Section
3 Stress control
3.1 General
3.1.1 The nominal
limiting stress requirements for plating and primary and secondary
stiffening members subject to local loading conditions are given in
terms of limiting stress coefficients, see
Table 7.3.1 Limiting stress coefficient for
local loading . The coefficients are expressed
as a proportion of the yield stress of the material.
3.1.3 In the
determination of the magnitude of the equivalent stress, σeq,
it is assumed that the stresses are combined using the following formula:
where
σx
|
= |
direct
stress in the x direction |
σy
|
= |
direct
stress in the y direction |
τ |
= |
shear stress
in the xy plane |
Table 7.3.1 Limiting stress coefficient for
local loading
Item
|
Limiting stress coefficient
|
Bending
|
Shear
|
Equivalent
|
f
σ
|
f
τ
|
f
e
|
Shell envelope:
|
|
|
|
|
(a) Bottom shell plating:
|
|
0,85
|
-
|
-
|
|
|
0,75
|
-
|
-
|
(b) Side shell plating:
|
|
0,85
|
-
|
-
|
|
|
0,75
|
-
|
-
|
(c) Keel
|
|
0,75
|
-
|
-
|
Bottom structure:
|
|
|
|
|
(a) Secondary stiffening:
|
|
0,75
|
0,75
|
-
|
|
|
0,65
|
0,65
|
-
|
(b) Primary girders and web
frames
|
|
0,65
|
0,65
|
0,75
|
(c) Engine girders
|
|
0,55
|
0,55
|
0,75
|
Side structure:
|
|
|
|
|
(a) Secondary stiffening:
|
|
0,75
|
0,75
|
-
|
|
|
0,65
|
0,65
|
-
|
(b) Primary girders and web
frames
|
|
0,65
|
0,65
|
0,75
|
Bow doors:
|
|
|
|
|
(a) Plating
|
|
0,65
|
-
|
-
|
(b) Secondary stiffening
|
|
0,51
|
0,433
|
-
|
(c) Primary stiffening
|
|
0,51
|
0,34
|
0,64
|
Main/strength deck plating and stiffeners:
|
|
|
|
(a) Plating
|
|
0,75
|
-
|
-
|
(b) Secondary stiffening
|
|
0,65
|
0,65
|
-
|
(c) Primary girders and web
frame
|
|
0,65
|
0,65
|
0,75
|
(d) Hatch covers
|
|
0,55
|
0,55
|
0,64
|
Superstructures/deckhouses:
|
|
|
|
(a) Deckhouse front 1st tier:
|
|
0,65
|
-
|
-
|
|
|
0,60
|
0,60
|
-
|
(b) Deckhouse front upper
tiers:
|
|
0,75
|
-
|
-
|
|
|
0,65
|
0,65
|
-
|
(c) Deckhouse aft and sides:
|
|
0,75
|
-
|
-
|
|
|
0,75
|
0,75
|
-
|
(d) Coachroof:
|
|
0,65
|
-
|
-
|
|
|
0,65
|
0,65
|
-
|
(e) House top:
|
|
0,75
|
-
|
-
|
|
|
0,75
|
0,75
|
-
|
(f)
Lower/inner decks and house top subject to personnel loading:
|
|
|
-
|
|
|
0,75
|
-
|
-
|
|
|
0,60
|
0,60
|
-
|
Bulkheads:
|
|
|
|
(a) Watertight bulkhead:
|
|
1,0
|
-
|
-
|
|
|
0,95
|
0,95
|
-
|
|
|
0,90
|
0,90
|
1,0
|
(b) Watertight bulkhead doors
|
|
0,825
|
0,825
|
-
|
(c)
Structure supporting watertight doors
|
0,80
|
0,80
|
-
|
(d) Minor bulkheads:
|
|
0,65
|
-
|
-
|
|
|
0,65
|
0,65
|
-
|
|
|
0,65
|
0,65
|
0,75
|
(e) Deep tank bulkheads:
|
|
0,65
|
-
|
-
|
|
|
0,65
|
0,65
|
-
|
|
|
0,75
|
0,75
|
-
|
Multi-hull cross-deck structure:
|
|
|
|
(a) Plating:
|
|
0,85
|
-
|
-
|
|
|
0,75
|
-
|
-
|
(b) Secondary stiffening:
|
|
0,75
|
0,75
|
-
|
|
|
0,65
|
0,65
|
-
|
(c) Primary stiffening
|
|
0,65
|
0,65
|
0,75
|
Vehicle deck:
|
|
|
|
(a) Plating
|
|
0,6
|
-
|
-
|
(b) Secondary stiffening
|
|
0,425
|
0,425
|
-
|
(c) Primary stiffening
|
|
0,525
|
0,525
|
0,75
|
Helicopter/flight decks:
|
|
|
|
(a) Normal usage:
|
|
0,65
|
-
|
-
|
|
|
0,75
|
0,75
|
-
|
|
|
0,625
|
0,625
|
0,6
|
(b) Emergency landing:
|
|
0,75
|
-
|
-
|
|
|
1,0
|
1,0
|
-
|
|
|
0,825
|
0,825
|
0,9
|
(c) Crane
pedestal/foundation structural elements
|
0,7
|
0,70
|
0,75
|
Table 7.3.2 Limiting stress coefficients for
global loading
Operational mode of craft
|
Limiting stress coefficient
|
Hull girder
|
Cross-deck
|
Bending
|
Shear
|
Equivalent
|
Bending
|
Shear
|
Equivalent
|
f
σgH
|
f
τgH
|
f
σeg
|
f
σgV
|
f
τgV
|
f
σeg
|
Γ ≥ 3,0 or
|
0,80ηHTS
|
0,80ηHTS
|
0,825ηHTS
|
0,80ηHTS
|
0,80ηHTS
|
0,825ηHTS
|
Δ ≤ 0,04(L
R
B)1,5
|
Γ < 3,0 or
|
0,72ηHTS
|
0,72ηHTS
|
0,75ηHTS
|
0,72ηHTS
|
0,72ηHTS
|
0,75ηHTS
|
Δ > 0,04(L
R
B)1,5
|
|
|