Table 1. Typical Simplified Geometry Used in Preliminary 
Design Calculations 
Solid, two way slab structurally adequate to 
span spacing between supports. 
Three deck levels consisting of flight deck 
plus two lower-level decks with 20-ft clearance 
for middle deck and 8-ft clearance for bottom 
deck. 
Barge-type hull 100-ft beam with 50-ft clear span between hulls; 
U-shaped cross section. 
Elevated platform columns 25-ft diameter, cylindrical, spaced at 50-ft 
or legs and 43-ft centers each way respectively for 
the single and multi-level decks. 
Semi-submersible with 36-ft | 26-ft diameter, cylindrical columns, spaced as 
diameter hulls and column for the elevated platform, atop horizontal 
supports cylindrical hulls transversely spaced to match 
50-ft or 43-ft spacing of columns. 
> : 
Selected spacing was for purpose of maintaining same draft for the single 
and multi-level decked platforms. 
Results The principal difference lies in the draft for each 
candidate, the elevated platform having a loaded 
Size and Weight. Preliminary design specifi- draft more than five times that of the barge. 
cations for five types of the 1000x4000-ft platforms 
are presented in Table 2. 
Table 2. Preliminary Design Weights (LT) for 
the 1000x4000-ft Platforms 
Preece | 
Type Concrete Conc. | Water | Total 
3,250 1,010 | 2,400 | 6,660 
5,060 1,470 | 2,860 | 9,390 
- Single deck 2,500 590 | 1,130 | 4,270 
- Multi-deck 3,760 380 | 1,420 | 5,560 
The tabulations for the columnar platform and 
the semi-submersible platform are given for both 
single and multiple decks. These values represent 
the extremes, since in all probability the 
optimized designs for specific missions will have 
combinations of single and mltiple decks; the 
weights of such platforms will lie between these 
extremes. The barge-hull platform has interior 
decks; the single deck did not appear practical 
for structural reasons. Thus, only one tabulation 
for the barge is given. Figure 3. Elevation views of the three MOBS 
base concepts. 
Columar 
Single deck 
Multi-deck 
Semi-Submersible 
Figure 3 illustrates the relative size of the 
three MOBS base concepts while the freeboard and 
plan dimensions are identical for each platform. 
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