Section
10 Pillars and pillar bulkheads
10.1 Application
10.1.1 Pillars
are to be arranged to transmit loads from decks and superstructures
into the bottom structure. Pillars are generally to be constructed
from solid, tubular, or I beam section. A pillar may
be a fabricated trunk or partial bulkhead.
10.2 Determination of span length
10.2.1 The effective span length of the pillar, lep, is in
general the distance between the head and heel of the pillar. Where substantial brackets
are fitted, lep may be reduced by 2/3 the depth of the bracket at each
end.
10.3 Head and heel connections
10.3.1 Pillars
are to be attached at their heads to plates supported by efficient
brackets, in order to transmit the load effectively. Doubling or insert
plates are to be fitted to decks under large pillars and to the inner
bottom under the heels of tubular or hollow square pillars. The pillars
are to have a bearing fit and are to be attached to the head and heel
plates by continuous welding. At the heads and heels of pillars built
of rolled sections, the load is to be well distributed by means of
longitudinal and transverse brackets.
10.4 Alignment and arrangement
10.4.1 Pillars
are to be located on main structural members. They are in general
to be fitted below windlasses, winches, capstans, the corners of deckhouses
and elsewhere where considered necessary.
10.4.2 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.
10.4.3 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.
10.4.4 Doublers
are generally to be fitted on decks and inner bottoms, other than
within tanks where doublers are not allowed. Brackets may be used
instead of doublers.
10.5 Minimum thickness
10.5.1 The minimum
wall thickness of hollow pillars is to be taken as not less than 1/20
of the external dimension of the pillar.
10.6 Design loads
10.6.1 The design
loading, P
p, to be used in the determination
of pillar scantlings is as follows:
where
|
P
p
|
= |
design load supported by the pillar, to be taken as not less
than 5 kN |
|
P
c
|
= |
basic deck girder design pressure, as appropriate, plus any
other loadings directly 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 pillar, in metres |
10.7 Scantlings determination
10.7.1 The cross-sectional
area of the pillar, A
p, is not to be less
than:
where
|
f
p
|
= |
pillar location factor defined in Table 3.10.1 Pillar location factors
|
|
σs
|
= |
specified
minimum yield strength of the material, in N/mm2
|
|
k
f
|
= |
pillar end fixity factor |
|
|
= |
0,25 for full fixed/bracketed |
|
|
= |
0,50 for partially
fixed |
|
|
= |
1,0 for free ended |
|
r
|
= |
least
radius of gyration of pillar cross-section, in cm |
| = |
|
p
|
= |
least moment
of inertia of cross-section of pillar or stiffener/plate combination,
in cm4
|
ep
|
= |
effective
span of pillar, in metres, or bulkhead as defined in Pt 6, Ch 3, 10.2 Determination of span length.
|
Table 3.10.1 Pillar location factors
| Location
|
f
p
|
| Supporting
weather deck
|
0,50
|
| Supporting
vehicle deck
|
0,50
|
| Supporting
passenger deck
|
0,50
|
| Supporting
lower/inner deck
|
0,75
|
| Supporting
coachroof
|
0,75
|
| Supporting deckhouse
top
|
1,00
|
10.9 Pillars in tanks
10.9.1 In no
circumstances are pillars to pass through tanks. Where loads are to
be transmitted through tanks, pillars within the tanks are to be carefully
aligned with the external pillars.
10.9.2 Pillars
within tanks are, in general, to be of solid cross section. Where
it is proposed to use hollow section pillars each case will be subject
to special consideration and the scantlings as determined from the
Rules may require 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.
10.9.3 Where
pillars within tanks may be subjected to tensile stresses due to hydrostatic
pressure, the design is to provide sufficient welding to withstand
the tensile load imposed.
10.9.4 Doubling
plates at ends of pillars within tanks are not acceptable.
10.10 Pillar bulkheads
10.10.1 The
stiffener/plate combination used in the determination of pillar bulkhead
scantlings is to be that of a stiffener with an effective width of
attached plating as determined from Pt 6, Ch 3, 1.11 Other materials.
10.10.2 The
cross-sectional area of the pillar bulkhead, A
pb,
is to be determined in accordance with Pt 6, Ch 3, 10.7 Scantlings determination using
the design loading, P
pb, as follows:
where
|
P
pb
|
= |
design load supported by the stiffener plate combination of
the pillar bulkhead |
|
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
stiffeners at the top of the bulkhead effectively distributes the
load evenly into the stiffeners |
10.10.3 The
thickness of the bulkhead plating is in no case to be taken as less
than 4 mm.
10.11 Direct calculations
10.11.1 As
an alternative to Pt 6, Ch 3, 10.6 Design loads, pillars
may be designed on the basis of direct calculation. The method adopted
and the stress levels proposed for the material of construction are
to be submitted together with the calculations for consideration.
10.12 Fire aspects
10.12.1 Pillars
and pillar bulkheads are to be suitably protected against fire, and,
where necessary, be self-extinguishing or capable of resisting fire
damage. All pillars are to comply with the requirements of Pt 17 Fire Protection, Detection and Extinction.
10.13 Novel features
10.13.1 Where
unusual or novel pillar designs are proposed that are unable to comply
with the requirements of this Section, their design together with
the direct calculations are to be submitted for special consideration.
|