floatover mating and mooring analyses

Float over Mating and Mooring Analyses

DOCKWISE SHIPPING B.V.

Agenda Major Areas In Float-over Engineering

Docking and Mating Analyses

LMU and DSU Designs: Sizes, Stiffness and Specifications

Mooring Systems: Anchor and Mating Mooring Systems

Skid Beam Design and Sway Fender Design

Objectives of Float-Over EngineeringProvide Basis for Procurement and Subcontracting Activities

Confirm Float-over Systems for Safety and Adequacy

Major Areas in Float-over EngineeringDocking and Mating Analyses

Analysis Tools: Hydrodynamics Analysis WAMIT

Frequency Domain Analysis

Calculate Data Base: vessel added mass, wave damping, linear wave forces and mean drift wave forces

Motion Analysis Program MOSESTime domain simulation of vessel dynamics in random waves, using frequency domain hydrodynamic results

Capable of modeling nonlinear interactions at LMU, DSU, fenders and mooring systems


Analysis Methodology: Rigid body dynamics vessel and deck are considered rigid

bodies with 6 DOF

Time domain simulations applied in order to take into account the nonlinear forces in the system such as LMU and DSU

LMU, DSU and fenders are modeled as compression only springs with nonlinear stiffness

Structural stiffness of the deck and jacket at LMU and DSU are calculated from the SACS model, and combined with the stiffness modeling of the LMU and DSU

1-hour duration of the time domain simulation for each stage. The simulated maximum values were used for design (0.25s in entry and exit, 0.05s in mating analysis)


Critical Parameters in Modeling and Analysis:

100mm gap between barge side and fender at both sides of vessel during entry/exit

Nominal vertical clearance at LMU during entry is 1.22m (at 8.13m draft) without tide consideration

Nominal vertical clearance at DSU during exit is 0.89m (at 11.24m draft) without tide consideration

Nominal vessel under-keel clearance during exit is 2.50m (at 11.24m draft)

Pretensions in the mooring lines are around 25 MT.

LMU Modeling300mm stroke

Steel-to-steel contact at 80% of deck load

0.0

500.0

1000.0

1500.0

2000.0

2500.0

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350

Compression (m)

Rea

ctio

n (m

t)

Leg A1Leg A2Leg A3Leg A4Leg B1Leg B2Leg B3Leg B4

Major Areas in Float-over EngineeringDocking and Mating Analyses LMU and DSU Designs

DSU Modeling150mm stroke

Steel-to-steel contact at 80% of deck load

0

500

1000

1500

2000

2500

3000

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

Compression (m)

Re

act

ion

(m

t)

Stbd, Row 1Stbd, Row 2Stbd, Row 3Stbd, Row 4Port, Row 1Port, Row 2Port, Row 3Port, Row 4

Major Areas in Float-over EngineeringDocking and Mating Analyses LMU and DSU Designs

Fender ModelingType JLP800H, two 1-meter units in each fender

0

20

40

60

80

100

120

0 0.1 0.2 0.3 0.4 0.5

Compression (m)

Re

act

ion

(mt)


SELECTED ENVIRONMENTAL CRITERIA

Wave:Head/Stern Sea: Hs = 1.00 m; Tz = 5.0 secQuartering Sea: Hs = 0.75 m; Tz = 4.5 secBeam Sea: Hs = 0.50 m; Tz = 4.0 secSpectrum: P-M

Wind: Speed: 10m/s (1-hour mean at 10 m above WL) Spectrum: API wind spectrum

Current: Speed: 0.5 m/s (uniform along the depth)


Mooring System Modeling Anchor Spread MooringCatenary effect and stretch of the lines are considered

Pretensions are adjusted to balance the mean environmental loads (wind, current and mean wave drift load)


Mooring System Modeling Mating Mooring SystemCatenary effect and stretch of the lines are considered

Used to fine-tune the vessel position during entry and mating



Entry Phase Stage 1

Entry Phase Stage 2


Entry Phase Stage 3


Entry Phase Stage 4


Entry Phase Stage 5


Entry Phase Stage 6


Mating Phase Analysis CasesStage Draft

(m)Status of

LMUStatus of

DSUWave heading

(deg)Description

1 9.250Stabbing pin is 0.5 m above the receiver

0.150 m compression. Steel to steel contact 0,45,90,135,180

Before the engagement of LMU

2 9.750Stabbing pin just touches receiver

0.150 m compression. Steel to steel contact

0,45,90,135,180, 225, 270, 315

0% deck weight transfer

3 9.882 0.132 m compression0.150 m compression. Steel to steel contact

0,45,90,135,180, 225, 270, 315


4 9.966 0.210 m compression 0.144 m compression. 0,45,90,135,180, 225, 270, 315






7 10.1250.300 m compression, steel to steel contact

0.075 m compression. 0,45,90,135,180, 225, 270, 315



0.035 m compression. 0,45,90,135,180, 225, 270, 315



No compression, stabbing pin just touches receiver

0,45,90,135,180, 225, 270, 315



Mating Phase Stage 1

Mating Phase Stage 9

Analysis CasesExit Phase

Stage Draft (m)

