iso phase 2 benchmarking...figure 8: iso predicted v-h envelope for the super gorilla - sand...

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File: l25217-r3 - iso validity check for super gorilla.doc

Noble Denton Consultants Ltd trading as GL Noble Denton Registered in England No. 5513434 Registered Office: Noble House, 39 Tabernacle Street, London, EC2A 4AA, UK

Distribution: ISO Committee Company: ABS Attn: Mr John Stiff Attn: W/S No: 05-130553 CTR 0

REPORT

ISO PHASE 2 BENCHMARKING

ISO 19905-1 (DIS)

VALIDITY CHECK

LETOURNEAU SUPER GORILLA CLASS

Report No: L25217 , Rev 3 , Dated 27-01-2011

The assessment has used adjusted leg-to-hull connection stiffness and other generic parameters of LeTourneau Super Gorilla jack-up units. The results presented herein are for the purposes of benchmarking alone and are not

representative of LeTourneau Super Gorilla Class jack-up units.

PHASE 2 BENCHMARKING ISO 19905-1 (DIS)

VALIDITY CHECK FOR LETOURNEAU SUPER GORILLA

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Report No: L25217 , Revision: 3, Dated: 27th January 2011

File: L25217-R3 - ISO Validity check for Super Gorilla.doc

REVISION DETAILS

Revision Date Description Author Checker Approver

0 1st Oct 2010 Draft for Internal Review ARM MLH MJRH

1 3rd Oct 2010 Initial Issue to ISO committee for comment ARM MLH -

2 19th Nov 2010 Update for initial comments ARM MLH MJRH

3 27th Jan 2011 Updated for LeTourneau comments MLH ARM RWPS

DESCRIPTION OF CHANGES

Revision Section Change

1 Various General formatting and tabulation

2 4.6 / 5.12 Correction to overturning checks

2 4.6.8 Inclusion of pinions in holding system strength checks

2 4.6.9 Correction to chord utilisations

3 1.2, 3.1.3, Tables 4-29, 5-16 & 5-17

Inclusion of wording re: artificial leg-to-hull stiffness used for benchmarking assessment

INSERTED DOCUMENT/FILE REGISTER

Path and Filename Details of File



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CONTENTS

SECTION PAGE

1 EXECUTIVE SUMMARY 7

2 SCOPE OF WORK 8

2.1 INTRODUCTION 8 2.2 SCOPE OF WORK 8 3 SITE SPECIFIC ASSESSMENT OF THE SUPER GORILLA 10

3.1 GENERAL 10 3.2 ASSESSMENT CONDITION 12 3.3 RIG DATA 12 3.4 SITE DATA 13 3.5 METOCEAN DATA 13 3.6 MINIMUM HULL ELEVATION CHECK 14 3.7 GEOTECHNICAL AND GEOPHYSICAL DATA 14 3.8 LEG LENGTH RESERVE CHECK 15 3.9 LEG AND SPUDCAN BUOYANCY 15 3.10 HYDRODYNAMIC COEFFICIENTS 16 4 ALIGNMENT POINTS AND COMMENTS 21

4.1 GENERAL 21 4.2 ALIGNMENT POINT 1 - GEOTECHNICAL CALCULATIONS 21 4.3 ALIGNMENT POINT 2 - OVERALL SYSTEM CHECKS 26 4.4 ALIGNMENT POINT 3 - ENVIRONMENTAL LOADINGS 31 4.5 ALIGNMENT POINT 4 - STICK MODEL RESPONSES 36 4.6 ALIGNMENT POINT 5 - FINAL ASSESSMENT RESULTS 41 5 ISO / SNAME COMPARISON 46

5.1 INTRODUCTION 46 5.2 FOUNDATION INPUT PARAMETERS 46 5.3 NATURAL PERIODS 47 5.4 SWAY STIFFNESS 47 5.5 WIND LOADS 48 5.6 WAVE LOADS 49 5.7 DYNAMIC AMPLIFICATION FACTORS (DAF’S) 50 5.8 INERTIA LOADSETS 51 5.9 TOTAL QUASI-STATIC LOADING 52 5.10 UTILISATION CHECKS 56 5.11 CONCLUSION 58

