Scantling Calculation

Scantling Calculation

Midship section modulus required

= 11.00

Required Section Modulus = 87128061.02 87.13 a. Main Deck Plating

Thickness (t) = 0.001*S1*(0.059*L1+7)√(Fdk/FL)

S1 =s = Stiffener Spacing = 700 mm

L1=L - Rule Length in meters on the summer LWL 314.5 m

kL = higher tensile factor = 245/σ or 0.72 = 1.00 (235N/mm2)

kL for Mild Steel = 1.0

Fdk = 1.0

Thickness of main deck plating t = 13.28 mm

Adding Corrosion allowance t = 11 mm

Stringer plate thickness to be increased by 2% 13.2 mm

t = 14 mm

Deck Longitudinals

a. Main deck (Pt4. Ch1, Table 1.4.3)

= 1567.60

lc = Effective Length of stiffening members 6.6 m K = a factor depend on the freeboard

= 22.6*L1 * C1/1780-L1 = 4.850

C1 = 810 /(2450 - 1640*Fd) = 1

206.12

h2 = Cargo Head = 1 m

lc = Effective Length of stiffening members = 6.6 m

Shell Envelope Plating (As per LRS Pt4,Ch1, 1.5.1) a. Plate Keel

Breadth b = 70 x B …mm = 3640 mm

(But not to be taken less than 750mm nor greater than 1800mm)

= 1800 mm

Thickness t == (t1+2) 17 mm

Where t1 is the adjacent bottom shell thickness 15 mm b. Bottom Shell and Bilge Plating (Pt 4 Ch1 1.5.2)

Thickness greater of the following

i) t = 0.001 S1 (0.043*L1+10) √(Fb/KL) = 16.47 mm t = 15 mm Fb =KL = 1 Z = C₁ * L2 _*B(C B + 0.7)……... cm3 C₁ = 10.75 - (350-L/100)1.5 Z_{o cm}3 m3 Z = 0.0106 *s *k* l_c2 _cm3 Z = s *k*(5.9*L1+25*h₂* l_c2_)*10-4 _cm3

c.Side shell (Pt4, Ch1.5.3)

i) Side shell clear of Shear Strake Greater of the following

a) above D/2 from base 13.29

1) t = 0.001 S1 (0.059L1 +7)*√(Fd/KL) = 17.89 mm

= 15.34 mm

t = 14 mm

b) At upper turn of hopper tank the greater of the following

i) t = 0.001 S1 (0.059L1 +7) *√Fd/KL = 17.89 mm

t = 15 mm

ii)Shear Strake

the greater of the following 14.82

t = 0.001 S1 (0.059L1 +7) *√Fd/KL = 17.89 mm t = 0.00083*S1(√LK)+2.5 = 11.76 mm t = 13 mm a.Bottom Longitudinals = 4670.173 k3 = 1.11*T1*c2 = 14.449

T1 = T but not to be taken less than 0.6 & need not be taken less than 0.8D

T1 = 21.6

C2 = a factor varying from 1.0 at D/2 to 910/(2550-1040Fb) at bottom

C2 = 0.60

b.Side Longitudinals i) Side Longitudinal above D/2

= 494.44

ρ = 1.03

b = 1.4 for rolled or builtup section i) Side Longitudinal below D/2

= 4670.17

c.Bilge Longitudinals

Stiffener Spacing s = 850 mm

= 5670.92

Double bottom Structure (As per LRS pt4, Ch8, 7.2) a) Floors

Thickness (t) =6.0+0.03L = 15.44 mm

t = 14 mm

b)Duct Keel (Pt4, Ch1, 8.3.7)

Thickenss of Side Plates t = (0.008 dbh +2)√k = 18 mm

dbh = Double bottom height = 2000 mm

t = 18 mm

The sides of the duct keel are to be spaced not more than 2m apart c)Watertight Side Girders (Pt4, Ch1, 8.3.5)

t = (0.0075*dbh+2)√k = 17 mm

t = 17 mm

d)Inner bottom plating and Stiffening (Pt4, Ch1, 8.3.1)