Status of Spread Mooring

Status of Mating Mooring

Wave heading (deg)

Description

1 11.240 Lines 1, 2 active All lines active 0,45,90,135,180 Vessel at mating position

2 11.240 Lines 1, 2 active All lines active 0,45,90,135,180Stern is 65m from the centre of jecket

3 11.240 Lines 1, 2 active All lines active 0,45,90,135,180 Stern at jacket Row 1




Exit Phase Stage 1

Exit Phase Stage 2

Exit Phase Stage 3

Exit Phase Stage 4

Exit Phase Stage 5

Exit Phase Stage 6

Analysis Results Hydrodynamic AnalysisPanel Models:

Entry: Exit:

Analysis Results Hydrodynamic Analysis Data BaseAdded mass:

Analysis Results Hydrodynamic Analysis Data BaseWave

Damping

Data Base

Analysis Results Hydrodynamic Analysis Data BaseLinear Wave

Responses

Analysis Results Hydrodynamic Analysis Data BaseMean Drift

Forces

Analysis Results Time Domain Analysis (Entry)

Maximum tension in spread mooring system

Conclusion: Maximum tension in mooring lines is 96.20 ton,

Minimum safety factor is 2.36 (> 2.0 API requirement)

0 deg heading 45 deg heading 90 deg heading 135 deg heading 180 deg headingStage Max tsn

(mt)Line

Max tsn (mt)

LineMax tsn

(mt)Line #

Max tsn (mt)

Line #Max tsn

(mt)Line #

1 60.55 SPM_PF 96.20 SPM_PF 79.29 SPM_PF 62.28 SPM_PF 64.71 SPM_



4 41.81 SPM_PF 87.68 SPM_PF 72.34 SPM_PF 64.75 SPM_PF 17.48 SPM_P

5 39.47 SPM_PF 68.21 SPM_PF 66.08 SPM_PF 24.75 SPM_PF 8.64 SPM_P

6 - - - - - - - - - -

Analysis Results Time Domain Analysis (Exit)

Maximum tension in spread mooring system

Conclusions: Maximum tension in mooring lines is 99.5 ton,

Minimum safety factor is 2.27 (> 2.0 API requirement)

0 deg heading 45 deg heading 90 deg heading 135 deg heading 180 deg heading

Stage Max tsn (mt)

Line #Max

tsn (mt)Line #

Max tsn (mt)

Line #Max

tsn (mt)Line #

Max tsn (mt)

Line #

1 - - - - - - - - - -

2 69.99 MTM_SA 73.11 MTM_PA 53.08 MTM_PA 62.93 MTM_PA 60.56 MTM_

3 47.15 MTM_SA 99.48 MTM_PA 56.38 MTM_PA 72.12 MTM_PA 73.43 MTM_

4 51.56 MTM_PF 68.86 MTM_SA 62.17 MTM_SA 72.67 MTM_PF 46.40 MTM_

5 64.04 MTM_PF 35.65 MTM_PF 48.39 MTM_PF 71.97 MTM_PF 52.23 MTM_

6 44.65 MTM_PA 47.99 MTM_SA 34.78 MTM_PF 59.97 MTM_PF 51.37 MTM_

Analysis Results Time Domain Analysis (Entry)

Maximum vertical motions at LMU

Conclusion:

Minimum vertical clearance at LMU is 0.95 m during entry.

