ISG goes over the top at the O2
A walkway suspended 60m above ground at one of Londonís major concert arenas is destined to become a must-do for adrenaline junkies
O2 Roof Walk evening skyline visualisation
“It’s certainly one of our more unusual projects,” says ISG project director Eamonn Wall of his firm’s involvement in the latest London attraction for thrillseeking tourists. That’s an understated view, as the ISG-led project team isoverseeing the construction and erection of a narrow footway over one of the capital’s most famous entertainment hotspots. If balancing precariously while you walk across a gently heaving synthetic fabric path suspended 5m above the roof of the rebranded Millennium Dome qualifies as entertainment, then the newly launched Up atThe O2 roof walk is the latest attraction to what site developer Anschutz Entertainment Group is determined will become a mecca for sightseeing and entertainment.
With the O2 Arena set to be handed over to the Olympics organisers within the next few weeks in readiness for it to become the venue for the gymnastics at this summer’s London Games, the race is on for the site team to get the walkway, viewing platform, access structures and changing facilities up and running so that the attraction is ready for the first influx of spectators. “The Arena will be handed over to the Olympic organizing committee on the 10 June and our completion ties in with that date,” says Mr Wall. “The O2 has proven to be very popular as a concert and sports venue, but the walkway is part of the plan to have something to help deliver footfall to the area when there isn’t a concert.” The project itself is effectively separated into two stages, with work going on concurrently: the ‘airside’ stage (all work going on above the dome roof), and the ground work (everything that is focused on the ground level facilities and launch platform). To help with the fabrication and rigging of the walkway, ISG has brought in Bristol-based fabric structures specialist Base Structures in a bid to hit its tight deadline. It is manufacturing the 3 m-wide walkway and side safety wings and installing the system across the roof of the dome under its deal with ISG, while the more mundane steel framed access tower and changing facilities are built at ground level.
While the roof of the 12-year-old Millennium Dome is looking good for the foreseeable future, in construction terms it is a fragile roof – albeit one that acts like a giant bouncy castle – and both the design team and installation team have to take that into account. Fortunately, lead designer Buro Happold has been involved in the dome in all its different guises since its inception in the mid-1990s. Understanding exactly how the structure can and cannot be loaded has been vital in turning the project around from a client’s daydream into a fully blown tourist attraction in scarcely more than six months. “We first became involved in September 2011, when we were invited to negotiate the contract,” says Mr Wall. “By the end of October we had been formally appointed.” But it took a further four weeks for work to start on site.
That extra lead-in time was fundamental in enabling ISG to line up the delivery of the scheme. “With such a cramped site, we realised we needed to have as much prefabrication as possible. That’s why we went for the crosslaminated timber modular buildings for the changing pavilions and the steel frame for the central viewing platform and the access tower,” says ISG senior construction manager Jon Clayden. The walkway itself is made from a PVC type 2 coated polyester at Base Structures’ Bristol headquarters and brought to site in sections: 12 on the ascent to the viewing platform, another 13 providing the descent back to ground level. For the steeper sections of the walk – which starts at an incline of 30 degrees – the walkway is ribbed and treated to help improve grip. It also features white ‘wings’ at either side of the blue-surfaced walkway.
These provide an extra safety zone, but also blend into the white of the dome’s skin so as not to take the edge off the sense of precarious adventure. Steel tubes form a ribcage for the walkway throughout its length and will enable handrails to be attached. At the centre, each radius of the 190 m-long walkway is directly connected to a steel viewing platform that is bolted into place in-situ.
“Obviously there can’t be any hot works in operation up there, so everything is mechanically fixed,” says Mr Clayden. The whole construction process has thrown up challenges that have tested the team, from the speedy turnaround time of the entire scheme through its design and on into the build process (see box above). But, says Mr Clayden, the gain has been worth all the pain. “And they call this work,” he grins as he surveys the view of London’s skyline from the edge of the 60 m-high viewing platform. Not for much longer. Within a few weeks, work on the walkway will have finished and the only people admiring the view will be paying visitors, seeking that adrenaline shot and to share a seagull’s view from one of London’s iconic structures.
Article originally appeared in the 3 May 2012 issue of Construction News. Reproduced with permission.