= 16.47 mm

Bottom plate stiffener Spacing s = 700 mm

t = 14 mm

e)Margin Plate

If fitted t = 20% greater than the inner bottom plating

t = 17 mm Z = 0.0106*S*k*lc2 _{*k3 cm}3 Z = (0.0113*ρ*s*k*b*lc2_{) cm}3 t/m3 Z = (0.0106*s*k*k3*lc2_{) cm}3 Z = (0.0106*s*k*k3*lc2_{) cm}3 t = 0.00136*(s+660)*(k2_LT)1/4

Bulkheads (Pt4, Ch1, 1.9.1) For deep tank bhds

t = 0.004*s* sqrt (s*h4*k/1.025) +2.5 mm= 10.35 mm

Inner shell longtl. Spacing s = 700 mm

h4 = 11.5 m

t = 11 mm

Summary

S.No. Item Thickness (mm)

1 Main deck plating 11

3 Stringer plate 14

5 Keel Plate 17

6 Bottom Shell plate 15

7 Bilge Plate 15

8 Side shell plate 14

9 Shear Strake 13

10 Floors 14

11 Duct Keel 18

12 Water tight Side Girders 17 13 Inner bottom Plate 14

14 Margin (If reqd) 17

15 Inner shell plate 11

h4 = for WT bhd plating, the distance from a point of the height of the plate above its lower edge to the top of the tank or half the distance to the top of the overflow whichever is greater

Midship Section Modulus Calculation Ref: Assumed Neutral Axis at 10m above BL

Depth above NA = 24 m 2400 cm

Depth below NA = 10 m 1000 cm

Breadth of the Ship = 52 m 5200 cm

Breadth of the Stringer Plate = 5.2 m 520 cm

Breadth of the keel plate = 1.8 m 180 cm

Breadth of the Bottom Sheel plate = 50.2 m 5020 cm

Height of Double bottom = 2 m 200 cm

S.No Item QTY Lever (m) Lever (m)

Above NA 1 Main deck Plt 1 4576 24 109824 24 2635776 2 Stringer Plate 2 1456 24 34944 24 838656 4 Side shell plt 2 6720 12 80640 12 967680 5 Bulkhead Plate 3 7920 12 95040 12 1140480 320448 5582592 6285312.1 Below NA 1 Keel Plate 1 306 10 3060 10 30600 2 Bottom Shell 2 15060 10 150600 10 1506000 3 Side shell plt 2 2800 5 14000 5 70000 4 Bulkhead Plt 3 3300 5 16500 5 82500 5 Inner bottom plt 1 252 8 2016 8 16128 6 Duct keel plt 2 720 9 6480 9 58320 7 WT Side Girders 4 1360 9 12240 9 110160 44470 204896 1873708 1980701.6

Shift in Neutral Axis = Ist Moment ANA -Ist Moment BNA/Total Area

= 2.60 m

Moment of Inertia of ANA 8266013.7

Location of Actual NA = 12.60 m

Using Parallel Axis Theorem

= 7965760.39

= 796.58

Section Modulus at Bottom Zb = 63.23

Section Modulus at Deck Zd = 89.11

Hence the available Section Modulus is more than the required, the design is safe

Shear Force and Bending Moment Table (From Trim and Stability Booklet)

S.No. Loading Conditions

1 Ballast Arrival Condition with 10% Stores 3663.3 41308.7

2 Ballast Departure Condition with 100% Stores 3422.6 60383.4

3 Fully Loaded Departure with 100% Stores 3422.6 60383.4

Yield stress of Steel fs = 235

Allowable Bending Stress (fab =0.6 fs) fab = 141

Maximum Bending Stress at Deck (fb = M/zd) fb = 54.13

Maximum Bending Stress at Btm (fb = M/zb) = 38.4

The actual Bending Stress is lesser than the allowable bending stress hence the design is safe Area (cm2₎ Ist Moment (cm2 _m) 2nd M.I (cm2 m) I_ANA = _cm2 _m2

I_NA = I_ANA - Area * Shift2 _{cm2 m2}

I_{NA m}4 m3 m3 Bending Moment (MN.m) Shear Force (kN) N/mm2 N/mm2 N/mm2 N/mm2

0.05 0.02 322560.0 380160.0 702720.1 0.0074 0.2824 23333.3 27500.0 0.0041 19440.0 36720.0 106993.6 I_own (cm2 _m2₎