REFERENCES 61



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FIGURES

Figure 1 Flow chart for the overall assessment 11

Figure 2: Chord section axes system 19

Figure 3: 3 Stick Leg Model (showing hull beam grillage) 28

Figure 4: F.E. Model of Hull/Leg Interface 28

Figure 5 Unfactored DAF vs storm heading 34

Figure 6: ISO predicted leg penetration resistance curves for the Super Gorilla - SAND assessment case 62

Figure 7: SNAME predicted leg penetration resistance curves for the Super Gorilla - SAND assessment case 63

Figure 8: ISO predicted V-H Envelope for the Super Gorilla - SAND assessment case 64

Figure 9: SNAME predicted V-H Envelope for the Super Gorilla - SAND assessment case 65

Figure 10: ISO predicted ultimate capacities and fixities for the Super Gorilla - SAND assessment case 66

Figure 11: ISO predicted ultimate capacities and fixities for the Super Gorilla - SAND assessment case 67

Figure 12: ISO Predicted leg penetration resistance curves for the Super Gorilla - CLAY assessment case 68

Figure 13: SNAME Predicted leg penetration resistance curves for the Super Gorilla - CLAY assessment case 69

Figure 14: ISO predicted V-H Envelope for the Super Gorilla - CLAY assessment case 70

Figure 15: SNAME predicted V-H Envelope for the Super Gorilla - CLAY assessment case 71

Figure 16: ISO predicted ultimate capacities and fixities for the Super Gorilla - CLAY assessment case 72

Figure 17: SNAME predicted ultimate capacities and fixities for the Super Gorilla - CLAY assessment case (Including SAGE effects) 73



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TABLES

Table 3-1 Assessment Situations of the Unit 12

Table 3-2 Assembled Rig Data 12

Table 3-3 Assembled Site Data 13

Table 3-4 Assembled Metocean Data 13 [1]

Table 3-5 Hull Elevation Check 14

Table 3-6 Assembled Foundation Data 14

Table 3-7 Leg Length Reserve Check 15

Table 3-8 Leg & Spudcan Buoyancy 15

Table 3-9 Hydrodynamic Surface Condition Levels 16

Table 3-10 Hydrodynamic Leg Sections for Site 1 (sand) 16

Table 3-11 Hydrodynamic Leg Sections for Site 2 (clay) 17

Table 3-12 Member details for hydrodynamic calculations 17

Table 3-13 Base Hydrodynamic Coefficients for Tubulars 18

Table 3-14 Chord hydrodynamic coefficients 19

Table 3-15 Equivalent Hydrodynamic Coefficients for Stick Leg Model 20

Table 4-1 Summary of Site 1 (sand) assessment key inputs and outputs from analyses 21

Table 4-2 Summary of Site 2 (clay) foundation key inputs and outputs from analyses 23

Table 4-3 Leg Length Reserve Check 26

Table 4-4 Wind Area Calculations (m ) 26 2

Table 4-5 Equivalent Hydrodynamic Coefficients for Stick Leg Model 27

Table 4-6 Natural Periods (Max hull weight = 19 394 tonnes) 29

Table 4-7 Hull Displacements and Sway Stiffness 30

Table 4-8 Footing reactions from gravity loadcase 30

Table 4-9 Wind Loads 31

Table 4-10 Wave / Current Loads (LF=1,15) 32

Table 4-11 Summary of actions considered 32

Table 4-12 DAF from varying storm durations for 90 degree loading 33 R

Table 4-13 DAF from the Dynamic MPME for 60, 90 & 120-degree loading 33 R

Table 4-14 DAF from the Dynamic MPME for 15 & 45 degree loading (SAND only) 34 R

Table 4-15 DAF from the Dynamic MPME (Hull Weight = 19394,0t) 35 R

Table 4-16 DAF from the Dynamic MPME (Hull Weight = 17290t) 35 R

Table 4-17 Wind Loads (LF=1.15) 36

Table 4-18 Inertia Loads (LF=1.15) 37

Table 4-19 Total Loading (LF=1.15) 37

Table 4-20 Hull Sways (m) 37

Table 4-21 Footing Reactions 38

Table 4-22 Reactions in leg below chock (SAND) 39



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Table 4-23 Reactions in leg below chock (CLAY) 40

