Calculate the significant wave height

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Reference no: EM132443251

Assignment 1: Ocean Waves

Question 1. A jacket rig is to be designed and fixed to the sea bed. A buoy has recorded the following wave heights for the rig's operating field:

Wave Height (m)	0-2	2-4	4-6	6-8	8-10
Number of Waves	1040	1250	300	200	50

The drilling machinery is expected to be placed on the drill floor, which is located 5.5m above the mean sea level.

a) Use Rayleigh distribution to obtain the probability of the water reaching this level.

b) How will this probability change (based on Raylcigh distribution and the distribution defined by the data from the previous table if the machinery platform were to be placed at 4m above the sea level.

c) Plot the wave height histogram along with the theoretical Raylcigh Distribution

d) Calculate the significant wave height H(1/3), the H(1/10), and H(1/100) based on the wave elevation's data.

e) In your opinion, is it feasible to place the drill floor at 5.5m above the mean sea level'?

Question 2. The marine design consultancy where you work has been commissioned to design a new multi-purpose vessel for operation in open ocean conditions at the North Atlantic Ocean.

a) What possible sources would be available for identifying the wave environment that the new vessel will encounter during operations‘? Provide advantages and disadvantages of each one.

b) What idealizcd wavc spectrum would you use and why'?

c) Using the Pierson-Markowitz spectrum formulation, plot a seaway spectral density considering a significant wave height as per the table below. Select the significant wave height considering a 50-Year Return Period. Justify your decision.

Cell 110 56.75'N

Significant Wave Height Extremes oy Return Period

57 5 W Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
10 Year 10 3 10.1 9.5 7 8 6 2 S. 3 4 3 5 7.7 9 4 10 7 10.9 11.6
25 Year 11.5 11.6 10.8 8.9 7.2 6.1 4.9 5.7 9 10.7 12.3 12 12.3
Z 50 Year 12 4 12 8 11 8 g 7 7 9 6 6 5 4 6 3 10 11 7 13 4 12 9 12 g
100 Yr. 13.3 13.9 12.B 10.5 8 6 7.2 5.8 6.8 1 0.9 12 7 14.6 13.7 13.5

d) Determine the wave amplitude for each circular wave frequencies in the spectral density curve

e) Calculate ¯Tz, ¯Tp and ¯λ_w

f) Calculate the bandwidth parameter e and explain the results

Question 3. Why do you think a submarine would go deep into the ocean during a storm?

Assignment 2:

Objective: Prepare a shipbuilding cost estimate for the following new construction ship:

Ship type: Product tanker

Deadweight: 35,000 tons

Light ship weight: 14,000

tons Gross tonnage: 25,000 gt

Weight breakdown by SWBS group:

Group Title Weight (tons)

100	Structure	9,000
200	Propulsion Machinery	1,000
300	Electrical	300
400	Command & Surveillance	25
500	Auxiliary Machinery	2,000
600	Outfit	1,675

Engineering hours (group 800) = 25% of the sum of group 100 to 600 hours Support Services hours (group 900) = 50% of the sum of group 100 to 600 hours

Your estimate deliverable will have seven sections:

1. Direct labor rate: specify and explain.

2. Overhead rate: specify and explain.

3. Levels of management reserve and profit: specify and explain.

4. A well-documented Excel spreadsheet to estimate the shipyard's cost to design and build the ship and the bid price.

5. A cross check. That is, check your results using different (simpler) approaches and/or different information sources.

6. How competitive do you expect your bid will be?

7. What action(s) do you recommend to increase your competitiveness and/or profit?

Assignment 3:

Problem 1

Table 1 shows the fatigue test data, AISI 1045 steel.

a) Use linear regression to estimate the best fit to the data in log-log scale. Show the line on the same graph with the data.

b) Sketch upper and lower bounds for the data and comment on the observed scatter. Estimate the fatigue limit for the material and the fatigue strength at lx105 cycles to failure. Estimate the expected fatigue life at the stress amplitude of 175 MPa.

Stress amplitude sa Fatigue life Nit Note

[M Pal [Cycles]

130 10 000 000

130 1 750 000

130 1 600 000

130 2 330 000

130 10 000 000

150 1 860 000

150 1 100 000

150 601 300

150 485 000

170 190 567

170 465 000

170 153 140

170 311 250

185 144 430

185 152 060

185 176 960

185 116 430

220 46 240

220 52 020

220 62 SOO

220 95 000

220 65 300

245 30 100

245 38 500

245 26 300

245 29 600

Problem 2

An unnotched member fabricated from AISI 4142 steel (see table) is subjected to the load history shown below.

a) Perform a rainflow count of the load history.

b) Estimate the number of cycles and the number of (blocks) repetitions to failure. Use the Goodman mean stress correction equation.

Figure 1: Load history for one repetition.

Table 2: Constraints for stress-life curves: tests at zero mean stress on unnotched axial specimen.

Material	Yield Strength σ_n	Ultimate Strength σ_u	True Fracture Strength	σ_a = σ'_f (2N_f )^b		= A NI_J^B
Material	Yield Strength σ_n	Ultimate Strength σ_u	σ_fB	σ²f	A	b = B
(a) Steels
AISI 1015	227	415	725	976	886	-0.14
(normalized)	(33)	(60.2)	(105)	(142)	(128)
Man-Ten	322	557	990	1089	1006	-0.115
(hot rolled)	(46.7)	(80.8)	(144)	(158)	(146)
RQC-100	683	758	1186	938	897	-0.0648
(roller Q & T)	(99.0)	(110)	(172)	(136)	(131)
AIS1 4142	1584	1757	1998	1937	1837	-0.0762
(Q & T, 450 HB)	(230)	(255)	(290)	(281)	(266)
AISI 4340	1103	1172	1634	1758	1643	-0.0977
(aircraft quality)	(160)	(170)	(237)	(255)	(238)

Reference no: EM132443251

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