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Python代写-FY20/21

时间：2021-03-16

FY20/21: Offshore Engineering and Analysis Station Keeping and Structures Assignment

B. Thornton DUE: 23:00 Ma rch 18, 2021

Stationkeeping and Structures Assignment

This individual assignment is worth 10% of your final grade. Submit your answers and supporting

material via Turnitin on blackboard by the deadline.

Submission format: Maximum 4 page PDF report and supplementary material

• PDF report: Your report should consist of:

o Method: Equations used, description of any assumptions and their justification

o Results: Figures and tables that illustrate your main results

o Discussion: Description of your results, their implications and your recommendations

• Supplementary material: Separate file(s) with working annotated codes or spreadsheets used in

your calculations. This doesn’t count towards your page limit.

Marking criteria: The PDF report is marked based on how you use the concepts taught in the module to

complete the assignment. Only aspects explained in the PDF report get marks. “See code for method” in

the PDF report isn’t a satisfactory explanation and will get no marks. You can organize the document as

you see fit. If you use values from design regulations, course notes or papers, please cite them.

Inidicative marks for each task are shown as [20 marks].

Category Classification (Fail)

0-40

Unsatisf

actory

(3rd)

40-50

Adequat

e

(2.2) 50-

60

Fair

(2.1)

60-70

Good

(1st)

70-100

Outstand

ing

Methods Appropriate choice

and correct

implementation of

method. Description

of assumptions, their

justification and/ or

implications

Analysis and

interpretation

Documentation of

results. Relevance of

analysis and discussion

Presentation Structure,

Language and

communication,

Figures, tables,

Referencing

Late penalty is 10% per day. For exceptional circumstances please see special considerations:

http://www.southampton.ac.uk/quality/assessment/special_considerations.page

FY20/21: Offshore Engineering and Analysis Station Keeping and Structures Assignment

B. Thornton DUE: 23:00 Ma rch 18, 2021

Consider a floating platform with 20m diameter that is pretensioned using four identical steel mooring

chains, each of length 800m with a mass of 300kg/m in air. The lines are evenly distributed, attached to

the outside of the platform at the waterline. Each line is pretensioned to 1200kN along the line at the

platform. The water depth h is 100m. The other ends are fixed using drag anchors.

• Task 1: Determine the horizontal pretension on a line, and the horizontal distance to its anchor.

Plot the catenary shape for the pretensioned condition. [2 marks]

• Task 2: Consider a 100 year maximum environmental load of 3000kN aligned with one of the

mooring lines. What’s the excursion from the pretensioned equilibrium point? Plot the catenary

of the loaded line and its opposing (relieved) pair. Will the loaded anchor get lifted? [4 marks]

• Task 3: Plot the platform’s watch circle diameter as it experiences a mean environmental load of

500kN from all angles (assume torque to be zero). If you have assumed constant pretension,

comment of how the watch circle will change if an iterative solver was used. [7 marks]

• Task 4: For the 100 year load condition in Task 2, use Gobat’s simple method to estimate the

dynamic tension in the most loaded line:*

The equivalent diameter of the chain is D=0.20 m. Assume a line vertical drag coefficient is

C’d=0.75, unloaded added mass Mo=26000 kg, added mass of lifted line per unit length

Ma= -5 kg/m. The root mean squared (rms) vertical dynamics have values = 1.3 m/s2 and

|| = 2.3 m

2/s2 respectively with a period of 11.4s.

Use a standard SN-curve for steel to determine the cumulative damage ratio for ~50 years

operation, assuming the maximum dynamic load condition occurs for 5 weeks during that

period, and the rms dynamic load _ = 0.06 with a 3s period at all other times. Which

component causes more damage? What other factors could impact line survivability? [7 marks]

*NB: If you did not complete task 2, make sensible assumptions for the mean line tension and catenary

length, S, and use those in task 4.

