Construction World August 2016

PRECAST

Gautrain platform extended with PRECAST ELEMENTS By Chrissi Maria

The Gautrain Station at the OR Tambo International Airport (ORTIA) has recently been extended by 55 metres in order to accommodate a further two Gautrain carriages and bring the station capacity up to a full four-car train set.

“When planning this project we had to address multiple challenges including our proximity to people, airport traffic, live trains, the adjacent hotel – and of course we had to consider all these when planning access to do the work,” says Stefanutti Stocks Civils’ contracts director, Mike Stevenson. “We considered erecting a gantry from which we could pick up the precasts and lower them into place, however we would have been snookered on the southern side, due to the hotel and the through road.” Interesting aspects of the project • A protection deck, consisting of a girder system that spanned the 18-metre wide main access road into the airport, was designed and constructed prior to work being allowed to commence over vehicular traffic. • The demolition activities had to be undertaking in a way that reduced environmental impact in terms of excessive noise and dust pollution. In particular noise levels, if not controlled, can prove very disruptive, to guest in the airport hotels and customers using the Gautrain. • To accommodate the increased loading of the structure the struts were transversely post-tensioned and the existing viaduct was longitudinally tensioned. • A new 68-ton steel roof canopy was manufactured and installed. • The construction method had to take into consideration the mere 150 mm distance between the southern side and the adjacent multi-storey City Lodge carpark. “The key to the success of this project included a professional team and good plan- ning that started from the conception phase of the project,” concludes Deyzel. “Our site motto was to ‘do it right the first time’, and by setting ourselves realistic goals, we were successful in achieving them.”

Turner & Townsend, appointed by Bombela Concession Company (BCC) as project managers, adjudi- cated Stefanutti Stocks Civils as the preferred contractor, whereafter BCC awarded the construction contract to Stefanutti Stocks. Work on site started in July 2015, and the completed platform was handed over in May 2016. The scope of work undertaken by Stefa- nutti Stocks Civils included the design and construction of the entire station extension and all associated works. This included the modification of existing infrastructure to accommodate the new installation; the installation of precast struts; the manufac- ture and installation of precast slabs and balustrade walls; the manufacture and instal- lation of a new steel roof canopy with fire escape staircases; and all platform finishes on completion. The precast concrete elements included 5 ton struts and 20 ton slabs and balustrade walls, which were manufactured off-site. Prior to the installation of these precast >

struts and slabs, the existing parapet walls were saw cut using a diamond rope-and- blade cutting system. The project included a number of unique and interesting aspects, both in terms of constructability and the technology required to achieve the necessary construction. Not only did the entire installation of the platform extension take place at a height of 18 metres above ground level, it was also the first time that an upgrade to the Gautrain station has been undertaken, while train operations continued as normal. “Our collaborative brainstorming and feasibility studies resulted in innovative ways to execute temporary works,” says Glen Deyzel, Stefanutti Stocks Civils contracts manager for the project. “We had to consider an installation methodology that would allow us to achieve our best production and address all safety, environmental and construction risks.” Risk considerations included the project prerequisite that the trains were to remain operational at all times. Furthermore, the access road, directly above which construc- tion took place, also needed to remain operational at all times, as it was an airport entry point. The confined working area as well as the weight of the precast elements that were assembled to build the platform required the use of what is said to be the largest tower crane in Africa. This crane was utilised at the platform extension at a capacity of 26,1 tons at a radius of 40 metres. This crane has a maximum capacity of 10 tons at a radius of 82,6-metres.

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CONSTRUCTION WORLD AUGUST 2016