By using its expertise and experience as early as possible in the design stages of large engineering projects, a bearing supplier can help the architect to select the most appropriate, cost effective bearing solution.
The design of bearings for large structures and buildings such as sports stadiums, bridges, dams, flood gates, train station roofs and airports, is critical and must not be treated as an afterthought by architects and designers. Typically these bearings have to support several hundred tonnes in weight and be able to cope with often harsh operating environments, including extreme heat, freezing temperatures, sandstorms and aggressive saltwater. In certain applications, the bearings may also need to be earthquake-proof.
It is important that designers engage with the bearing supplier as early in their design process as possible, so that the design of the bearing can be optimised for the application, saving time and money and usually resulting in a more cost effective overall design of a building or structure.
Dr Steve Lacey, Engineering Manager at Schaeffler (UK) Ltd comments: “Bearings are often taken for granted, even though they are critical to the performance of the building or structure. If the architect or main contractor on the project engages with the bearing supplier early in the design process, advice and guidance can be provided on the most appropriate bearing solution for the application. This can save major costs for the contractor in terms of redesign or modification work later on.”
“The surrounding structure can influence the behaviour of the bearing and so it is critical that the selection of the bearing is correct. Of course, the larger the bearing and the surrounding structure, the higher the project risk if the bearing selection is not taken seriously.”
When sourcing bearings for these types of structures, architects need to consider various bearing design criteria, including load ratings, operational safety, the life rating of the bearing and the lifecycle cost of the bearing (including maintenance and servicing costs). The bearing supplier can use its expertise and experience to help the architect select the most appropriate, cost effective bearing solution.
The bearings themselves – which might be spherical plain bearings, cylindrical bushings, rod ends or combination bearings – should be maintenance-free if possible. A bascule bridge, for example, has little time set aside for maintenance work to be carried out, particularly if the bridge is a major traffic route through a city and has to open and close several times a day to enable ships to pass through.
Take the Barcelona Harbour Bridge in Spain, for example, which uses maintenance-free ELGOGLIDE plain bearings from Schaeffler in each of its moveable bridge sections. These low friction, dry-running, high load capacity bearings support each of the bridge sections, which weigh around 2,000 tonnes and are 70 metres in length. ELGOGLIDE bearings are ideal for supporting oscillating motion, as their dynamic load ratings are very high relative to their weight.
ELGOGLIDE is a PTFE fabric that consists of Teflon and support fibres, as well as a resin matrix and adhesive on the steel support body. The result is a balanced combination of high load capacity, excellent wear and friction behaviour and excellent dry-running characteristics.
Schaeffler’s ELGOGLIDE bearings are also being used in other types of bridge, including balance, suspension, swing, vertical lift and hydraulic bridges. In the UK for example, Schaeffler supplied the main pivot bearing assembly on the swing bridge at Preston Docks. The bearing assembly comprises a spherical plain thrust bearing, used as the main pivot, complete with a steel fabricated housing for the bearing, including seals and attachments to couple with the hydraulic actuators.
The bearing has to withstand a thrust force of 9,250kN and must rotate through an arc of 55 degrees when the bridge is opened. The housing also has to withstand wind forces of up to 150kN, as well as an emergency lateral force of 1,200kN, without damage. The bearing assembly requires no maintenance as it operates without the need for any lubrication and is a genuine ‘fit-and-forget’ solution for Preston City Council.
Other prestigious building projects in the UK include Wimbledon Centre Court, where more than 300 spherical roller bearings from Schaeffler are support the new retractable roof. The London Eye, Wembley Stadium and Lloyds Bank in London are other buildings supported by Schaeffler’s bearings.
Open the flood gates
Schaeffler is also involved in several high profile dam construction projects around the world. Many of these dams have flood gates that require bearings to support the movement of the locks at low sliding speeds, even in extreme temperatures and harsh weather conditions.
The flood gates in the Saemangum dam in Korea, for example, are 15 metres high and have a width of 30 metres. These locks include segment, inlet and radial flood gates or check gates, each of which is supported by Schaeffler’s ELGES spherical plain bearings.
Whenever concrete and steel meet, inevitably there will be some sort of foundation settling, manufacturing accuracies will increase and elastic deformations and changes in length will occur as a result of temperature changes. Water pressure and the weight of the lock act as a single direction load on spherical plain bearings. It is almost impossible for a lubricating film to be formed in the load zone, especially after extensive downtimes.
The performance of the ELGES range of spherical plain bearings has now been improved. The ‘X-Life’ premium quality seal of approval represents a 50 per cent improvement in static load ratings and a potential service life of up to eight times higher than competing bearing products. The ELGOGLIDE coating given to the bearings is completely resistant to moisture, making the bearings suitable for hydraulic steel structures. X-Life large spherical plain bearings are available with shaft diameters that start from 320mm (radial) and 220mm (thrust).
For more information on Schaeffler’s range of bearings for buildings and structures, please visit www.schaeffler.co.uk or contact the marketing department on info.uk@schaeffler.com and ask for a copy of the PBW brochure.
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