5. MONITORATGE AMB IOT
5.3 Protocols de comunicació IoT
1.1 Frame spacing
Forward of the collision bulkhead and aft of the after peak bulkhead, the frame spacing shall in general not exceed 600 mm.
1.2 Definitions
k = material factor according to Section 2, B.2.
R = unsupported span [m] according to Section 3, C., see also Fig. 9.1
Rmin = 2,0 m
RKu, RKo = length of lower/upper bracket connection of main frames within the length R [m], see Fig. 9.1
Fig. 9.1 - Unsupported span of transverse frames
ma =
e = spacing of web frames [m]
p = ps or pe as the case may be
ps = load on ship's sides [kN/m2] according to Section 4, B.2.1
pe = load on bow structures [kN/m2] according to Section 4, B.2.2 or stern structures according to Section 4, B.2.3 as the case may be
pL = 'tween deck load [kN/m2] according to Section.4, C.1.
p1, p2 = pressure [kN/m2] according to Section 4, D.1.
Hu = depth up to the lowest deck [m]
cr = factor for curved frames
= crmin= 0,75
s = max. height of curve.
2. Main frames
2.1 Scantlings
2.1.1 The section modulus WR and shear area AR of the main frames including end attachments are not to be less than:
WR = [cm3]
upper end shear area :
ARO = [cm2]
lower end shear area :
ARU = [cm2]
n = 0,9 ! 0,0035 @ L for L < 100 m
= 0,55 for L 100 m
c =
cmin = 0,6
Within the lower bracket connection the section modulus is not to be less than the value obtained for c = 1,0.
2.1.2 In ships with more than 3 decks the main frames are to extend at least to the deck above the lowest deck.
2.1.3 The scantlings of the main frames are not to be less than those of the 'tween deck frames above.
2.1.4 Where the scantlings of the main frames are determined by strength calculations, the following permissible stresses are to be observed:
bending stress: Fb = [N/mm2]
shear stress: J = [N/mm2]
equivalent stress: Fv = [N/mm2]
2.1.5 Forces due to lashing arrangements acting on frames are to be considered when determining the scantlings of the frames (see also Section 21, H)
2.1.6 For main frames in holds of bulk carriers see also Section 23, B.5.2.
2.2 Frames in tanks
The section modulus W and shear area A of frames in tanks or in hold spaces for ballast water are not to be less than the greater of the following values :
W1 = n @ c @ a @ R2 @ p1 @ cr @ k [cm3] W2 according to Section 12, B.3.1, and
A1 = (1 - 0,817 @ ma) 0,05 @ a @ R @ p1 @ k [cm2] A2 = (1 - 0,817 @ ma) 0,04 @ a @ R @ p2 @ k [cm2] n and c see 2.1.1.
2.3 End attachment
2.3.1 The lower bracket attachment to the bottom structure is to be determined according to Section 3, D.2. on the basis of the main frame section modulus.
2.3.2 The upper bracket attachment to the deck structure and/or to the 'tween deck frames is to be determined according to Section 3, D .2. on the basis of the section modulus of the deck beams or 'tween deck frames whichever is the greater.
2.3.3 Where frames are supported by a longitudinally framed deck, the frames fitted between web frames are to be connected to the adjacent longitudinals by brackets. The scantlings of the brackets are to be determined in accordance with Section 3, D.2. on the basis of the section modulus of the frames.
3. 'Tween deck and superstructure frames 3.1 General
In ships having a speed exceeding v0 = 1,6 [kn], the forecastle frames forward of 0,1 L from F.P are to have at least the same scantlings as the frames located between the first and the second deck.
Where further superstructures, or big deckhouses are arranged on the superstructures strengthening of the frames of the space below may be required.
For 'tween deck frames in tanks, the requirements for the section moduli W1 and W2 according to 2.2 are to be observed.
