Midship

Department of Ship technology, CUSAT, B.Tech (NA&SB, Batch - XXVII

182

CHAPTER 8

MIDSHIP SECTION DESIGN


183

MIDSHIP SECTION

8.1 INTRODUCTION

Midship section design is in accordance with Ice class Rules given by Finnish Maritime Administration, Sept 2003 and the rules for classification of ships given by Lloyd’s Registrar of Shipping July 2001. Fig. 8.1 is a typical midship section of a double skin ice class tanker.

Figure 8.1 - Typical midship section of a double skin Ice class Tanker

8.1.1. Definitions

(1) L : Rule length, in m, is the distance, in meters, on the summer load water line from the forward side of the stem to the after side of the rudderpost or to the center of the rudder stock, if there is no rudder post. L is neither to be less than 96% nor to be greater than 97% of the extreme length on the summer load water line.

97% of extreme length of LWL = 264.39 m

(2) B : Breadth at amidships or greatest breadth, in meters.

B = 48.7 m

(3) D : Depth is measured, in meters, at the middle of the length L, from top of the keel to top of the deck beam at side on the uppermost continuous deck.

D = 23.76 m

(4) T : T is the Maximum Ice Class draught of the ship, in m = 16.75 m

(5) LPP : Distance in m on the summer LWL from foreside of the stem to after side of rudder post, or to the centre of the Podded unit, if there is no rudder post.

LPP = 263.00 m (6) LPAR = Length of parallel midship body, in m (approx. 92.05 m)

(7) CB : Moulded block coefficient at draught T corresponding to summer waterline, based on rule length L and moulded breadth B, as follows:


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CB = 0.84 (8) hG = Ice thickness, in m, defined in the table given by FSICR (9) h = 1 (10) Awf = Area of the waterline of the bow in m2. (11) α = Angle of the waterline at B/4 = 70 (12) φ1 = Rake of the Ice breaking stern at the centreline = 24.2 (13) φ2 = Rake of the Ice breaking stern at B/4 = 24.5 (14) DP = Diameter of propeller = 7260 mm (15) HM = Thickness of the brash ice in mid channel, in m = 1.0 m (16) HB = Thickness of the brash ice layer displaced by the stern (17) ReH = Minimum yield stress, in N/mm2, of the material defined (18) LWL = Load Waterline, at fully loaded condition. (19) BWL = Ballast Waterline at Ballast condition.

(20) b : The width of plating supported by the primary member or secondary member in m or mm respectively.

(21) be : The effective width, in m, of end brackets.

(22) bI : The minimum distance from side shell to the inner hull or outer longitudinal bulkhead measured inboard at right angles to the centre line at summer load water line, in m.

(23) le : Effective length, in m, of the primary or secondary member, measured between effective span points.

(24) ds : The distance, in m, between the cargo tank boundary and the moulded line of the side shell plating.

(25) db : The distance, in m, between the bottom of the cargo tanks and the moulded line of the bottom shell plating measured at right angles to the bottom shell plating.

(26) k : Higher tensile steel factors. For HT steels (Lloyd’s AH32, DH32 & EH32), k = 0.78

(27) s : Spacing in m of ordinary stiffeners or primary support as applicable.

(28) S : Overall span of frame, in mm

(29) t : Thickness of plating, in mm.

(30) Z : Section modulus, in cm3, of the primary or secondary member, in association with an effective width of attached plating.

(31) RB : Bilge radius, in mm.

(32) FD,FB : Local scantling reduction factor above neutral axis and below neutral axis respectively. FD = 0.67, for plating and 0.75, for longitudinals

FB = 0.67, for plating and 0.75, for longitudinals

(33) dDB : Rule depth of center girder, in mm

Moulded displacement (m3) at draught T


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(34) SS : Span of the vertical web, in m

(35) tW : Thickness of web, in mm

(36) tB : Thickness of end bracket plating, in mm

8.1.2 Class Notation

Vessel is designed to be classed as ‘+100 A1(ice) Double Hull Oil Tanker ESP.’ ESP means Enhanced Survey Program. This is for Ice navigating tanker having integral cargo tanks for carriage of oil having flash point > 60o C. Where the length of the ship is greater than 190m, the scantlings of the primary supporting structure are to be assessed by direct calculation and the Ship Right notations Structural Design Assessment (SDA), Fatigue Design Assessment (FDA) and Construction Monitory (CM) are mandatory.

8.1.3 Cargo Tank Boundary Requirements Minimum double side width (ds)

ds = 0.5 + (dwt/20,000) or ds = 2.0 m Whichever is lesser But ds should not be less than 1 m. ds = 0.5 + (150000/20,000) = 8.0 m Double side width is taken as 2.8 m to get the required ballast volume. ∴ ds = 3.0 m

Minimum double bottom depth (dB)

dB = B/15 or dB = 2.0 m

Whichever is lesser

dB = 48.76/15 = 3.25 m

A double bottom height of 3.0 m is provided to get the required ballast volume.

∴ dB = 3.0 m

Structural configuration adopted has a single centreline longitudinal bulkhead. For length of cargo tanks and tank boundaries refer General Arrangement Plan.

8.1.4 Type Of Framing System [LRS Part 4, Chapter 9, Section 1.3.10, 1.3.11]

The bottom shell, inner bottom and deck are longitudinally framed (for L > 75m). The side shell, inner hull bulkheads and long bulkheads are also longitudinally framed (L > 150m). When the side shell in long framed, the inner hull bulkhead is also to be framed longitudinally. Primary members are defined as girders, floors, transverses and other supporting members.


