Movable Bridges Across Shipping Lanes

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	*National Information Service for Earthquake Engineering* *University of California, Berkeley*

Movable bridges are chosen if the density of ship and/or highway or railway traffic does not economically justify the construction of a high-level bridge with long approach ramps.

Movable bridges may be designed as bascule, swing or lift bridges.

GUIABA RIVER AT PORTO ALEGRE, BRAZIL
(1954-60)



	H79. Overall view of lift bridge.


	Total length 777 meters, consisting of approaches with 21.5-meter spans, sidespans of 43 meters and the main bridge, a lift bridge with a span of 55.8 meters. The superstructure of the lift bridge is a steel plate girder with an orthotropic deck and a depth equal to that in the side spans, which gives a pleasing appearance. The box section lift towers are of concrete, hiding and protecting the counterweights and machinery inside, resulting in a smooth appearance. The superstructure of the side spans and approaches were the first prestressed concrete bridges in this area.

Preliminary design and final structural design. Construction engineering.

References:

Leonhardt, F., and Andrä, W.: “Die Guaiba Brücke bei Porto Alegre, Brasilien (The Guaiba Bridge at Porto Alegre, Brazil),” Beton- und Stahlbetonbau 58 (1963), pp 273-279.

Mörsch, E.: Brücken aus Stahlbeton und Spannbeton, 6. Auflage, neu bearbeitet von F. Leonhardt (Bridges of Reinforced and Prestressed Concrete, 6th Edition by F. Leonhardt). Verlag Konrad Wittwer, Stuttgart, 1958, pp 128-131.

BRIDGE ACROSS SHATT-AL-ARAB, IRAQ
(1972-78)



	H80. Overall view of swing bridge.


	The bridges across the Shatt-al-Arab at Basrah have a total length of 331.75 plus 430.15 meters and normal spans of 46.9 meters. The center section of the smaller bridge is a swing bridge with cantilever lengths of 33.5 meters. Deck width 21 meters. The superstructure of the entire bridge is a prestressed concrete box girder. The weight of the swing bridge, 3500 tons, makes it the heaviest of its kind in the world. Foundation of all piers on large diameter bore piles. The superstructure of both bridges, including the swing bridge, was built by incremental launching from one abutment to the other. After reaching the final position, the tendons at the joints at both ends of the swing bridge were released and removed.

Tender design and tender documents, final design.

Ref: Seifried, G. and Wittfoht, H.: “Die Brücke über den Shatt-al-Arab in Basrah, Irak (The Bridge across the Shatt-al-Arab at Basrah, Iraq),” Beton- und Stahlbetonbau 74 (1979), pp 77-85.


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	The University of California, Berkeley Copyright 1997, The Regents of the University of California. Structural Engineering Slide Library, W. G. Godden, Editor Set H: Structures of Leonhardt, Andrä and Partners


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