3.2 Scantlings
The section modulus Wt and shear area At of the ’tween deck and superstructure frames are not to be less than:
Wt = 0,55 @ a @ R2 @ p @ cr @ k [cm3] At = (1 - 0,817 @ ma) 0,05 @ a @ R @ p @ k [cm2] p is not to be taken less than:
pmin = 0,4 @ pL @ [kN/m2]
b = unsupported span of the deck beam below the respective 'tween deck frame [m].
For 'tween deck frames connected at their lower ends to the deck transverses, pmin, is to be multiplied by the factor : f1 = 0,75 + 0,2 1,0
3.3 End attachment
'Tween deck and superstructure frames are to be connected to the main frames below, or to the deck. The end attachment may be carried out in accordance with Fig. 9.2.
For 'tween deck and superstructure frames 2.3.3 is to be observed, where applicable.
Fig 9.2 - Typical ends attachments of tween deck and superstructure frames 4. Peak frames and frames in way of the stern
4.1 Peak frames
4.1.1 Section modulus WP and shear area AP of the peak frames are not to be less than:
WP = 0,55 @ a @ R2 @ p @ cr @ k [cm3] AP = (1 - 0,817 @ ma) 0,05 @ a A R @ p @ k [cm2]
4.1.2 Where the length of the forepeak does not exceed 0,06 L the section modulus required at half forepeak length may be maintained throughout the entire forepeak.
4.1.3 The peak frames are to be connected to the stringer plates to ensure sufficient transmission of shear forces.
4.1.4 Ships not exceeding 30 m in length are to have peak frames having the same section modulus as the main frames.
4.1.5 Where peaks are to be used as tanks, the section modulus of the peak frames is not to be less than required by Section 12, B.3.1 for W2.
4.2 Frames in way of the stern
4.2.1 The frames in way of the cruiser stern arranged at changing angles to the transverse direction are to have a spacing not exceeding 600 mm and are to extend up to the deck above peak tank top maintaining the scantlings of the peak frames.
4.2.2 An additional stringer may be required in the after ship outside the afterpeak where frames are inclined considerably and not fitted vertically to the shell.
5. Strengthenings in fore- and aft body
5.1 General
In the fore body, i.e. from the forward end to 0,15 L behind F.P., flanged brackets have to be used in principle.
As far as practicable and possible, tiers of beams or web frames and stringers are to be fitted in the fore- and after peak.
5.2 Tiers of beams
5.2.1 Forward of the collision bulkhead, tiers of beams (beams at every other frame) generally spaced not more than 2,6 m apart, measured vertically, are to be arranged below the lowest deck within the forepeak. Stringer plates are to be fitted on the tiers of beams which are to be connected by continuous welding to the shell plating and by a bracket to each frame. The scantlings of the stringer plates are to be determined from the following formulae:
width b = 75 [mm]
thickness t = 6,0 + [mm].
5.2.2 The cross sectional area of each beam is to be determined according to Section 10, C.2 for a load
P = A @ p [kN]
A = load area of a beam [m2] p = ps or pe, whichever is applicable.
5.2.3 In the after peak, tiers of beams with stringer plates generally spaced 2,6 m apart, measured vertically, are to be arranged as required under 5.2.1, as far as practicable with regard to the ship's shape.
5.2.4 Intermittent welding at the stringers in the afterpeak is to be avoided. Any scalloping at the shell plating is to be restricted to holes required for welding and for limbers.
5.2.5 Where peaks are used as tanks, stringer plates are to be flanged or face bars are to be fitted at their inner edges. Stringers are to be effectively fitted to the collision bulkhead so that the forces can be properly transmitted.
5.2.6 Where perforated decks are fitted instead of tiers of beams, their scantlings are to be determined as for wash bulkheads according to Section 12, G. The requirements regarding cross sectional area stipulated in 5.2.2 are, however, to be complied with.
