A Solution to the Inherent List on Nimitz Class Aircraft Carriers

Stress Calculations: Stiffening
k = coefficient that depends on <strong>the</strong> plate edge conditions,
aspect ratio (AR) of <strong>the</strong> panel, and position of point being considered
a := kP, new
p = pressure based on 50 I<strong>to</strong>ns of ballast addition
b = panel width
a = panel length
t = plate thickness
k . , _^ j •= 7' k_i j •= .5 k values are most conservative
Nimply_supported • ■'- "^jlamped
a .- 20ft b :- 24ir based on adding a stiffener down <strong>the</strong> nviddle of <strong>the</strong> deck
Pnew = 12.388^ t := .5in
in
lb
a
max_allowable
II ui = 28
-^"'""^
000—
^
lAW with <strong>the</strong> General Specs
t-
(Section
v
100)
^
in
^simply_supported • 'Simply_supported '^newl ^
^simply_supported = 21407—
. 2
in
^clamped • Clamped newl ^
clamped 14271 lb
m
Maximum Allowable Stress for OS is 28,000 psi. By adding stiffeners at 24 in AND with <strong>the</strong> addition of less ballast, <strong>the</strong> stress
falls below that of simply supported and that of clamped. Simply supported and clamped structural cases are idealizations of
structural member support illustrating zero stiffness and infinite stiffness, nei<strong>the</strong>r of which exists in any real-world structural
system. On board ship, structural systems can be conveniently approximated by one or <strong>the</strong> o<strong>the</strong>r case, but in fact have stiffness
between one or <strong>the</strong> o<strong>the</strong>r. Navy structural analysis is based off clamped ends, <strong>the</strong>refore <strong>the</strong> stress should be well below
maximum allowable. As mentioned previously, however, adding ballast <strong>to</strong> <strong>the</strong> 4th deck is not feasible due <strong>to</strong> <strong>the</strong> inability <strong>to</strong>
stiffen <strong>the</strong> 4th deck.
^clamped
^max_allowabl(
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