[Total out of 20 marks]

∆ =

− ℎ

ℎ

= (0 +

∆

) (1 + ∆) +

1

2

′∆hD ||

学霸联盟

B. Thornton DUE: 23:00 Ma rch 18, 2021

Stationkeeping and Structures Assignment

This individual assignment is worth 10% of your final grade. Submit your answers and supporting

material via Turnitin on blackboard by the deadline.

Submission format: Maximum 4 page PDF report and supplementary material

• PDF report: Your report should consist of:

o Method: Equations used, description of any assumptions and their justification

o Results: Figures and tables that illustrate your main results

o Discussion: Description of your results, their implications and your recommendations

• Supplementary material: Separate file(s) with working annotated codes or spreadsheets used in

your calculations. This doesn’t count towards your page limit.

Marking criteria: The PDF report is marked based on how you use the concepts taught in the module to

complete the assignment. Only aspects explained in the PDF report get marks. “See code for method” in

the PDF report isn’t a satisfactory explanation and will get no marks. You can organize the document as

you see fit. If you use values from design regulations, course notes or papers, please cite them.

Inidicative marks for each task are shown as [20 marks].

Category Classification (Fail)

0-40

Unsatisf

actory

(3rd)

40-50

Adequat

e

(2.2) 50-

60

Fair

(2.1)

60-70

Good

(1st)

70-100

Outstand

ing

Methods Appropriate choice

and correct

implementation of

method. Description

of assumptions, their

justification and/ or

implications

Analysis and

interpretation

Documentation of

results. Relevance of

analysis and discussion

Presentation Structure,

Language and

communication,

Figures, tables,

Referencing

Late penalty is 10% per day. For exceptional circumstances please see special considerations:

http://www.southampton.ac.uk/quality/assessment/special_considerations.page

FY20/21: Offshore Engineering and Analysis Station Keeping and Structures Assignment

B. Thornton DUE: 23:00 Ma rch 18, 2021

Consider a floating platform with 20m diameter that is pretensioned using four identical steel mooring

chains, each of length 800m with a mass of 300kg/m in air. The lines are evenly distributed, attached to

the outside of the platform at the waterline. Each line is pretensioned to 1200kN along the line at the

platform. The water depth h is 100m. The other ends are fixed using drag anchors.

• Task 1: Determine the horizontal pretension on a line, and the horizontal distance to its anchor.

Plot the catenary shape for the pretensioned condition. [2 marks]

• Task 2: Consider a 100 year maximum environmental load of 3000kN aligned with one of the

mooring lines. What’s the excursion from the pretensioned equilibrium point? Plot the catenary

of the loaded line and its opposing (relieved) pair. Will the loaded anchor get lifted? [4 marks]

• Task 3: Plot the platform’s watch circle diameter as it experiences a mean environmental load of

500kN from all angles (assume torque to be zero). If you have assumed constant pretension,

comment of how the watch circle will change if an iterative solver was used. [7 marks]

• Task 4: For the 100 year load condition in Task 2, use Gobat’s simple method to estimate the

dynamic tension in the most loaded line:*

The equivalent diameter of the chain is D=0.20 m. Assume a line vertical drag coefficient is

C’d=0.75, unloaded added mass Mo=26000 kg, added mass of lifted line per unit length

Ma= -5 kg/m. The root mean squared (rms) vertical dynamics have values = 1.3 m/s2 and

|| = 2.3 m

2/s2 respectively with a period of 11.4s.

Use a standard SN-curve for steel to determine the cumulative damage ratio for ~50 years

operation, assuming the maximum dynamic load condition occurs for 5 weeks during that

period, and the rms dynamic load _ = 0.06 with a 3s period at all other times. Which

component causes more damage? What other factors could impact line survivability? [7 marks]

*NB: If you did not complete task 2, make sensible assumptions for the mean line tension and catenary

length, S, and use those in task 4.

[Total out of 20 marks]

∆ =

− ℎ

ℎ

= (0 +

∆

) (1 + ∆) +

1

2

′∆hD ||

学霸联盟