(a) Steel renewal is required where the gauged
thickness is less than t
net + 0.5 mm, t
net being the thickness used for the calculation of bending
capacity and shear stresses as given in 4.2 or the local net plate thickness
as given in 4.7. Alternatively,
reinforcing doubling strips may be used providing the net thickness
is not dictated by shear strength requirements for web plates (see 4.5 and 4.6.2) or by local pressure
requirements for web and flange plates (see 4.7).
Where the gauged thickness is within the range t
net + 0.5 mm to t
net + 1.0 mm, coating
(applied in accordance with the coating manufacturer's requirements)
or annual gauging may be adopted as an alternative to steel renewal.
(b) Where steel renewal or reinforcement is required,
a minimum thickness of t
net + 2.5 mm is to
be replenished for the renewed or reinforced parts.
(c) Gussets with shedder plates, extending from
the lower end of corrugations up to 
, or reinforcing doubling strips (on bulkhead corrugations
and stool side plating) are to be fitted when:
where:
|
σ
Ffl
|
= |
minimum upper yield stress, in N/mm2, of the material
used for the corrugation flanges
|
|
σ
Fs
|
= |
minimum upper yield stress, in N/mm2, of the material
used for the lower stool side plating or floors (if no stool is fitted)
|
|
t
fl
|
= |
flange thickness, in mm, which is found to be acceptable on
the basis of the criteria specified in (a) above or, when steel renewal
is required, the replenished thickness according to the criteria specified
in (b) above. The above flange thickness dictated by local pressure
requirements (see 4.7) need not be considered for this purpose |
|
t
st
|
= |
as-built thickness, in mm, of the lower stool side plating or
floors (if no stool is fitted). |
If gusset plates are fitted, the material of such gusset plates
is to be the same as that of the corrugation flanges. The gusset plates
are to be connected to the lower stool shelf plate or inner bottom
(if no lower stool is fitted) by deep-penetration welds (see figure 5).
(d) Where steel renewal is required, the bulkhead
connections to the lower stool shelfplate or inner bottom (if no stool
is fitted) are to be at least made by deep-penetration welds (see figure 5).
(e) Where gusset plates are to be fitted or renewed,
their connections with the corrugations and the lower stool shelf
plate or inner bottom (if no stool is fitted) are to be at least made
by deep-penetration welds (see figure
5).