A 300 x 300-foot barge MOBS can be constructed which has a consid- 
erable degree of positive static stability without the need of ballast, 
whereas the semi-submersible and elevated platforms must be ballasted 
to prevent capsizing. 
The barge platform hull can be used for storing and housing 
personnel and equipment, including power plants and propulsion systems. 
The shallow draft of the barge, and the use of fairings fore and 
aft, will result in a comparatively low hydrodynamic drag. This becomes 
an important consideration if the platform must be moved rapidly, or 
for appreciable distances. The shallow draft will aiso allow operations 
at near-shore sites that are not possible with deeper draft configurations. 
The barge may also be an effective breakwater. It has been demon- 
strated, both analytically and experimentally, that a large, floating 
slab is an effective wave attenuator. It has been reported (Bureau of 
Yards and Docks, 1963) that the transfer coefficient (ratio of transmitted 
wave height to incident wave height) for a rigid, floating slab, in deep 
water with zero draft, is about 0.2 for a ratio of slab length to incid- 
ent wave length of 1.0. Thus, by assuming that a flat bottom barge be- 
haves as a rigid slab, a moored barge with plan dimensions of 1,200 x 
400-feet could be expected to attenuate 1,200-foot by 400-foot long 
waves by 80%, depending upon the alignment of the longitudinal axis of 
the barge. This is tantamount to a 96% reduction in the transmitted 
wave energy. One can conceive a sheltered area in the lee of the plat- 
form which could be used for docking all types of vessels, large and 
small. The relative motion between the barge-type platform and the 
vessels would be minimal and, as a result, cargo could be easily 
transferred. 
Disadvantages. Compared to a 300-foot x 300-foot elevated platform, 
a barge platform of the same size will tend to respond more readily to 
the seaway. Helicopters can tolerate some deck movement - operation 
from aircraft carriers are routine - and future VIOL aircraft may event- 
ually achieve a similar tolerance to deck movement. It is questionable, 
therefore, whether the stability afforded by a semi-submersible or an 
elevated platform is really necessary for operations envolving these 
types of aircraft. 
The barge platform is susceptible to two loading conditions which 
are of lesser importance for elevated and semi-submersible platforms. 
Firstly, hogging and sagging stresses must be considered due to the 
shallower height of the barge and greater water plane area. In all 
likelihood, the stresses induced by hogging and sagging can be accom- 
modated by judicious use of longitudinal prestressed structural elements, 
especially at the barge mid-point. 
Barge Configurations. Figure 3.3 illustrates three possible barge 
hulls. The first, the simplest configuration geometrically, is a flat 
sided, flat bottom hull having the distinction of offering the lowest 
draft to displacement ratio. Although catamaran and trimaran hulls will 
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