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8.2 LONGITUDINAL STRENGTH

8.2.1 Minimum Hull Section Modulus [LRS Part 3, Chapter 4, Section 5]

The hull midship section modulus about the transverse neutral axis, at the deck or keel is to be not less than

Z min = f1KL C1L2B (CB + 0.7) x 10-6 m3

f1 = ship’s service factor, specially considered depending upon the service restriction and in any event should not be less than

0.5 For unrestricted sea going service f1 = 1.0

∴f1 taken as 1 and KL = 0.78 (Grade DH32/EH32)

C1 = 10.75 – [(300-L)/100] 1.5 for 90<L<300m

= 10.537

CB = Block Coefficient = 0.84

∴ Zmin = 43.09 m3

8.2.2 Hull Envelope Plating

1. Deck plating 2. Sheer strake and shell plating above Ice

strengthened region. 3. Ice strengthened shell 4. Side shell below ice strengthening 5. Bilge 6. Bottom shell 7. Keel

Fig. 8.2 Itemization of parts


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For longitudinally framed system the web structure:

Fig 8.3 Framing system

8.2.3 Minimum require Power

( ) [ ]kW

D1000/R

KPP

2/3CH

e= ;

Table 8.1 Values of Ka

Propeller type or machinery

CP or electric or hydraulic propulsion machinery

FP propeller

1 propeller 2.03 2.26 2 propellers 1.44 1.60 3 propellers 1.18 1.31

Ke = 1.60 RCH is the resistance in Newton of the ship in a channel with brash ice and a consolidated layer:

( ) ( )L

ABLTCHLCHCBHHCCCR wf

3

252FPAR4Fψ

2MF321CH ⎟

⎠⎞

⎜⎝⎛++++++= μC

Cμ = 0.15cosϕ2 + sinψsinα = 0..546 Cμ is to be taken equal or larger than 0.45 °≤=−⋅= 45if0Cand,115.2047.0C ψψ ψψ

⎟⎠⎞

⎜⎝⎛=

αϕψ

sintanarctan 2 = 30.17o


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ψC = 25.89 HF = 0.26 + (HMB)0.5

= 7.2 m HM = 1.0 for ice classes IA and IA Super = 0.8 for ice class IB = 0.6 for ice class IC HM = 1.0 C1 and C2 take into account a consolidated upper layer of the brash ice and are to be taken as zero for ice classes IA, IB and IC. For a ship with a bulbous bow, ϕ1 shall be taken as 90°. Given: C3 = 845 kg/(m2s2) C4 = 42 kg/(m2s2) C5 = 825 kg/s2

5 ≤ 3

2BLT

⎟⎠⎞

⎜⎝⎛ ≤ 20

P = 21.2 MW (approx) 8.2.4 Ice load Height of load area An ice-strengthened ship is assumed to operate in open sea conditions corresponding to a level ice thickness not exceeding ho. The design height (h) of the area actually under ice pressure at any particular point of time is, however, assumed to be only a fraction of the ice thickness. The values for ho and h are given in the following table. Table 8.2 Values of ho and h

8.2.5 Ice pressure The design ice pressure is determined by the formula:

p = cd · c1 · ca · po [MPa], where

Ice Class ho [m] h [m] IA Super

IA IB IC

1.0 0.8 0.6 0.4

0.35 0.30 0.25 0.22


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cd = a factor which takes account of the influence of the size and engine output of the ship. It is calculated by the formula:

a and b are given in the following table: Table 8.3 Values of a and b

Δ = the displacement of the ship at maximum ice class draught [t] = 183376.12 t P = the actual continuous engine output of the ship [kW] 38250 KW K = 83.75 a = 2 b = 286 c1 = a factor which takes account of the probability that the design ice pressure occurs in a certain region of the hull for the ice class in question. The value of c1 is given in the following table: Table 8.4 values of c1

1000b k acd

+⋅=

1000P k ⋅Δ

=

R e g i o n Forward Midship & Aft

a b

k ≤ 12 k > 12 k ≤ 12 k > 12 30 230

6 518

8 214

2 286


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Table 8.4 values of c1

c1 = 1 ca = a factor which takes account of the probability that the full length of the area under consideration will be under pressure at the same time. It is calculated by the formula:

0.6 minimum; 1.0 maximum;44

5-47=c aa

l

la shall be taken as follows: Table 8.5 Values of la

po = the nominal ice pressure; the value 5.6 Mpa shall be used. 8.3 Calculations for Ice strengthened part 8.3.1 Vertical extension of Ice Belt The vertical extension of the ice belt shall be as follows: Ice Belt is from 7.00 m to 17.35 ma long d ship’s depth from keel. Table 8.6 Extension of Ice strengthening at midship

Structure Type of framing la [m] la [m] Ca [m] P Shell Transverse Frame spacing 0.35 1.028 2.612

Longitudinal 2 ⋅ frame spacing 0.7 0.989 2.511 Frames Transverse Frame spacing 0.35 1.028 2.612

Longitudinal Span of frame 4.25 0.585 1.486Ice stringer Span of stringer 4.25 0.585 1.486Web frame 2 ⋅ web frame spacing 8.5 0.102 0.260

Ice Class Above LWL [m]

Below BWL [m]