Table 4-24 Footing Reactions from the Global Responses (Site: SAND; Units: MN) 41

Table 4-25 Footing Reactions from the Global Responses (Site: CLAY; Units: MN) 42

Table 4-26 Member Checks (Hull weight = 19394t) 42

Table 4-27 Maximum Utilisations of the Chocks 43

Table 4-28 Maximum Utilisations of the Pinions 43

Table 4-29 Final assessment results 44

Table 5-1 Foundation parameters 46

Table 5-2 Natural periods 47

Table 5-3 Displacements and sway stiffness 47

Table 5-4 Wind loads 48

Table 5-5 Wave / Current Loads 49

Table 5-6 Dynamic amplification factors (DAFs) 50

Table 5-7 Weighted average DAFs 50

Table 5-8 Inertia loadset 51

Table 5-9 Total quasi-static loading 52

Table 5-10 Hull sway 52

Table 5-11 Reactions in leg at base of rack chock - Maximum Hull Weight 53

Table 5-12 Reactions in leg at base of rack chock - Minimum Hull Weight 53

Table 5-13 Reactions at base of leg - Maximum Hull Weight 54

Table 5-14 Reactions at base of leg - Minimum Hull Weight 54

Table 5-15 Overall loading summary 55

Table 5-16 Final assessment results Site 1 (Sand) 56

Table 5-17 Final assessment results Site 2 (Clay) 56

Table 5-18 Differences between ISO and SNAME 59



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1 EXECUTIVE SUMMARY 1.1 The purpose of this work is to undertake a complete run through of the entire Draft

International Standard (DIS) ISO 19905-1 and to make numerical comparisons to ensure that the results obtained are on reasonable compliance with the results from a similar analysis to the SNAME bulletin 5-5A (Ref [1]), as “Phase 2” benchmarking of the proposed ISO 19905-1 DIS (Ref [2]) document used for Site Specific Assessment of Mobile Offshore Units.

1.2 This analysis has been designed to check the validity of the ISO 19905-1 DIS results through the study of a typical jack-up design, LeTourneau Super Gorilla class unit using adjusted leg-to-hull connection stiffness values. Assessment has been completed for two foundation conditions, comparing to SNAME bulletin 5-5A (Ref [1]) following the completeness check undertaken in “Phase 1” benchmarking (Ref [3]). It is noted that because the assessment has used adjusted leg-to-hull connection stiffness values, the results presented are for the purposes of benchmarking alone, and are therefore not representative of the Super Gorilla.

1.3 This analysis using the entire ISO 19905-1 DIS document included the initial steps of; overall considerations, assembling the data, determining the analysis methods at different stages, finite element (FE) modelling, response analyses and the final assessment of structural strength of leg members and foundation capacities, etc. Excel spreadsheets, generally recognised commercial FE software PAFEC and two in-house programs, the analytical tool JUSTAS and the PAFEC-based FE programme FORCE-3, have been used to assist the analysis.

1.4 For each step, both input and output data are explicitly presented and the methods applied are extensively explained so that the entire process of the analysis can be followed and repeated. The intermediate results from each step are cross-checked with the co-workers from the ISO committee before continuing to the next step. Any discrepancy is reported and the reasons are explained.

1.5 The ISO assessment results are compared to assessment results based on SNAME bulletin 5-5A (Ref[1]), presented in Section 5.

1.6 Comments relating to the ISO document regarding errors, omissions and ambiguities are included in Appendix A

1.7 The results from this assessment show that assessment using the ISO 19905-1 approach has been found to be valid with utilisation checks similar in magnitude and slightly less onerous for the site 1 (sand) assessment and marginally more onerous for the site 2 (clay) assessment condition when compared to SNAME.



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2 SCOPE OF WORK

2.1 INTRODUCTION

2.1.1 GL Noble Denton has been instructed by ABS, on behalf of the ISO committee, to carry out the phase 2 benchmarking of the ISO 19905-1 “Petroleum and natural gas industries - Site-specific assessment of mobile offshore units - Part 1: Jack-Ups” (Draft Industry Standard) (ISO) (Ref [2]) which has been developed from SNAME bulletin 5-5A (Ref [1]).

