StorstrÆm Bridge
Denmark, 1933-1937

De Danske Statsbaner (The Danish State Railways).
Designed by
The Danish State Railways and Christiani & Nielsen A/S, Copenhagen (piers only).

Constructed by
Dorman Long and Co. Ltd. and Christiani & Nielsen A/S, Copenhagen.
Technical Data
The work consists of two bridges, namely the Masnedsund Bridge and the Storstr?m Bridge. The former is a bascule bridge with a total length of 200 m (656 ft.) between the abutments and carries a single railway track, a 5.6 m (18 ft. 4 in.) wide roadway, and a 2.5 m (8 ft. 2 in.) wide footway.
The Storstr?m Bridge has a length of 3,200 m (10,500 ft.) between the abutments and carries the same railway track, roadway and footway as the Masnedsund Bridge.
The Storstr?m and Masnedsund Bridges connect the island of Zealand with the island of Falster, and replace the former ferry connection. The traffic flow from Scandinavia to the southern continent is thereby improved considerably.
The contract for these bridges was signed on 13th May, 1933, between the Danish State Railways and the English firm of Dorman Long and Co. Ltd., with Messrs.
Christiani & Nielsen acting as sub-contrac-tors for all foundation work and for the reinforced concrete sections of the superstructure, such as roadway slabs and ballast boxes. The Bridge was handed over to the Client and opened to traffic on 26th September, 1937.
Type of Construction
The Masnedsund Bridge is supported on two abutments and five piers, one of which contains the machinery for the bascule bridge. All the piers were constructed inside steel cofferdams. After underwater excavation, an underwater concrete slab was cast, the cofferdam was dewatered and the piers were constructed in the ordinary way.The two abutments and one of the piers are founded on wooden piles, while all other piers are founded directly on the ground.

The StorstrÆm Bridge is supported on two abutments and 49 piers.All the piers except one are founded directly on the bottom. For the exception, the bottom is strengthened by wooden piles. Maximum water depth is 13.8 m (45 ft.). Eight of the piers were constructed in the ordinary way inside a steel cofferdam, although in some cases it was necessary to cast an underwater foundation slab before dewatering the cofferdam. The remaining 41 piers were constructed in a special way, by means of so-called "Units". These units were double-walled elliptical shaped steel cofferdams, which were able to float, and which acted as scaffolding, as a guide for driving and supporting the steel sheet piles, and as formwork for the lower part of the concrete in the foundations. Due to soil conditions two types of units had to be used. The first was used where the steel sheet piles were driven outside the unit; that is, where the soil was strong enough to resist the outside water pressure when the cofferdam was dewatered, and the other was used where the soil was too weak to withstand the outside water pressure. In the latter case the steel sheet piles were driven inside the unit, and the excavation and casting of the lower part of the foundation were done as underwater work. The foundation blocks were cast at level -3.00 m (-9 ft. 10 in.), inside the units after which water was let into the cofferdam.
The cofferdam was then emptied of ballast water and floated free of the foundation block. The part of the pier between levels -3.00 m (-9 ft.10 in.) and+3.00 m (+9 ft. 10 in.) consists of a granite-clad reinforced concrete shell cast on a slipway and floated into place by two barges. The shell was pumped empty and filled with concrete. The piers shafts are hollow and were cast inside sliding steel forms. The maximum height of the piers is 38.2 m (125 ft.).
No special problems were encountered in the construction of the roadway slabs and the ballast boxes.
"Civil Engineering", August 1935, pp. 232-248, and September, 1937, pp. 319-327. "Zentralblatt der Bauverwaltung", October, 1936. "Compressed Air Magazine", May, 1937. "The Structural Engineer", February, 1939. "Engineering News Record", 6th July, 1939, pp. 47-49. "La Technique des Travaux", Liege, June, 1936, pp. 380-386.