IA Super 0.6 0.75 IA 0.5 0.6 IB 0.4 0.5 IC 0.4 0.5

Ice Class R e g i o n Forward Midship Aft

IA Super IA IB IC

1.0 1.0 1.0 1.0

1.0 0.85 0.70 0.50

0.75 0.65 0.45 0.25


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8.3.2 Plate thickness in the ice belt For transverse framing the thickness of the shell plating shall be determined by the

formula: For longitudinal framing the thickness of the shell plating shall be determined by the formula:

S = the frame spacing [m]

pPL = 0.75 p [MPa]

p = 1.88

1.0maximum;1.8)(h/s

4.23.1f 21 +−=

= 0.764

1h/swhen;(h/s)0.40.6f2 ≤+=

f2 = 1.4 - 0.4 (h/s); when 1≤ h/s < 1.8

= 1.0

h = 0.35

σy = yield stress of the material [N/mm2]

σy = 235 N/mm2 for normal-strength hull structural steel

σy = 315 N/mm2 or higher for high-strength hull structural steel If steels with different yield stress are used, the actual values may be substituted for the above ones if accepted by the classification society. tc = increment for abrasion and corrosion [mm]; normally tc shall be 2 mm

t = 20.05 mm

Taken t = 24 mm

[ ]mmtpf s 667 t cy

PL1 +⋅

=σ

[ ]mmtf

p s 667 t c

2

PL +⋅

=yσ


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Table 8.7 Vertical extension of ice strengthening

The vertical extension of the ice strengthening of the framing shall be at least as Vertical extension of ice strengthening in framing is from 5.41 m to 18.55 m. 8.3.3 Transverse frames Section modulus The section modulus of a main or intermediate transverse frame shall be calculated by

the formula: p = ice pressure

s = frame spacing [m]

h = height of load area

l = span of the frame [m]

mt = l5h/-7

m7 o

σy = yield stress [N/mm2]

Ice Class Region Above LWL [m]

Below BWL [m]

IA Super

From stem to 0.3L abaft it

1.2

To double bottom or below top of floors

Abaft 0.3L from

stem

1.2

1.6

midship 1.2 1.6 aft 1.2 1.2

IA, IB, IC

From stem to 0.3L abaft it

1.0

1.6

Abaft 0.3L from stem

1.0

1.3

Midship 1.0 1.3 Aft 1.0 1.0

[ ]36

t

cm10m

h s p Zy

lσ⋅⋅⋅⋅

=


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mo = values are given in the following table: Table 8.8 Values of mo

Z = 580.4 cm3 8.3.4 Longitudinal frames The section modulus of a longitudinal frame shall be calculated by the formula:

The shear area of a longitudinal frame shall be:

This formula is valid only if the longitudinal frame is attached to supporting structure by brackets

[ ]24

y

3 cm102

hpf3 A

σl⋅⋅⋅⋅

=

[ ]36

y

243 cm10m

hpff Z

σ⋅⋅⋅⋅⋅

=l


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f3 = factor which takes account of the load distribution to adjacent frames

f3 = (1 - 0.2 h/s) = 0.8.

f4 = factor which takes account of the concentration of load to the point of support,

f4 = 0.6

p = ice pressure

h = height of load area

s = frame spacing [m]

l = span of frame [m]

m = boundary condition factor; m = 13.3 for a continuous beam; where the boundary conditions deviate significantly from those of a continuous beam, e.g. in an end field, a smaller boundary factor may be required.

σy = yield stress Z = 1076.5 cm3 A = 48.62 cm2 Scantling selected 330x15 HB A = 65.9 cm2 8.3.5 Stringers within the ice belt The section modulus of a stringer situated within the ice belt (see 4.3.1) shall be calculated by the formula:

[ ]36

y

25 cm 10m

hpf Zσ⋅⋅⋅⋅

=l

The shear area shall be:

[ ]24

y

5 cm102

hpf3 Aσ

l⋅⋅⋅⋅=

The product p ⋅ h shall not be taken as less than 0.30.

f5 = factor which takes account of the distribution of load to the transverse frames;

to be taken as 0.9

σy = yield stress

Z = 2153 cm3

A = 53.34 cm2


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8.3.6 Load on Web frames in Ice Belt The load transferred to a web frame from an ice stringer or from longitudinal framing shall be calculated by the formula: F = p ⋅ h ⋅ S [MN] The product p ⋅ h shall not be taken as less than 0.30

S = distance between web frames [m] F = 0.76 MN

8.4 Dimensions of non Ice strengthened parts:

8.4.1 Deck plating: [Design Ice class and steel grade, RS]

t = 20 mm

For Lloyd’s grade DH32, and for Russian Ice class LU4 or FMA Ice class 1A.

8.4.2 Sheer strake: [Design Ice class and steel grade, RS]

t = 20 mm

For Lloyd’s grade EH32, and for Russian Ice class LU4 or FMA Ice class 1A.

