Saxon’s skywalk wins Steel Award

The Saxon hotel skywalk project, a spiral walkway bridge that winds its way through the wooded grounds of the Saxon Boutique Hotel, Villas & Spa in Sandhurst, Johannesburg, has won the Tubular category of the Steel Awards 2011.

The judges said of this creative skywalk: “It’s like walking inside a giant python and eventually ‘popping out’ in the jungle. Then, looking back we see that the ‘python’ is 27 tons of tubular art with sleek, smooth and flowing lines.”

The Steel Awards 2011, held recently at Emperor’s Palace in Kempton Park, Suncoast Casino in Durban, and the One&Only Cape Town, was hosted by the Southern African Institute of Steel Construction (SAISC) with the Aveng Group the main sponsor.

The Saxon skywalk connects the main hotel and conference facilities to three luxury villas situated in an indigenous forest on the southern side of the property. The project includes lifts at both ends, providing access to the walkway at the hotel end and to underground parking at the villa end.

According to the project team, the use of tubular steelwork for this project was a given due to its “strength-to-slenderness” capability. The team notes: “The brief was to provide an unobtrusive yet elegant means of moving safely between the hotel and the villas, while being able to enjoy the ambience of the location, and this was achieved.”

The skywalk, fitted with timber flooring, glass handrails down both sides and a roof made of a canvas canopy fitted to thin tubular rafters welded across the top chords of the bridge, spans 76 metres from lift shaft to lift shaft and has five intermediate supports hidden in the forest. The diameter of the spiral is 2.85m and the main chords are equally spaced around the spiral, with the two bottom chords inside the spiral and the two top chords outside the spiral.

Since the skywalk curves both horizontally and vertically over its length, it was impossible to fabricate its spiral diagonals using a fully rolled spiral tube. They were rolled in partial circular segments instead. These segments were then assembled with the main chords in special jigs and located by thread-bar studs at each intersection point utilising backing sleeves to obtain full penetration welds at all pipe joints.

Detailing of the structure was an achievement in itself and required an experienced detailer utilising a 3-D detailing package working in close conjunction with both the design engineer and the steelwork contractor to develop a set of practical and workable drawings.

The structure was fabricated in segments that allowed easy transport to site. However, getting the segments onto site and to their final installed locations was not a simple exercise at all.

The segments varied in length between ten and thirteen metres and the shorter straight sections were able to be taken through the large but tight fit main entrance gate. However, the long, curved sections could not be taken through the gate or up the driveway with a horse and trailer and had to be craned over the high boundary wall and placed on a purpose-made trailer for the final leg of the journey.

The sections were then carefully hoisted by crane through the trees and positioned onto temporary scaffold towers before being aligned and welded together in-situ. The necessity not to damage the trees was non-negotiable and required many tedious re-setups of the mobile crane before they could be finally positioned.

The chosen method of construction of the walkway worked out well and was aided by accurate detailing and good communication with, and assistance from, the professional team, enabling it to be completed in time for the opening of Phase Two of the Saxon Hotel’s extension project and ultimately for 2010 World Cup visitors.

One member of the project team said: “From early in the design stage I knew this was a Steel Awards winner. But then when I saw where it had to go through in this natural forest, I thought we may have bitten off more than we could chew. But the end result is testimony to what can be done with willpower… and steel.”

The judges reiterated the outstanding achievements of this project: “It represents an exceptional use of tubular steel as it snakes through the forest, seemingly unsupported, giving the impression at night of a fibre-optic cable floating in mid-air.”

The Aveng Group was the main sponsor for Steel Awards 2011 along with Cadex SA; Association of Steel Tube and Pipe Manufacturers of South Africa; Stewarts and Lloyds; Macsteel; ArcelorMittal SA; B&T Steel; Cosira Group South Africa; First Cut/Kaltenbach; Group Five; NJR Steel; Tubular Holdings; and Vital Engineering.