0 deg heading 45 deg heading 90 deg heading 135 deg heading 180 deg headingStage Max -Z

(m)LMU #

Max -Z (m)

LMU #Max -Z

(m)LMU #

Max -Z (m)

LMU #Max -Z

(m)LMU #

1 -0.104 A4 -0.121 A4 -0.146 A4 -0.128 A1 -0.129 B

2 -0.110 A4 -0.144 A4 -0.142 A4 -0.132 A1 -0.124 B1

3 -0.110 A4 -0.141 A4 -0.147 A4 -0.124 A1 -0.128 B1

4 -0.103 A4 -0.134 A4 -0.158 A1 -0.118 A1 -0.111 B1

5 -0.103 A4 -0.145 A4 -0.173 A1 -0.127 A1 -0.107 B1

6 -0.097 A4 -0.160 A4 -0.270 A4 -0.141 A1 -0.116 B

Analysis Results Time Domain Analysis (Exit)

Maximum load in fenders

Conclusion: Maximum load at fender is 121.8 ton, which will not affect the

structural integrity of the jacket

Maximum compress of the fender is 0.25m, less than the design allowable of 0.4m

0 deg heading 45 deg heading 90 deg heading 135 deg heading 180 deg headingStage Max load

(mt)Fender location

Max load (mt)

Fender location

Max load (mt)

Fender location

Max load (mt)

Fender location

Max load (mt)

Fender location

1 0 - 0 - 0 - 0 - 0 -

2 0 - 119.77 A4 99.97 A4 83.25 A4 0 -

3 0 - 119.33 A3 120.52 A4 102.92 A4 0 -

4 0 - 115.82 A4 121.77 A4 106.07 A4 0 -

5 0 - 120.39 A4 121.86 A4 119.88 A4 0 -

6 0 - 71.17 A4 110.16 A4 46.81 A14 0 -

Analysis Results Time Domain Analysis (Mating)

Maximum Horizontal Offset of the LMU Stabbing Pins before Engagement

Conclusion: Maximum horizontal excursion of the LMU stabbing cone is 0.3m,

less than the design allowable of 0.4m.

0 deg heading

45 deg heading

90 deg heading

135 deg heading

180 deg heading

Offset @ A1 (m) 0.134 0.273 0.281 0.168 0.114

Offset @ A2 (m) 0.134 0.272 0.291 0.170 0.114

Offset @ A3 (m) 0.134 0.276 0.302 0.173 0.114

Offset @ A4 (m) 0.134 0.290 0.313 0.189 0.114

Offset @ B1 (m) 0.134 0.233 0.278 0.185 0.114

Offset @ B2 (m) 0.134 0.232 0.288 0.187 0.114

Offset @ B3 (m) 0.134 0.237 0.299 0.188 0.114

Offset @ B4 (m) 0.134 0.253 0.310 0.189 0.114


Maximum Loads at the LMUs during Mating:

Max load in longitudinal direction: 222 tons

Max load in transverse direction: 339 tons

Max vertical load at one pile top: 3331 tons

Jacket structural integrity shall be checked with the above calculated maximum loads.


Maximum Loads at the DSUs:

Max load in longitudinal direction: 169 tons

Max load in transverse direction: 377 tons

Max load in vertical directions: 3105 tons

Jacket structural integrity shall be checked with the calculated maximum loads.

Analysis Results Time Domain Analysis

Summary of Mooring System Results:

Maximum tension in spread mooring lines is 99.5 ton (meet design criteria)

Maximum tension in mating mooring lines is 66 ton (meet design criteria)

Maximum load on fenders is 61 tons, Maximum fender compression is 0.25m

Minimum vertical clearance between the deck and barge in exit phase is 0.75m

Minimum under-keel clearance is 2.2m

Major Areas in Float-over EngineeringMooring System Design

Scope:Stand-off analyses

Entry / mating / exit

Quality Checks:Comparison MOSES and AQWA

Basic hydrodynamic data

Mooring simulations

Float-over Entry Phase

Fender jacket-leg row 4Jacket center origin at still waterline


Anchor locations

Buoy present in all mooring lines

buoy

line-grounding


Analyses in AQWA Limits:

Head-seas Hs= 2.5 m

Quart. Seas Hs= 1.5 m

Beam seas Hs= 1.0 m

Squall:Vwind = 24 m/s

tug assistance required

Buoys not to scale

Basis for Stand-off Condition Calculations

Major Areas in Float-over EngineeringSway Fender Design

Sway Fender Designs

Layout:2 rubber blocks Fenderboard for contact

area with rub-rails at different draftsRubber blocks bolted on

foundations

foundationfenderboard

Rubber block

Major Areas in Float-over EngineeringSkid Beam Design

Design SummaryLayout:2 types, inner rows higher load than outer rows.

Deck support points 5 m from vessel side

Limiting skid shoe length 10 m.

To spread loads sufficiently 2 skid tracks per skid-shoe.

On-shore 1 skid track available. Transition of skid tracks in link-beam design.

Inner row

Outer row On-shore skid-shoe

floatover mating and mooring analyses

Documents