2.1.2 The phase 2 benchmarking process involves the completion of a full site assessment analysis, running through the entire standard to check that the document is not only complete but that the specified methodology will yield reasonable and useful results. A comparison is also made with SNAME bulletin 5-5A Rev 3 (Ref [1]) from which the ISO document is derived. The intermediate results from each stage of the analysis have been checked against those calculated by Global Maritime, who have performed an identical analysis. Any differences have been resolved prior to recommencement of the analysis.

2.1.3 All questions which arose during the work and any clauses which caused doubt as to the exact methodology to follow are identified in the report with appropriate comments and the decisions which were made such that the analysis could be continued.

2.1.4 For the purpose of the benchmarking work, the use of in-house specialist programs normally used in routine assessment work have been avoided where possible with the results presented in open-format calculations, tables and graphs.

2.2 SCOPE OF WORK

2.2.1 The purpose of this work is to provide a validity check of the proposed ISO 19905-1 (DIS) (Ref [2]) document used for Site Specific Assessment of Mobile Offshore Units.

2.2.2 To perform this analysis a typical jack-up, location and metocean conditions were selected as shown below:

Jack-Up LeTourneau Super Gorilla Class unit.

Location A typical sand foundation condition (Site 1)

A typical clay foundation condition (Site 2)

Metocean A 50-year extreme storm conditions based on operations manual design storm condition .



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2.2.3 The analysis following the ISO document has been divided into 5 alignment points for step by step comparisons:

Alignment Point 1: Calculate the leg penetration and foundation spring stiffnesses for the two interpreted soils conditions, one sand and one clay.

Alignment Point 2: Undertake the overall system geometry checks, calculate the wind areas and leg hydrodynamic coefficients, prepare a model that complies with the requirements of the standard, calculate both a pinned natural period and one incorporating spudcan fixity and also determine sway stiffness to a ‘unit’ loading applied to the hull.

Alignment Point 3: Determine loading directions, develop quasi-static wind, wave and current loads and calculate the dynamic amplification factors.

Alignment Point 4: Calculate the structural response and summarise the breakdown of loadings (wind, wave-current, inertia) and responses (hull sway, footing reactions and forces in legs at base of rack chock).

Alignment Point 5 - Final results: Assess the strengths, addressing the effects of any additional penetration, develop the chord and bracing loads and utilisation checks for the leg members, holding system and any remaining limit states set out in the standard.

2.2.4 The deliverables include a report that details the findings of the study. Some specific items that need to be brought out in the report include:

Executive Summary.

Completed Tables with inputs and outputs.

Inputs and outputs of the complicated calculations

Intermediate results and comments.

Full comments and results at Alignment Points. The report shall include quantification of any differences in results between the two consultants and the significance of those differences.

Detailed analysis of differences between SNAME and ISO.

Commentary on clauses which caused confusion or that required making assumptions.



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3 SITE SPECIFIC ASSESSMENT OF THE SUPER GORILLA

3.1 GENERAL

3.1.1 This site specific analysis aims to blaze a trail through the analysis methods recommended in the ISO document while checking that the document is complete and generates reasonable results.

3.1.2 Figure 1 shows the flowchart from Figure 5.2-1 in the ISO document. It gives the guidance for a general analysis route and provides the basic structure of this analysis.

3.1.3 The site assessment analysis is based on an exemplary LeTourneau Super Gorilla Class jack-up unit but with adjusted leg-to-hull connection stiffness values, with the results at each alignment point cross checked with those of Global Maritime. The results at each alignment point along with those of Global Maritime and the equivalent SNAME analysis have been presented in the following sections. It is noted that because the assessment has used adjusted leg-to-hull connection stiffness values, the results presented are for the purposes of benchmarking alone, and are not representative of the Super Gorilla.



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Figure 1 Flow chart for the overall assessment



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3.2 ASSESSMENT CONDITION

3.2.1 A Super Gorilla Class jack-up unit will be assessed at two specific foundation/metocean locations for the situations listed in Table 3-1.