5.3 Web frames and stringers
5.3.1 Where web frames and supporting stringers are fitted instead of tiers of beams, their scantlings are to be determined
as follows:
.1 Section modulus:
W = 0,55 @ e @ R2 @ ps @ nc @ k [cm3] .2 Web sectional area at the supports:
Aw = 0,05 @ e @ R1 @ ps @ k [cm2]
R = unsupported span [m], without consideration of cross ties, if any R1 = similar to R, however, considering cross ties, if any
nc = coefficient according to the following Table 9.1.
5.3.2 Vertical transverses are to be interconnected by cross ties the cross sectional area of which is to be determined according to 5.2.2.
5.3.3 Where web frames and stringers in the fore body are dimensioned by strength calculations the stresses shall not exceed the permissible stresses in 2.1.4.
Note
Where a large and long bulbous bow is arranged a dynamic pressure psdyn is to be applied unilaterally. The unilateral pressure can be calculated approximately as follows :
psdyn = po@ cF@ [kN/m2] po , cF , z and f according to Section 4, with f = 0,75.
For the effective area of psdyn, the projected area of the z-x-plane from forward to the collision bulkhead may be assumed.
Table 9.1 - Reduction coefficient nc
5.4 Web frames and stringers in 'tween decks and superstructure decks
Where the speed of the ship exceeds v0 = 1,6 [kn] or in ships with a considerable bow flare respectively, stringers and transverses according to 5.3 are to be fitted within 0,1 L from forward perpendicular in 'tween deck spaces and superstructures.
The spacing of the stringers and transverses shall be less than 2,8 m. A considerable bow flare exists, if the flare angel exceeds 40°, measured in the ship's transverse direction and related to the vertical plane.
5.5 Tripping brackets
5.5.1 Between the point of greatest breadth of the ship at maximum draft and the collision bulkhead tripping brackets spaced not more than 2,6 m, measured vertically, according to Fig. 9.3 are to be fitted. The thickness of the brackets is to be determined according to 5.2.1. Where proof of safety against tripping is provided tripping brackets may partly or completely be dispensed with.
5.5.2 In the same range. in 'tween deck spaces and superstructures of 3 m and more in height, tripping brackets according to 5.5.1 are to be fitted.
Fig. 9.3 - Tripping brackets
5.5.3 Where peaks or other spaces forward of the collision bulkhead are intended to be used as tanks. tripping brackets according to 5.5.1 are to be fitted between tiers of beams or stringers.
5.5.4 For ice strengthening, see Section 15.
6. Web frames in machinery spaces
6.1 Arrangement
6.1.1 In the engine and boiler room, web frames are to be fitted. Generally, they should extend up to the uppermost continuous deck. They are to be spaced not more than 5 times the frame spacing in the engine room.
6.1.2 For combustion engines, web frames shall generally be fitted at the forward and aft ends of the engine. The web frames are to be evenly distributed along the length of the engine.
6.1.3 Where combustion engines are fitted aft, stringers spaced 2,6 m apart are to be fitted in the engine room, in alignment with the stringers in the after peak, if any. Otherwise the main frames are to be adequately strengthened. The scantlings of the stringers shall be similar to those of the web frames. At least one stringer is required where the depth up to the lowest deck is less than 4 m.
6.1.4 For the bottom structure in machinery spaces, see Section 8, C.
6.2 Scantlings
6.2.1 The section modulus of web frames is not to be less than:
W = 0,8 @ e @ R2 @ ps @ k [cm3] The moment of inertia of web frames is not to be less than:
I = H (4,5 H n 3,5) ci @ 102 [cm4] for 3m
#
H#
10mI = H (7,25 H n 31) ci @ 102 [cm4] for H > 10 m ci = 1 + (Hu - 4) 0,07
The scantlings of the webs are to be calculated as follows :
depth h = 50 @ H [mm],
hmin = 250 mm
thickness t = [mm],
tmin = 8,0 mm.
6.2.2 Ships with a depth of less than 3 m are to have web frames with web scantlings not less than 250 x 8 mm and a minimum face sectional area of 12 cm2.
6.2.3 In very wide engine rooms it is recommended to provide side longitudinal bulkheads.