8.4.3 Side shell below Ice strengthening:

The greatest of the following is to be taken: t = 0.001s (0.059L1 + 7) √ FB/kL

= 11.81 mm But not less than

t = 0.0042 s√ hT1k s = spacing of shell longitudinals = 700 mm

hT1 = T + Cw m but need not be taken greater than 1.36T hT1 = 23.12 Cw = a wave head, in meters, 7.71 x 10–2Le–0,0044L Cw = 6.37 ∴ t = 12.48 mm

Selected t = 20 mm (Lloyd’s Grade DH32)


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8.4.4 Bottom shell and bilge

√ t = 0.0052s

hT2 = T + 0.5CW m but need not be taken greater than 1.2T = 19.93 FB = 0.67 (refer ‘DEFINITIONS’) k = 0.78 (refer ‘DEFINITIONS’) ∴ t = 10.27 mm Selected t = 18 mm (Lloyd’s Grade DH32)

8.4.5 Keel Plating

Keel plating should not be less than thickness of bottom shell + 2 mm

∴t = 20 mm,

But need not exceed t = 25 √ k = 22.08 mm

Selected t = 22 mm

Width of keel plate is to be not less than 70B mm, but need not exceed 1800 mm and is to be not less than 750 mm. (LRS part 4, chapter1, and table 1.5.1)

70B = 3409 mm

Selected w = 1800 mm

8.4.6 Inner bottom Plating t = t0 / √ 2-FB

t0 = 0.005s√ kh1

s = spacing of inner bottom longitudinal = 700mm

k = 0.78 h = distance in m, from the plate in consideration to the highest point of the tank, excluding hatchway.

R = 0.354

b1 = B/2 = 24.35 m

h1 = 0.72 (h+Rb1)

= 21.15

hT2k

1.8-FB


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t0 = 14.22 mm

t = 12.33 mm Selected = 14 mm (Lloyd’s Grade DH32)

8.5 Hull Framing [LRS Part 4, Chapter 9, Section 5]

8.5.1 Bottom Longitudinals

The section modulus of bottom longitudinals within the cargo tank region is not to be less than greater of the following:

a) Z = 0.056kh1sle2F1FS cm3

K = 0.78 (refer ‘DEFINITIONS’)

h1 = (h0 + D1/8), but in no case be taken less than L1/56 m or (0.00L1 + 0.7) m, whichever is greater & need not be taken greater than (0.75 D + D1/8), for bottom longitudinals.

= 19.82m

h0 = distance in m, from the midpoint of span of stiffener to highest point of tank, excluding hatchway.

= 22 m D1 = 16 m (refer ‘DEFINITIONS’)

s = spacing of bottom longitudinals = 700 mm

le = effective span of longitudinals which are assumed to be supported by web frames spaced at 5s, where s is the basic frame spacing in midship region (850 mm ) not to be taken less than 1.5 m in double bottom and 2.5 m else where.

le = 4.25 m

F1 = Dc1/(25D-20h)

= 0.133

c1 = 75/(225 – 150FB), at base line of ship.

FB = 0.75 (refer ‘DEFINITIONS’)

∴c1 = 0.667

h = distance of longitudinal below deck at side, in meters

= 23.76 m

D = 23.76 m (refer ‘DEFINITIONS’)

∴F1 = 0.133

FS = 1, at upper deck at side and at the base line.


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∴Z = 1459.5 cm3

b) Z = 0.0051kh3sle2F2 cm3

k = 0.78 (refer ‘DEFINITIONS’)

h3 = 75D+Rb1

b1 = 24.35 m

R = (0.45+0.1 L/B)(0.54 – L/1270) = 0. 354

D1 = 16 m

h3 = 26.44 m

F2 = Dc2/ (3.18D-2.18h) = 0.785

c2 = 165/ (345-180FB)

s = 700 mm

le = 4.25 m

∴Z = 1044.8 cm3

Greater of the two is to be taken, i.e. Z = 1459.5 cm3

Selected 400 x 18 HB

8.5.2 Deck Longitudinals (LRS, Part 4, Chapter 9.5.3.1)

The modulus of bottom longitudinals within the cargo tank region is not to be less than greater of the following: a) Z = 0.056kh1sl2eF1FS cm3

k = 0.78 (refer ‘DEFINITIONS’) h1 = (h0 + D1/8), but in no case be taken less than L1/56 m. h0 = 0 ( for deck longitudinals) D1 = 16 (h0 + D1/8) = 2 L1 = 190 L1/56 = 3.39 0.01L1 +0.7 = 2.6 ∴h1 = L1/56 = 3.39 s = 700 mm le = 4.25m F1 = Dc1 / (4D + 20h) h = 0 (for deck longitudinals) c1 = 60 / (225 – 165FD) at deck FD = 0.75 (refer ‘DEFINITIONS’) ∴ c1 = 0.595


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∴F1 = 0.148 Fs = 1, at upper deck at side and at baseline of ship ∴Z = 277.06 cm3

b) Z = 0.0051kh3sle2F2 cm3

R = 0.354 bi = B/2 = 24.35 m h3 = h0 + Rb1 = 8.62 m s = 700 mm le = 4.25m F2 = Dc2 / (D + 2.18h) c2 = 165 / (345 – 180FD) FD = 0.75 (refer ‘DEFINITIONS’) ∴c2 = 1.0 ∴F2 = 1.0 ∴Z = 433.5 cm3

Greatest of the two is to be taken, i.e. Z = 433.5 cm3

250 x 12 HB section is selected

8.5.3 Side Shell Longitudinals (LRS Part 4, Chapter 9. 5.3.1)

From standardization point of view the side shell is divided into longitudinal fields as shown in fig 8.3. Design of the longitudinals for each field is done using the information for the lowest longitudinal in each field. 8.5.4 Inner hull and CL bulkhead longitudinals

