| No ordinary contract |
Demag performs refurbishment on the Tagus bridge in Lisbon
With the refurbishment of six maintenance platforms on the Tagus Bridge in Lisbon, Demag Cranes & Components was awarded an unusual contract by the Koch de Portugal company. The order value for refurbishing maintenance platform no. 3 amounts to Euros 161,000. An option for the conversion of another five platforms in 2004 is an integral part of the contract. Calendar week 43, 2003 is the date scheduled for the erection work to commence, which is expected to last approximately three weeks.
The bridge stretches across the River Tagus linking Alcantara and Almada. It is 2.3 km long and is thus one of the world's largest suspension bridges. With its red supports that tower 190 m above the water, its structure resembles San Francisco's Golden Gate Bridge.
16 or 32 Demag drives are used to move the six maintenance platforms (two of which are 22 m long and 6.4 m wide; the remaining four are 28 x 6.4m), which are suspended underneath the bridge. Each platform travels between two supports. Any necessary maintenance work on the connection elements, the steelwork itself or the paint work, for example, can be carried out regularly and without any difficulty from these platforms, which are situated 70 m above the water level.
The refurbishment order also comprises a completely new electrical system. In this new system, each drive side has its own interconnected control system (inverter control), thus allowing the power demand to be controlled independently. Commands are transmitted to the two drive sides simultaneously. Both control systems are interconnected to check operating parameters such as "ready for operation", or to monitor the output frequency and voltage.
Both the new mechanical wind anchor design, which is specified for a maximum wind speed of 200 km/h, as well as the addition of a new floating bearing suspension arrangement between the platform and bridge structure, are included in the scope of delivery. Unlike the former fixed bearing version, the new design ensures that the platforms will not tilt when maintenance work is being carried out. This is important, since the permissible tolerances for the trolleys would be exceeded due to the interaction of various mechanical and steel components and atmospheric influences, as well as the overall deformation of the bridge caused by the wind and live loads. Any large span deviations in the steelwork are compensated by means of a pendulating (floating bearing) suspension arrangement on one side.
All construction measures will be carried out by the customer. Demag Service personnel will apply their expertise throughout the refurbishment project, right through to the commissioning period. Prior to the contract award, experts from Demag's Service sub-division inspected the maintenance platforms and produced a detailed report containing the scope of refurbishment work to be carried out, as well as a breakdown of the steps to be taken.
This refurbishment contract, which is quite different from the traditional crane business, is a special project for Demag in more than one sense. On the one hand, the project offered the privilege of working on a famous bridge and, on the other hand, provided yet another opportunity to demonstrate the versatility of the After Sales Business Unit of Demag Cranes & Components.
