Visible from across London, the steel arch above the New Wembley Stadium is being supported at each end by INA spherical plain maintenance free thrust bearings. As well as being visually stunning, the 335m arch will also support most of the retractable roof that weighs approximately 7,000 tonnes. The arch alone weighs some 1,650 tonnes.
INA was chosen by CBUK Ltd, the contractor responsible for the arch structure, to supply the bearings as housed, sealed units ready for installation. Weighing 3.5 tonnes apiece, the bearings proposed by INA will meet the long-term operating requirements – the life expectancy for the units is 1,000,000 movements and 100 years, with no maintenance requirements!
The design of the arch required bearings with a maximum outside diameter of 1000mm, an inside diameter of at least 300mm and a maximum height of 250mm. In order to absorb thermal expansions and wind movements of the lattice arch the bearings must support maximum swivel movements of +/- 2.5˚ under extreme conditions and +/- 0.7˚ under normal conditions.
A key factor in the bearings ability to meet the tough specification is INA’s ELGOGLIDE low-friction, maintenance-free material. This is a PTFE, commonly known as Teflon, and fabric composite that has been developed by INA to meet the demanding long-term, maintenance-free requirements of the architectural and construction industry.
Furthermore, the low coefficient of friction and lack of stiction – even at extremes of temperature – ensure that structures move freely to take up structural movement caused by temperature fluctuations and wind loadings while, at the same time, minimising the stresses within the structure.
A further advantage of the maintenance-free spherical plain bearings from INA is the reliable “lubrication” in the contact zone even with the most minimal level of swivel motion. Small swivel angles such as these are not possible with conventional spherical plain bearings requiring lubrication with grease or oil, because the swivel motion is not sufficient to form a hydrodynamic film that will reduce friction.
In order to achieve the required life of 100 years and give protection against external influences, the spherical plain bearings were also coated with Corrotect, an extremely thin electroplated protective coating that has proved effective at INA for conventional rolling bearing arrangements over many years.
A further challenge in the bearing design was ensuring the linking of the bearings to the adjacent construction on site. Since the steel arch is assembled while horizontal and only fully erected after completion, the bearings must be fitted in the vertical plane. Axial spherical plain bearings are not self-retaining (the shaft locating washer is loose in the housing washer) so the bearing housing was provided with retaining clamps and transport eyebolts. These clamps are removed before initial use to allow movement of the bearings and the complete arch.
We have a wide range of Wembley installation images available, if you would like a jpg version of these images or would like to look at alternatives please contact Katy Brumwell on 0121 713 3788.
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