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Products and solutions, 2008-01-24, 03:54 PM

"Flyover" at the airport

For the construction of a 200 meter long temporary bridge at Berlin's Tegel Airport, RöRo Shoring Systems have developed a particularly cost-effective solution. With the aid of a special substructure of basic shoring elements, the experts from Wuppertal adapted the standardized bridge elements supplied by the Transportation Ministry to the conditions on site. This dispensed with the need for an expensive custom-built steel structure.

Since Tegel's airport tunnel closed a good year ago for refurbishment, Berliners have been inching their way in infuriating tailbacks along the A111 freeway onto Kurt-Schumacher-Damm. The local public transportation buses, on the other hand, have been bypassing this bottleneck via a purpose-built temporary "flyover" structure (load class 30) that crosses the freeway and the traffic congestion.

This kind of standardized temporary bridge, whose elements are provided by Germany's Federal Transportation Ministry, is known as a "D" bridge. The "D" stands for "Dreieck", the German word for "triangle", and describes the main element of the steel bridge structure. Triangular load-bearing elements are bolted together with walings and straps on the modular principle to yield a load-bearing structure of trusses. Supplemented with standardized carriageway elements, guard rails, crash barriers and optional sidewalks, the outcome is "a road bridge configuration for temporary applications of various kinds".

Normally such temporary bridges are simply mounted on sheet piling boxes or concrete piers constructed on site. However, in Berlin the structure of 13 bridge spans, one- or two-lane, does not have the conventional horizontal configuration, but arches (with a good 5 meters of headroom) over the freeway. The bridge engineers borrowed their strategy for the construction of the arch from shoring construction. For the carriageways, RöRo fabricated special sliding plates out of steel. The shoring experts developed the substructure for the bridge using standard components from their shoring range, i.e. stays, girders, columns etc. If a steel construction firm had custom-built the roughly 100 ton steel bridge substructure, the cost of the steel alone would have sent costs spiraling up. With the method adopted, on the other hand, RöRo was able to offer the contractor Strabag an inexpensive rented solution.

Assembly without traffic holdups

However, it was not the price alone that clinched the contract. Ultimately, it was the overall package of a technically optimal solution, logistical expertise and the assurance that bridge assembly would be handled proficiently and on time under the given difficult conditions (no holdups of air or road traffic). RöRo project manager Reinhold Simons elucidates: "Over a period of about five weeks, six of our steel erectors constructed the bridge and its substructure. All traffic-obstructing tasks were performed at night. During the day we assembled the substructure, and at night the bridge elements were supplied and dropped into place by mobile crane in consultation with the airport control tower." This was of course preceded by finely honed logistical planning, so that the just-in-time deliveries of the various bridge elements slotted in with precision.

Using about 140 different basic elements, the experienced fitters assembled the bridge and tightened some 8,000 bolts – not including the substructure. Buses are now rumbling over the temporary structure – and will continue to do so until summer 2008, because this is how long the refurbishment of the airport tunnel is scheduled to take.

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