The modulus of side shell longitudinals within the cargo tank region is not to be less than greater of the following:

a) Z = 0.056kh1sle2F1Fs cm3

b) Z = 0.0051kh3sle2F2 cm3

Where,

h1 = (h0 + D1/8), but in no case be taken less than L1/56 m or 0.01L1 +0.7 m whichever is the greater.

s = 700 mm

le = 4.25m

k = 0.78

FD = 0.75

D1 = 16

L1 = 190m


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L1/56 = 3.39

h = distance of longitudinal below deck at side, in meters

h3 = h0 + Rb1

For side longitudinals above D/2,

F1 = Dc1 / (4D + 20h)

F2 = Dc2 / (D + 2.18h)

For side longitudinals below D/2,

F1 = Dc1/(25D-20h)

F2 = Dc2/(3.18D-2.18h)

c1 = 60 / (225 – 165FD) at deck

= 1.0 at D/2

= 75/(225 – 150FB), at base line of ship

c2 = 165/(345 – 180FB) at deck

= 1.0 at D/2

= 165/(345 – 180FD) at baseline of ship

Fig 8.4 Side shell regions


201

Table 8.8 – Determination of scantlings of side shell longitudinals

ITEM REG 1 REG 2 ho 5.21 20.76 D1 16 16

h1= h0+D1/8 7.21 22.76 h3 13.83 29.38 F1 0.113 0.0777 F2 0.702 0.5468 Fs 1 1

a) Z 450.405 976.925 b) Z 488.61 808.12

Taken Z (cm3) 488.61 976.92 Section HB HB

Scantling 260 x 11 340 x 13 Z of taken

3488.61 976.92

8.6 Inner Hull, Inner Bottom and Longitudinal Bulkheads

(LRS Part 4, Chapter 9, Section 6)

The inner hull, inner bottom and longitudinal bulkheads are longitudinally framed. The symbols used in this section are defined as follows:

b1 = the greatest distance in meters, from the centre of the plate panel or midpoint of the stiffener span, to the corners at top of the tank on either side.

c1 = 60 / (225 – 165FD) at deck

= 1.0 at D/2

= 75/(225 – 150FB), at base line of ship

c2 = 165/(345 – 180FB) at deck

= 1.0 at D/2

= 165/(345 – 180FD) at baseline of ship

h = load height, in meters measured vertically as follows:


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(a) for bulkhead plating the distance from a point one third of the height of the plate panel above its lower edge to the highest point of the tank, excluding hatchway

(b) for bulkhead stiffeners or corrugations, the distance from the midpoint of span of the stiffener or corrugation to the highest point of the tank, excluding hatchway

h1 = (h + D1/8), but not less than 0.72 (h + Rb1) h2 = (h + D1/8), in meters, but in no case be taken less than L1/56 m or (0.01L1 + 0.7) m, whichever is greater h3 = distance of longitudinal below deck at side, in meters, but is not to

be less than 0 h4 = h + Rb1

h5 = h2 but is not to be less than 0.55h4 t0 = 0.005s √kh1

t1 = t0(0.84 + 0.16(tm/t0)2) tm = minimum value of t0 within 0.4D each side of mid depth of bulkhead

8.6.1 Inner Hull Longitudinal Bulkhead Plating

For the determination of scantlings of longitudinal bulkhead plating and inner hull plating’s areas follows. (Refer fig 8.4)

ITEM Region 1 Region 2 ice belt

h 5.41 19.09 15.35 D1 16 16 16

h1 10.101 21.09 17.35 h2 7.41 21.09 17.35 h4 14.029 27.7099 23.96 h5 7.7164 21.09 17.35 t0 9.824 14.195 12.875 t1 10.952 13.7928 12.875

taken 12 14 13

8.6.2 CL Longitudinal Bulk Head Longitudinals and Inner Hull Longitudinals

Inner hull and longitudinal bulkheads are to be longitudinally framed . The modulus of longitudinals is not to be less than greater of the following: (a) Z = 0.056kh2sl2eF1 cm3 (b) Z = 0.0051kh4sl2eF2 cm3


203

The inner hull and bulkhead plating is divided into various strakes for the determination of center line bulkhead longitudinals and inner hull longitudinals.

s = 700 mm

le = 4.25m

Table.8.9 Determination of scantlings of CL longitudinal bulkhead longitudinal and inner hull longitudinal.

ITEM Region 1 Region 2 Between 1 & 2

b1 5.41 19.09 15.35 h1 24.35 24.35 24.35 h2 16 16 16 h3 10.10 21.09 17.35 h4 7.41 21.09 17.35 c1 6.5 17 13.5 c2 14.03 27.71 23.97 F1 0.7 0.7 1 F2 0.87 0.87 1 Z1 456.380 912.923 751.030 Z2 405.448 435.494 692.703

Taken Z (cm3) 456.380 912.923 751.030

Section HB HP HP Scantling 250 X 13 325 X 17 325 X 12

8.6.3 Inner Bottom Plating and Longitudinals

The inner bottom is to be longitudinally framed and the inner bottom plating thickness is to be

t = t0 / √ 2-FB

t0 = 0.005s√ kh1

s = spacing of inner bottom longitudinal = 700mm

k = 0.78 h = distance in m, from the plate in consideration to the highest

point of the tank, excluding hatchway = 20.76 m R = 0.354 (refer previous sections) b1 = B/2 = 24.35 m h1 = 0.72 (h+Rb1) = 21.15 t0 = 14.21 mm


204

t = 12.32 mm Selected = 14 mm

The modulus of longitudinals is not to be less than greater of the following: (a) Z = 0.056kh2sl2eF1 cm3

h = 19.38 m D1 = 16 m h2 = h + D1 / 8 = 22.76 m F1 = 0.078 ∴Z = 985.2 cm3

(b) Z = 0.0051kh4sl2eF2 cm3 h4 = h + Rb1 = 27.709m F2 = 0.316

∴Z = 440.67 cm3

Selected Z = 985.2 cm3.

