Section
10 Pillars and pillar bulkheads
10.1 General
10.1.1 Pillars
are to be arranged to transmit loads from decks and superstructures
into the bottom structure. Pillars are to be constructed out of materials
of adequate compressive strength and modulus, usually steel or aluminium
and these are generally to be of solid, tubular or  beam form. A pillar may be a fabricated trunk or partial
bulkhead.
10.2 Symbols and definitions
10.4 Head and heel connection
10.4.1 The structure
in way of head and heel connections is to be suitably reinforced.
The webs and face reinforcement of such supporting structure are to
be locally increased as necessary with due account being taken of
both the compression and bending moment in way.
10.4.2 Pillars
are to be attached at their heads and heels to plates supported by
efficient brackets. Where the attachment is through bolted, suitable
inserts or compression tubes are to be incorporated within the deck
and hull framing to prevent over-compression and damage to the laminate
in way. Alternatively, tapping plates may be incorporated within the
face reinforcement of the stiffener. Details of the proposed arrangement
are to be indicated on the submitted plans.
10.5 Alignment and arrangement
10.5.1 Pillars
are to be fitted on main structural members. They should be fitted
below deckhouses, windlasses, winches, capstans and elsewhere where
considered necessary.
10.5.2 Wherever
possible, deck pillars are to be fitted in the same vertical line
as pillars above and below, and effective arrangements are to be made
to distribute the load at the heads and heels of all pillars.
10.5.3 Where
pillars support eccentric loads, or are subjected to lateral pressures,
they are to be suitably strengthened for the additional bending moment
imposed upon them.
10.6 Minimum thickness
10.6.2 The minimum
wall thickness of FRP pillars will be specially considered.
10.7 Pillar scantlings
10.7.3 Where
a pillar is of unusual material, the scantlings will be specially
considered.
10.8 Pillars in tanks
10.8.1 Pillars
are in no circumstances to pass through tanks. Where loads are to
be transmitted through the tank, pillars within the tanks are to be
carefully aligned with the external pillars.
10.8.2 Pillars
within tanks are, in general, to be of solid cross section. Proposals
to use hollow section or tubular pillars will be subject to special
consideration and the scantlings as determined from the Rules may
be required to be increased dependent upon the material to be used,
the fluid contained and the arrangement of the pillars. Hollow pillars
are to be adequately drained and vented.
10.8.3 Pillars
within tanks which may be subjected to tensile stresses due to hydrostatic
pressure, are to be designed to provide sufficient connection to withstand
the tension load imposed.
10.9 Pillar bulkheads
10.9.1 Where
the pillar bulkhead is of steel or aluminium construction the method
of attachment to the surrounding structure/framing will be specially
considered.
10.9.2 Where
a pillar bulkhead supports a concentrated load the structure in way
is to be suitably reinforced to distribute the load into the adjacent
stiffening.
10.10 Composite pillars and pillar bulkhead scantlings
10.10.1 The
load P
p, assumed to be carried by a pillar
is to be determined from:
where
|
P
p
|
= |
design load supported by the pillar, which is to be taken as
not less than 5 kN |
|
P
c
|
= |
basic deck girder design pressure as appropriate, plus any other
loadings above the pillar, in kN/m2
|
|
P
a
|
= |
load, in kN, from pillar or pillars above, assumed zero if there
are no pillars over |
|
S
gt
|
= |
spacing, or mean spacing, of girders or transverses, in metres |
|
b
gt
|
= |
distance between centres of two adjacent spans of girders or
transverses supported by the pillars, in metres |
10.10.2 The
load P
b, assumed to be carried by a pillar
bulkhead is to be determined from:
where
|
P
pb
|
= |
design load supported by the stiffener plate combination of
the pillar bulkhead, in kN |
|
P
c
|
= |
basic deck girder design pressure, as appropriate, plus any
other loadings directly above the pillar, in kN/m2
|
|
S
bs
|
= |
spacing, or mean spacing of bulkheads or effective transverses/longitudinal
stiffeners, in metres |
|
b
pb
|
= |
distance between centres of two adjacent spans of girders or
transverses supported by the pillar bulkhead, in metres, and can be
taken as the distance between pillar bulkhead stiffeners where the
stiffener at the top of the bulkhead effectively distributes the load
evenly into the stiffeners |
10.10.3 The
slenderness ratio (
ep/r) of a pillar or plate stiffener
combination is to be determined from:
where
|
r
|
= |
least
radius of gyration of pillar cross section, in cm, |
ep
|
= |
effective
length of pillar, in cm |
E
i, 
i and A
i are as defined
in Pt 8, Ch 3, 1.5 Symbols and definitions 1.5.1.
10.10.4 The
compressive loads P
p or P
pb,
from Pt 8, Ch 3, 10.10 Composite pillars and pillar bulkhead scantlings 10.10.1 and Pt 8, Ch 3, 10.10 Composite pillars and pillar bulkhead scantlings 10.10.2 for pillars and pillar bulkheads
respectively are not to exceed a function of the critical load P
cr, determined from Pt 8, Ch 3, 10.10 Composite pillars and pillar bulkhead scantlings 10.10.5:
where f
p is a factor dependent
upon location and is as indicated in Table 3.10.1 Pillar location factors.
Table 3.10.1 Pillar location factors
| Location
|
f
p
|
| Supporting weatherdeck
|
0,50
|
| Supporting vehicle deck
|
0,25
|
| Supporting passenger deck
|
0,50
|
| Supporting lower/inner deck
|
0,75
|
| Supporting coachroof
|
0,75
|
| Supporting deckhouse top
|
1,00
|
10.10.5 The
critical compressive load, P
cr, for pillars
and plate/stiffener combinations with a slenderness ratio (
e/r) between 75 and 110 may be
determined from:
where
ep
|
= |
effective
span length of pillar or stiffener plate combination, in metres |
|
E
ci
|
= |
compressive modulus of plate laminate, in N/mm2
|
|
k
|
= |
end
fixity factor |
|
|
= |
1,5 for full fixed/bracketed |
|
|
= |
0,75 for partially
fixed |
|
|
= |
0,5 for free ended |
Where the proposed slenderness ratio is below 75 the pillar
will be specially considered. Slenderness ratios in excess of 110
are not to be contemplated.
10.10.7 The
scantlings of wooden pillar bulkheads will be specially considered
on the basis of the Rules. Such pillar bulkheads are to be of equivalent
strength, stiffness and load carrying capability.
10.11 Detail in way of sandwich structure
10.11.1 The
attachment of pillars to sandwich structures should, in general, be
through an area of single skin laminate, see
Pt 8, Ch 2, 4.3 Inserts. Where this is not practicable
and the attachment of the pillar has to be by bolting through a sandwich
structure then a wood, or other suitable solid insert is to be fitted
in the core in way.
10.12 Fire aspects
10.13 Novel features
10.13.1 Where
pillars are of unusual design or constructed from novel material they
will be specially considered in accordance with Pt 8, Ch 3, 2.7 Novel features.
|