Section
3 Local hull loads and strength
3.1 Impact loads on the bottom and side shell
3.1.2 The distributed pressure, p
dist, along the length of the bottom structure is taken as 0,44 times the
peak pressure, ppeak.
3.1.3 The peak pressure, p
peak, is generally to be applied to plating and secondary stiffeners. The
distributed pressure p
dist, is generally to be applied to primary frames, girders and large
unstiffened panels of plating, and over an impact area, Aw,i, taken
as:
where
Fw,i is defined in Ch 3, 2.3 Structural response to wave impact 2.3.2.
3.1.4 Both the
peak pressure and distributed pressure are to be applied to the bottom
structure to the transverse extent of the outermost chine. Above this
point both pressures may be reduced linearly to pressure, p
gun, at the gunwale.
|
p
gun
|
= |
 kN/m2
|
where
|
K
3
|
= |
 – 0,5 for x/L > 0,75
|
|
x
|
= |
distance
from aft end to the point at which K
3 is required,
in metres
|
L is defined in Ch 1, 1.2 Definitions and symbols
a
v,i is defined
in Ch 3, 2.2 Acceleration due to wave impact 2.2.2 for the longitudinal centre
of gravity impact case and is not to be taken less than 1,0.
3.2 Floating loads
3.3 Deck loads
3.4 Machinery loads
3.4.1 Machinery
foundation reactions resulting from collision accelerations, torque
and dynamic loads are to be provided by the designer.
3.5 Slinging and jacking loads
3.5.1 The supporting
structure, such as lifting posts and struts, is to be designed to
carry the slinging and jacking loads at each lifting point and is
to have adequate buckling capacity to withstand the concentrated loads.
Allowance is to be made for the inclination of any lifting wires which
may give rise to longitudinal, transverse and vertical loads.
3.6 Collision loads
3.6.1 The strength of supporting structure and attachments of masses greater than
50 kg are to be able to withstand design accelerations without fracturing. Force
magnitudes and directions are to be taken as follows:
- 6g forward direction.
- 3g after direction.
- 3g transverse direction.
- 3g vertical upward direction.
- 4g vertical downward direction.
The vertical acceleration cases include the self-weight component.
3.7 Local strength
3.7.1 When applying the loads given in this Section, strength models based on simple plate
bending, beam theory, or other recognised methods will generally be acceptable. Where
longitudinal and transverse stiffeners form grillage structures providing mutual
support, or where the structural arrangement is complex, finite element or alternative
methods may have to be used and are to be agreed with LR prior to submission.
Consideration is to be given to assumptions regarding end fixity and load application as
appropriate for the selected method.
3.7.2 Laterally
loaded thin skins designed to support the design pressure by membrane
action with associated large deflections will be specially considered, see also 2.7.5. For guidance, the thickness of thin skins, t
skin, may be derived as follows:
|
t
skin
|
= |
 mm
|
3.7.3 where
|
p
|
= |
design
pressure, in kN/m2
|
|
a
|
= |
longest
dimension of the skin, in m |
|
b
|
= |
shortest
dimension of the skin, in m |
|
σa
|
= |
0,2
per cent proof stress of the aluminium, in N/mm2
|
|
η |
= |
0,0085α2 – 0,1025 α + 0,5
|
|
E
|
= |
modulus
of elasticity, in N/mm2
|
3.7.4 Structural
geometry is to be arranged and detailed to ensure a smooth transfer
of loads throughout the structure. Concentrated or point loads are
to be transmitted into the supporting structure by a series of stiff
supporting members. In no case are concentrated or point loads to
land on unsupported plating.
3.7.5 The longitudinal
girders forming the machinery foundations are to extend as far forward
and aft as practicable and be adequately supported by transverse primary
structure.
3.7.6 Integration
of lift fans and associated supporting structure will be specially
considered.
3.7.7 In areas
where fluctuating pressure (panting) occurs e.g. fan bays, inlets,
volutes etc. design details will be specially considered.
3.7.8 Openings
in the structure are to be suitably framed and have well-rounded corners
to minimise stress concentrations.
|
| Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime
and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective
officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications
Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance
on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant
Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is
exclusively on the terms and conditions set out in that contract.
|
 |
|