Selected HB 330 x 13

8.7 Primary Members Supporting the Hull Longitudinal Framing 8.7.1 Centre girder (LRS Part 4, Section 9.3.3) (a) Minimum depth of centre girder

dDB = 28B + 205√ T mm dDB = 2202.6 mm dDB = 3000 mm Given 3.0 m.

(b) Minimum thickness of centre girder (LRS, Part 4.9.3.4) t = (0.008 dDB + 1) √ k = 22.07 mm Given thickness = 22 mm

8.7.2 Floors and Side Girders

t = (0.007dDB + 1) √ k

= 19.43 mm

But not to exceed 12√ k = 10.6 mm

Given thickness = 10.6 mm

∴t = 16 mm

8.7.3 Deck Transverses (LRS Part 4.10.2.8)

Section modulus of deck transverses is not to be less than


205

Z = 53.75 (0.0269sL + 0.8) (ST + 1.83) k cm3

s = 4.25 m L = 229.8 m ST = span of transverse = 8.116 m ∴Z = 12871.3 cm3

Taken T section 1500 X 14 +600 X 20 is selected.

8.7.4 Vertical web on centreline longitudinal bulkhead Section modulus of vertical web is to be not less than

Z = K3shsSs2k (sm3)

K3 = 1.88, s = 4.25 hs = distance between the lower span point of the vertical web

and the moulded deckline at centreline, in meters = 20 m Ss = span of vertical web, in meters, and is to be measured between end span points. = 12.75 m ∴ Z = 18476.0 cm3

Taken T section 1250x 12+ 500x 18

8.8 Primary Members End Connections [LRS Part 3, Chapter 10, Section 3]

The following relations govern the scantlings of bracket:

(a + b) ≥ 2l

a ≥ 0.8 l

b ≥ 0.8 l l = 90 2 - 1 mm

8.8.1 Bracket connecting deck transverse and inner hull

l = 90 2 - 1 mm Z = 12871.3 cm3

Z

(14 + √ Z) √

Z

(14 + √ Z) √


206

l = 90 {2 (√12871.3 / [14 + √ 12871.3]) – 1} = 1718.8 mm a ≥ 0.8l = 1375 mm

b ≥ 0.8l = 1375 mm Given a = 2300 mm and b = 2000 mm t = thickness of web itself = 25 mm Flange breadth to be not less than bf = 40 (1 + Z / 1000) mm, but not less than 50mm = 40 (1 + 12871.3 / 1000) = 554 mm Taken 750 mm

8.8.2 Bracket connecting deck transverse and center line bulkhead web l = 90{ 2 - 1} mm Z = 14602 cm3 l = 90 {2 (√14602/ [14 + √ 14602]) – 1} = 1783.1 mm a ≥ 0.8l = 1426.5 mm b ≥ 0.8l = 1426.5 mm Given a = 2400 mm and b = 2000 mm t = thickness of web itself = 25 mm Flange breadth to be not less than bf = 40 (1 + Z / 1000) mm, but not less than 50mm = 40 (1 + 14602/ 1000) = 624.08 mm Taken 750 mm

8.8.3 Bracket connecting centre line vertical web and inner bottom plating

l = 90{ 2 - 1} mm

Z = 14602cm3 l = 90 {2 (√14602/ [14 + √ 14602]) – 1} = 1783.1 mm a ≥ 0.8l = 1426.5 mm

Z

(14 + √ Z) √

Z

(14 + √ Z) √


207

b ≥ 0.8l = 1426.5 mm Given a = 2400 mm and b = 2000 mm t = thickness of web itself = 25 mm Flange breadth to be not less than bf = 40 (1 + Z / 1000) mm, but not less than 50mm = 40 (1 + 14602/ 1000) = 624.08 mm Taken 750 m

Table 8.3 Section Modulus Calculation

ITEMS L

(m) t(m) NO AREA (m2) LEVER A*L

A*L2 )m4( Iown)m4(

Deck Plate 23.5 0.02 2 0.94 23.76 22.334 530.6653 1.57E-05

Sheerstrake Plate 3 0.02 2 0.12 22.26 2.6712 59.46091 0.045

Above IceBelt Plate 2.5 0.02 2 0.1 19.51 1.951 38.06401 0.026042

Ice Belt Plate 12.5 0.024 2 0.6 12 7.2 86.4 3.90625

Below Ice Belt Plate 3 0.02 2 0.12 4.26 0.5112 2.177712 0.045

Bottom Shell Plate 19 0.02 2 0.76 0.01 0.0076 0.000076 1.27E-05

Bottom Bilge Plate 6 0.02 2 0.24 1.25 0.3 0.375 0.36

Keel Plate 1.8 0.022 1 0.0396 0.011 0.0004 4.79E-06 1.6E-06

Margin Plate 4 0.014 2 0.112 4.5 0.504 2.268 0.074667

Inn Bot Plate 18.35 0.014 2 0.5138 3 1.5414 4.6242 4.2E-06

Centre Girder 3 0.022 1 0.066 1.5 0.099 0.1485 0.0495

Side Girder 3 0.015 6 0.27 1.5 0.405 0.6075 0.03375

CL bhd reg 1 5 0.012 3 0.18 21.26 3.8268 81.35777 0.125 CL bhd reg Bb/w 1 &2 13 0.013 1 0.169 12.26 2.0719 25.40198 2.380083

