STATE OF ART 



Floating and Submerged Concrete Structures 



Concrete production is a world-wide industry using primarily local 

 manpower and materials. Reinforcing and prestressing steels are readily 

 available in all developed countries. 



There is a great deal of long-term experience that started around the 

 1890' s with surface and submerged concrete structures for coastal and 



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harbor facilities, bridge piers, floating structures, and ship hulls i- J 

 In the past 4 years there has been a tremendous surge of development 

 of large concrete structures for use in the open ocean, particularly the 

 North Sea, for offshore oil drilling, production, and storage. 



Concrete structures for coastal protection, dock and harbor works, 

 and large bridge foundations in fresh and salt water are frequently con- 

 structed by combining precasting of large components (floated to the 

 site and submerged) with in-situ concreting underwater by bucket and 

 tremie placement, grout intrusion into prepacked aggregate, and other 

 methods. Representative examples are the San Francisco-Oakland Bay 

 Bridge caisson-piers, the largest of which is 197 feet long, 92 feet 

 wide and over 500 feet high (1930's), the Richmond-San Raphael Bridge 

 "bell piers" (1950's), the Oakland Estuary highway tunnel (early 1960's) 

 and the 3-1/2 mile-long San Francisco Bay Area Rapid 



Transit (BART) Tunnel (late 1960's). Concrete multiple-pontoon floating 

 bridges, each several thousand feet long, have been constructed, two 

 across freshwater Lake Washington and one across saltwater Hood Canal, 

 near Seattle (1940, 1955 and 1961), and one in Tasmania (1940). Precast 

 pontoons, for example 360 feet long, 50 feet wide and 14 feet deep, were 



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