Hydrodynamic Drag. An analysis of the hydrodynamic drag acting on 
a barge platform must consider three components of drag: (1) form drag, 
(due to separation) (2) wave making drag, and (3) viscous friction drag. 
Accurate estimates of the drag on any but the simplest geometrically 
shaped objects are only possible through the classic procedure of towing 
tests in a suitable model basin. 
Freeboard. An increase in the freeboard will be accomplished by 
an increase in the draft and static instability of the barge. Thus, as 
is generally true for all floating platforms, it is desirable to main- 
tain the freeboard at a minimum height which is commensurate with the 
mission requirements. 
PRELIMINARY DESIGN 
Several candidate platform configurations have been described with 
particular emphasis placed on elevated, semi-submersible and barge 
platforms. Certain design trade-offs possible with each of the leading 
configurations was presented. From the latter, optimization was found 
to depend primarily on considerations of static and dynamic stability, 
material requirements, and design complexity. 
In this section an estimate of candidate platform size, weight, 
and hydrodynamic response will be presented. Size and weight estimates 
will be particularly helpful in estimating the production plant and 
material handling requirements essential for an accurate accounting of 
feasibility and total concept cost. The prediction of hydrodynamic 
response, especially dynamic response in heave, pitch and roll, is an 
important indicator of a candidate's potential for meeting stated 
mission objectives. 
It is emphasized that the platform specifications presented are 
preliminary estimates only. The design calculations were based on 
simplified geometries of each basic configuration as given in Table 3.1. 
Such approximations are sufficiently accurate for relative comparisons 
and determining the order of magnitude of concrete quantities involved. 
Structural Design Assumptions and Criteria 
In addition to the simplified geometric configurations, the follow- 
ing assumptions were applied: 
1. Both the single slab and multi-level decks for the elevated 
and semi-submersible platforms were considered as separate structural 
components resting on buoyant support elements. 
2. The vertical legs for both the elevated and semi-submersi- 
ble platforms were considered to have sufficient lateral bracing to 
prevent failure due to buckling. 
3-18 