CL bhd reg 2 2.76 0.014 1 0.03864 4.38 0.1692 0.741285 0.024529

IB hull plate reg 1 5 0.012 2 0.12 21.26 2.5512 54.23851 0.125 IB hull plate reg b/w 1&2 13 0.013 2 0.338 12.26 4.1439 50.80397 2.380083

IB hull plate reg 2 2.76 0.014 2 0.07728 4.38 0.3385 1.48257 0.024529

Wing Tank Girder 1 3 0.012 2 0.072 6 0.432 2.592 4.32E-07






Deck Longitudinals 250 x 12 68 0.26316 23.6 6.2106 146.5696


208

Inner Hull Longls 1 250 x 13 2 0.0084 23.06 0.1937 4.466814

2 250 x 13 2 0.0084 22.36 0.1878 4.199745

3 250 x 13 2 0.0084 21.66 0.1819 3.940907

4 250 x 13 2 0.0084 20.96 0.1761 3.690301

5 250 x 13 2 0.0084 20.26 0.1702 3.447928

6 250 x 13 2 0.0084 19.56 0.1643 3.213786

7 250 x 13 2 0.0084 18.86 0.1584 2.987877

8 325 x 12 2 0.0108 18.51 0.1999 3.700297

9 325 x 12 2 0.0108 18.16 0.1961 3.561684

10 325 x 12 2 0.0108 17.81 0.1923 3.425718

11 325 x 12 2 0.0108 17.46 0.1886 3.292397

12 325 x 12 2 0.0108 17.11 0.1848 3.161723

13 325 x 12 2 0.0108 16.76 0.181 3.033694

14 325 x 12 2 0.0108 16.41 0.1772 2.908311

15 325 x 12 2 0.0108 16.06 0.1734 2.785575

16 325 x 12 2 0.0108 15.71 0.1697 2.665484

17 325 x 12 2 0.0108 15.36 0.1659 2.54804

18 325 x 12 2 0.0108 15.01 0.1621 2.433241

19 325 x 12 2 0.0108 14.66 0.1583 2.321088

20 325 x 12 2 0.0108 14.31 0.1545 2.211582

21 325 x 12 2 0.0108 13.96 0.1508 2.104721

22 325 x 12 2 0.0108 13.61 0.147 2.000507

23 325 x 12 2 0.0108 13.26 0.1432 1.898938

24 325 x 12 2 0.0108 12.91 0.1394 1.800015

25 325 x 12 2 0.0108 12.56 0.1356 1.703739

26 325 x 12 2 0.0108 12.21 0.1319 1.610108

27 325 x 12 2 0.0108 11.86 0.1281 1.519124

28 325 x 12 2 0.0108 11.51 0.1243 1.430785

29 325 x 12 2 0.0108 11.16 0.1205 1.345092

30 325 x 12 2 0.0108 10.81 0.1167 1.262046

31 325 x 12 2 0.0108 10.46 0.113 1.181645

32 325 x 12 2 0.0108 10.11 0.1092 1.103891

33 325 x 12 2 0.0108 9.76 0.1054 1.028782

34 325 x 12 2 0.0108 9.41 0.1016 0.956319

35 325 x 12 2 0.0108 9.06 0.0978 0.886503


209

36 325 x 12 2 0.0108 8.71 0.0941 0.819332

37 325 x 12 2 0.0108 8.36 0.0903 0.754808

38 325 x 12 2 0.0108 8.01 0.0865 0.692929

39 325 x 12 2 0.0108 7.66 0.0827 0.633696

40 325 x 12 2 0.0108 7.31 0.0789 0.57711

41 325 x 12 2 0.0108 6.96 0.0752 0.523169

42 325 x 12 2 0.0108 6.61 0.0714 0.471875

43 325 x 12 2 0.0108 6.26 0.0676 0.423226

44 325 x 17 2 0.0134 5.76 0.0772 0.44458

45 325 x 17 2 0.0134 5.26 0.0705 0.370746

46 325 x 17 2 0.0134 4.76 0.0638 0.303612

47 325 x 17 2 0.0134 4.26 0.0571 0.243178

48 325 x 17 2 0.0134 3.76 0.0504 0.189444

Bottom Longitudinals 400 x 18 64 0.64 0.2 0.128 0.0256

Inner Bottom Longls 330 x 13 50 0.32 2.85 0.912 2.5992

Side longitudinals 1 250 x 13 2 0.0084 23.06 0.1937 4.466814

2 250 x 13 2 0.0084 22.36 0.1878 4.199745

3 250 x 13 2 0.0084 21.66 0.1819 3.940907

4 250 x 13 2 0.0084 20.96 0.1761 3.690301

5 250 x 13 2 0.0084 20.26 0.1702 3.447928

6 250 x 13 2 0.0084 19.56 0.1643 3.213786

7 250 x 13 2 0.0084 18.86 0.1584 2.987877

8 330 x 15 2 0.0132 18.51 0.2443 4.522585

9 330 x 15 2 0.0132 18.16 0.2397 4.35317

10 330 x 15 2 0.0132 17.81 0.2351 4.186989

11 330 x 15 2 0.0132 17.46 0.2305 4.024041

12 330 x 15 2 0.0132 17.11 0.2259 3.864328

13 330 x 15 2 0.0132 16.76 0.2212 3.707848

