City of Manchester Stadium Arup Associates
The stadium takes the form of a shallow bowl lined with tiers of precast concrete seating. They are sheltered by a roof canopy - a series of rafters extending from the eaves - which in turn is supported from a cable-net structure.
The rafters - ranging in length from 34-51m - rest at the eaves on V-shaped steel struts;14m from the tips, they are suspended from fore-stay cables which are tied back to masts at the perimeter of the building. Each rafter is connected to its fore-stay cable by means of a CHS strut and a 1,150mm-diameter disc to which a pre-tensioned catenary ring of four 45mmdiameter cables is clamped.
A CHS prop transfers the self-weight of the disc and cable to the rafter.
The rafters are steel boxsections 300mm wide and taper from 900mm at the forestay supports to 450mm at the tips. A box-section profile was chosen for structural stability and to reduce maintenance - there are no edges to gather dust and dirt or to accommodate roosting birds.
A standing seam aluminium roof covering rests on galvanised top-hat sections which in turn are supported on 150mm-deep perforated aluminium structural liner trays. The trays span 4m and rest on the bottom flanges of 254 x 146mm UB purlins. The arrangement provides a clean soffit to the roof and encloses acoustic insulation and structural bracing.
A recessed gantry is set in the roof to contain flood lighting, house lighting and speakers for public address and warning systems. An adjacent walkway allows access for maintenance. From gantry to rafter tips, the roof is clad with polycarbonate sheet to enhance daylight and promote grass growth.