Gulf Construction Online - Layher keeps rail hub under wraps

Scaffolding & Formwork

Allround scaffolding is playing both an access and support role on the project.

Layher keeps rail hub under wraps

01 December 2002

Layher Allround scaffolding has become established on the market as a synonym for modular scaffolding, says its German manufacturer, which has an active presence in the Middle East. Here, the German scaffolding specialist elaborates on a particularly challenging European project where the system is doing full justice to its reputation as an allrounder.

The Lehrter Bahnhof station in Berlin, currently being built within sight of the German Federal Chancellor's Office, will become the most important railway junctions in Europe.

It is expected that more than 240,000 passengers a day will be using the entire station area on its five traffic levels. While the north-south connection runs about 15 m underground, the east-west routes will be on a gigantic bridge 10 m above the road level.

Modern architecture broke new ground in the design of this station. The Hamburg architect Gerkan, Marg und Partner advocated that the station should complement the overall masterpiece of urban planning and architecture located around the Spreebogen, the bend in the river Spree. That meant there was no chance for the solid and massive bridges made from hollow concrete blocks that are used elsewhere for railways.

The roofing over of the east-west lines was a particular challenge for both the engineers and the structural analysts. The planned design of steel and glass was the result of close cooperation with the Stuttgart-based supporting structure planner Jorg Schlaich.

To assemble the 23 steel arches, also called trusses, over a distance of 321 m (originally the plan even called for 430 m to be roofed), an enormous scaffolding structure was needed and more than 2,000 tonnes of Layher Allround scaffolding was put to use.

To save time, the individual roof segments are not being erected piece by piece, as on a moving construction site, but instead all built at the same time. Around 350,000 cu m of Allround scaffolding are keeping the cast steel truss segments in position, until the elliptical trusses, which in some cases have a span of 67 m, are connected up and are self-supporting. In this way, the Allround system performs two functions at once: firstly, the scaffolding structure acts as a support to absorb heavy loads and to keep components exactly in position, and secondly as an access scaffolding for the 380 workers currently assembling the station roof.

The scaffold itself was put up by erectors, sometimes numbering over 100, from a variety of scaffolding companies (B+P, Allround-Gerustbau and Richter). Since the ground plan of the station is slightly curved over its full length, and is slightly wider in the centre than at the ends, all the trusses differ in length and are at different angles to one another. That demands a high degree of precision on the part of the scaffolders.

It is at this impressive site that the benefits of the Allround scaffolding system are particularly felt. These benefits are the incomparably high assembly speeds achievable, thanks to non-bolted wedge head connections. The freely-settable angles, including the automatically created right angle, help to ensure that the curvatures of the roof can be followed precisely and without problem.

The entire scaffolding is supported on steel beams; the railway operator does not permit its direct mounting on the concrete surfaces of the platforms, as these have already undergone a special surface treatment.

The logistics for the large quantities of scaffolding parts needed also placed heavy demands on all concerned. Precisely-timed deliveries by Layher ensure that shortages never occur and that the necessary material quantities are on hand at all times.

That's what makes Layher - Europe's leading manufacturer in this field - stand out, with a high degree of readiness to deliver even enormous quantities of material in a very short time.

Timing on site is extremely tight. Railway chairman Hartmut Mehdorn has laid down the law and demanded the completion of this central traffic junction before the World Cup in 2006. That's why work on the Lehrter Bahnhof is proceeding round-the-clock, and seven days a week. It's quite a sight to watch how a well-lit site, as long as an aircraft carrier, is additionally lit up at night by the countless flashes from welding equipment.

Incidentally, the new station has a predecessor. A terminus-type station of the same name was built at this spot between 1869 and 1871. The station was badly damaged by bombs in 1943, and its ruins were demolished in 1959. All that was left was a small separate building still used as a stop for Berlin's S-Bahn urban railway.

The modern new glass roof is also felt to be reminiscent of the old station. In those days, the glass roofs were, however, much higher to absorb the steam and smoke of the locomotives. The spatial system of the modern glass roof could not have been planned without the aid of computers. Continually changing angles and curve radii make it necessary for every single one of the 9,200 tinted glass sheets, which are made in Saxony-Anhalt, to be cut to a different size before it is fitted at its precisely defined position.