Figure 8. 
Launching of model platform. 
Tests 
Testing of the model was not completed at this 
writing. Results of preliminary tests indicate 
that a full-scale structure in the unballasted 
state will have the following natural periods: 
heave - greater than 20 seconds 
pitch and roll - greater than 25 seconds 
After nine months of submergence, the hulls were 
dry on the inside with no trace of leakage or 
permeating seawater. 
Conclusions 
It was concluded from the study that concrete 
is a feasible and practical construction material 
for large ocean platforms. It seems clear that 
existing construction technology can be successfully 
applied to the fabrication through an orderly pro- 
cess of development. Raw material quantities, even 
for the largest platform studied at 34 million 
cubic yards, are not excessive. Cement requirement 
is nominally 7 million barrels, less than 2% of the 
1968 production of 400 million barrels. Also, the 
aggregate production of one million tons per year 
can be readily accomplished. The successful 
construction and launch of a 1/10 scale concrete 
platform supports the conclusion that neither the 
size nor shape of the components presents unusual 
construction requirements. The experience gained 
in the concrete ship building program is also 
indicative of the suitability of applying tried 
and proven techniques to the construction of con- 
crete vessels. The success of these vessels, com- 
bined with substantial progress in concrete 
techniques during the intervening years, offers 
assurance that the structures under study can be 
built. It appears likely that the final selection 
of a platform will be more dependent upon stability, 
ease of assembly, station-keeping, and other factors 
related to design and cost rather than to feasibil- 
ity vis-a-vis the state-of-the-art in concrete 
construction. 
References 
1. Hromadik, J. J., et. al. (1971), "Mobile Ocean 
Basing Systems - A Concrete Concept," Naval Civil 
Engineering Laboratory, Technical Note N-1144. 
Port Hueneme, California, January 1971. 
2. Davis, D. A. (1973), "Mobile Ocean Basing 
Systems - The Concrete Semi-Submersible Platform," 
Naval Civil Engineering Laboratory, Technical Note 
N- » Port Hueneme, California. (in preparation) 
3. Engineering News-Record (1946), "Army Engineer- 
ing Finish Successful Tests of Floating Seadrome 
Model Design," Vol. 131, No. 13, March 28, 1946, 
p- 449. 
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