuation tanks for domestic water store 850 000 ℓ with a further 500 000 ℓ for firefighting. Six generators will keep the building running with a storage capacity of 76 000 ℓ of diesel. Each floor across the three towers consist of six ablutions blocks, 10 fire escape staircases, six data patch rooms and half a

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