Calculation of Section_modulus

The loss of the Derbyshire Project NA 240A

 Appendix

Section modulus calculations for stiffeners and girders Requirements are based on the class rules from Det Norske Veritas b

Original design

Toppflange

Longitudinal stiffeners

t

Toppflange eff eff breadth b e

Neutral axis W eb

t

Input

h

63 cm

Toppflange thickness t

1.05 cm cm

Web height h

63.5 cm

Web thickness t

1.05 cm

Bottom flange flange bredth b

28 cm

Bottom flange thickness t

2.5 cm cm

z 

S

xiAi

6772 cm

S

Ai

202.8 cm

 Neutral axis  z 

Flange

33.4 33.4 cm

t b

161875 cm 4809 cm

Moment of inertia Section Modulus  Z 

4

Design rules

Effective flange of the girder: be = 0.84 b (DnV Part 3, Ch 7 Sec 3 C400) Effective flange of the stiffners: b e = 60 * t (web)

Sp a n l

3.68 m

Spacing b

0.994 m

Design pressure

17.17 kN/m 204 cm

Required Z

Original design Side girder

Original design Input

Center girder

Input

Toppflange breadth b

368 cm

Toppflange breadth b

368 cm

Toppflange thickness t

1.05 cm

Toppflange thickness t

1.05 cm

Web height h Web thickness t

56 cm

Web height h

1.05 cm

Web thickness t

91 cm 1.05 cm

Bottom flange bredth b

10 cm

Bottom flange bredth b

7.5 cm

Bottom flange thickness t

2.5 cm cm

Bottom flange thickness t

2.5 cm cm

3

S

xiAi

20983 cm

S

xiAi

35128 cm

S

Ai

408.4 cm

S

Ai

438.9 cm

 Neutral axis  z  Moment of inertia Section Modulus  Z 

 Neutral axis  z 

51.4 51.4 cm 4

119703 cm 2330 cm

Moment of inertia Section Modulus  Z 

Design rules Sp a n l Spacing b Design pressure Required Z

2

3

80.0 80.0 cm 340239 cm 4251 cm

4

Design rules 11 m

Span l

3.68 m 17.17 kN/m 8133 cm

Spacing b 2

Design pressure Required Z

11 m 3.68 m 17.17 kN/m 8133 cm

2

1

The loss of the Derbyshire Project NA 240A

 Appendix

Original design, 14.72 m span Longitudinal stiffener

Faulkner's design Input

Toppflange eff breadth be

Transverse stiffener

Input

Toppflange eff breadth be

63 cm

63 cm

Toppflange thickness t

1.05 cm

Toppflange thickness t

1.05 cm

Web height h

63.5 cm

Web height h

63.5 cm

Web thickness t

1.05 cm

Web thickness t

1.05 cm

Bottom flange bredth b

28 cm

Bottom flange bredth b

28 cm

Bottom flange thickness t

2.5 cm

Bottom flange thickness t

2.5 cm

S

xiAi

6772 cm

S

Ai

202.8 cm

 Neutral axis  z  Moment of inertia Section Modulus  Z 

3

4

6772 cm

S

Ai

202.8 cm

Moment of inertia Section Modulus  Z 

Design rules 14.72 m

Spacing b

0.994 m 17.17 kN/m

Required Z

3265 cm

2

Our suggestion

11 m

Spacing b

0.981 m

Design pressure

17.17 kN/m

Required Z

2168 cm

2

Our suggestion Input

Longitudinal stiffeners

Toppflange breadth b

368 cm

Toppflange eff breadth be

Toppflange thickness t

1.05 cm

Toppflange thickness t

Web thickness t

4

161875 cm 4809 cm

Span l

Design pressure

Web height h

33.4 cm

Design rules

Span l

All girders

xiAi

 Neutral axis  z 

33.4 cm 161875 cm 4809 cm

3

S

90 cm

Web height h

1.05 cm

Web thickness t

Input 63 cm 1.05 cm 20 cm 1.05 cm

Bottom flange bredth b

30 cm

Bottom flange bredth b

7.5 cm

Bottom flange thickness t

2.5 cm

Bottom flange thickness t

1.5 cm

S S

xiAi Ai

 Neutral axis  z  Moment of inertia Section Modulus  Z 

34776 cm 494.1 cm

2

4

Spacing b Design pressure Required Z

1707 cm

S

Ai

98.4 cm

Moment of inertia Section Modulus  Z 

Design rules Span l

xiAi

 Neutral axis  z 

70.4 cm 625275 cm 8883 cm

S

2

17.3 cm 4

5691 cm 328 cm

Design rules 11 m

Span l

3.68 m 17.17 kN/m 8133 cm

2

3.68 m

Spacing b

0.994 m

Design pressure

17.17 kN/m 204 cm

Required Z

2

2