14 330 x 15 2 0.0132 16.41 0.2166 3.554603

15 330 x 15 2 0.0132 16.06 0.212 3.404592

16 330 x 15 2 0.0132 15.71 0.2074 3.257814

17 330 x 15 2 0.0132 15.36 0.2028 3.114271

18 330 x 15 2 0.0132 15.01 0.1981 2.973961

19 330 x 15 2 0.0132 14.66 0.1935 2.836886


210

20 330 x 15 2 0.0132 14.31 0.1889 2.703045

21 330 x 15 2 0.0132 13.96 0.1843 2.572437

22 330 x 15 2 0.0132 13.61 0.1797 2.445064

23 330 x 15 2 0.0132 13.26 0.175 2.320924

24 330 x 15 2 0.0132 12.91 0.1704 2.200019

25 330 x 15 2 0.0132 12.56 0.1658 2.082348

26 330 x 15 2 0.0132 12.21 0.1612 1.96791

27 330 x 15 2 0.0132 11.86 0.1566 1.856707

28 330 x 15 2 0.0132 11.51 0.1519 1.748737

29 330 x 15 2 0.0132 11.16 0.1473 1.644002

30 330 x 15 2 0.0132 10.81 0.1427 1.542501

31 330 x 15 2 0.0132 10.46 0.1381 1.444233

32 330 x 15 2 0.0132 10.11 0.1335 1.3492

33 330 x 15 2 0.0132 9.76 0.1288 1.2574

34 330 x 15 2 0.0132 9.41 0.1242 1.168835

35 330 x 15 2 0.0132 9.06 0.1196 1.083504 36 330 x 15 2 0.0132 8.71 0.115 1.001406

37 330 x 15 2 0.0132 8.36 0.1104 0.922543

38 330 x 15 2 0.0132 8.01 0.1057 0.846913

39 330 x 15 2 0.0132 7.66 0.1011 0.774518

40 330 x 15 2 0.0132 7.31 0.0965 0.705357

41 330 x 15 2 0.0132 6.96 0.0919 0.639429

42 330 x 15 2 0.0132 6.61 0.0873 0.576736

43 330 x 15 2 0.0132 6.26 0.0826 0.517276

44 340 x 13 2 0.012 5.56 0.0667 0.370963

45 340 x 13 2 0.012 4.86 0.0583 0.283435

46 340 x 13 2 0.012 4.16 0.0499 0.207667

47 340 x 13 2 0.012 3.46 0.0415 0.143659

48 340 x 13 2 0.012 2.76 0.0331 0.091411

49 340 x 13 2 0.012 2.06 0.0247 0.050923

50 340 x 13 2 0.012 1.36 0.0163 0.022195

51 340 x 13 2 0.012 0.66 0.0079 0.005227

CL Longl Bulkhead

1 250 x 13 1 0.0042 23.06 0.0969 2.233407

2 250 x 13 1 0.0042 22.36 0.0939 2.099872


211

3 250 x 13 1 0.0042 21.66 0.091 1.970454

4 250 x 13 1 0.0042 20.96 0.088 1.845151

5 250 x 13 1 0.0042 20.26 0.0851 1.723964

6 250 x 13 1 0.0042 19.56 0.0822 1.606893

7 250 x 13 1 0.0042 18.86 0.0792 1.493938

8 325 x 12 1 0.0054 18.16 0.0981 1.780842

9 325 x 12 1 0.0054 17.46 0.0943 1.646199

10 325 x 12 1 0.0054 16.76 0.0905 1.516847

11 325 x 12 1 0.0054 16.06 0.0867 1.392787

12 325 x 12 1 0.0054 15.36 0.0829 1.27402

13 325 x 12 1 0.0054 14.66 0.0792 1.160544

14 325 x 12 1 0.0054 13.96 0.0754 1.052361

15 325 x 12 1 0.0054 13.26 0.0716 0.949469

16 325 x 12 1 0.0054 12.56 0.0678 0.851869

17 325 x 12 1 0.0054 11.86 0.064 0.759562

18 325 x 12 1 0.0054 11.16 0.0603 0.672546

19 325 x 12 1 0.0054 10.46 0.0565 0.590823

20 325 x 12 1 0.0054 9.76 0.0527 0.514391

21 325 x 12 1 0.0054 9.06 0.0489 0.443251

22 325 x 12 1 0.0054 8.36 0.0451 0.377404

23 325 x 12 1 0.0054 7.66 0.0414 0.316848

24 325 x 12 1 0.0054 6.96 0.0376 0.261585

25 325 x 12 1 0.0054 6.26 0.0338 0.211613

26 325 x 17 1 0.0067 5.56 0.0373 0.207121

27 325 x 17 1 0.0067 4.86 0.0326 0.158251

28 325 x 17 1 0.0067 4.16 0.0279 0.115948

29 325 x 17 1 0.0067 3.46 0.0232 0.08021

Total 30 7.75748 10.2374 79.416 1405.963 9.599469 Height of NA =10.237 I ref =1415.56 I na =602.54 Z deck =44.44 Z keel =58.85 Z Req 43.31 m3 Here ZDECK and ZKEEL are getting more than the minimum section modulus required. So the design is satisfactory


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