Manchester Stadium Cable Net Roof Structure

Building Tension, Modern Steel Construction December 2003, describes the various structural systems employed in the design of the City of Manchester Stadium. The cable stayed roof structure, designed by Arup and Associates, London, is of particular interest. Some noteworthy aspects include:

• The cantilevered roof structure is supported by a mast and cable net system. Masts are as tall as 70 meters (230 feet). Five or seven forestay cables radiate from the top of each mast to support the forward, cantilevered portion of the roof structure. Pairs of backstay cables, running from mast tops to the ground, stabilize the masts and resolve the horizontal forces in the forestay cables.
• A grounded tension ring stabilizes this cable system against varying load conditions. The tension ring is a group of cables tying all the forward ends of the forestay cables into a closed circular loop. At four locations, the tension loop itself is tied to the ground by its own stays. These stays are tightened, prestressing the entire tension ring. The prestressing is sufficient to create a downward force in the tension ring that is equal to the largest upward force generated in the roof structure by wind uplift, thereby ensuring that the overall cable system remains in tension under all loading conditions.
• The cable stays, masts, and tension loop form an independently stable structural system, providing more flexibility in construction sequencing. The cable system could be erected separately from the structural steel framed roof system, and the roof system itself could be completed in phases, as the programmed uses for the stadium have changed.

More Information:
Arup web site: City of Manchester Stadium, UK