Table 3-1 Assessment Situations of the Unit

Location Site 1 Site 2

Limit State ULS (Ultimate Limit States)

Exposure Level L1 = SI Manned Non- evacuated / C1 High Consequence

Associated criteria[1] 50-year individual extremes with action factor = 1.15

Local regulation Assume not applicable

Foundation type Sand Clay

Spudcan Reaction Point According to spudcan penetration as specified in Clause A.8.6.2

Centre of gravity CoG assumed to be located at the leg centroid

Specific Hull elevation wrt LAT 20,9m 19,7m

[1] Determined by the limit state and the exposure level.

3.3 RIG DATA

3.3.1 The rig data for this analysis is listed in Table 3-2.

Table 3-2 Assembled Rig Data

Rig Type Letourneau Super Gorilla Class

Drawings & specifications Key rig drawings held in house

Operation manual Held in house

Rack-chock[1] Kv = 634,0x103, Kh = 278,3x103

Upper-guide K = 71 430 (Gap = 3,18mm)

Lower-guide K = 89 289 (Gap = 12,70mm)

Leg-hull connection stiffness[3] (tonnes/m)

Pinion[2] K = 142 814 (Backlash = 16,0mm)

Principle Dimensions:

Hull Length x Width x Height 92,27m x 91,24m x 10,97m

Leg Length including spudcan 174,85m

Weight & Centre of gravity:

Hull lightship[4] 15 184,9 tonnes

LCG=0,0m, TCG=0,0m, VCG=11,74m

Assessed Maximum Variable Load Assessed Minimum Variable Load

4 209,1 tonnes 2 104,1 tonnes

3 Legs including spudcans[4] 7 322,4 tonnes

LCG=19,20m, TCG=0.0m

Preload (jacking reaction per leg) 13 490 tonnes



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Spudcan dimensions:

Height of spudcan 8,50m (from drawings)

Maximum bearing area 243,21 m2 (calculated from key dimensions)

Height of max bearing area above tip 1,22m

Density of steel 7.85 tonnes/m3

Relevant modifications N/A

[1] Chock stiffness per chord [2] Stiffness per pinion pair [3] Stiffnesses, guide gaps and backlashes are artificial numbers provided by the rig designer for the

purposes of this analysis [4] Centres of gravity measured from the leg centroid at the keel level, +ve fwd and to port.

3.4 SITE DATA

3.4.1 Two sites were assessed for the Super Gorilla as listed in Table 3-3.

Table 3-3 Assembled Site Data

Site 1 Site 2

Site coordinates N/A N/A

Seabed type Sand Clay

Water depth (LAT) 121,9m 85m

3.5 METOCEAN DATA

3.5.1 The metocean conditions being assessed for the two sites are based on ‘storm’ conditions detailed within the operations manual for this unit and are summarised in Table 3-4.

Table 3-4 Assembled Metocean Data[1]

Site 1 Site 2

Water depth (LAT) (m) 121,9m 85m

Data type 50-year return individual extreme

Mean high water spring tide (m) 1,22m

Storm surge (m) 1,22m

Maximum wave height (m) 26,8

Associated period (s) 16,6 (Intrinsic)

Significant wave height (m) 14,4

Peak period (s) 16,6 (Intrinsic)

Specified airgap (m) 20,9 19,74

Top Surface 1,49

25% Water Depth 1,33

Current velocity profile (m/s)




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1m above seabed 0,82

1 minute wind speed (m/s) 51.5

Other Data Marine Growth = 12.5mm

3.6 MINIMUM HULL ELEVATION CHECK

3.6.1 A hull elevation resulting in at least 1.5m clearance between the extreme wave crest and the underside of the hull shall be used. This must be checked before continuing the assessment.

3.6.2 The check which is based on the metocean data obtained previously is shown in Table 3-5

Table 3-5 Hull Elevation Check


Mean high water spring tide (m) 1,22

Storm surge (m) 1,22

Maximum wave crest height (m) 15,1 15,8

Extreme still water level (SWL) (m) = 124,4 82,4

Required margin (m) 1.50

Other allowances (m) N/A

Minimum required hull elevation (m) = 19,04 19,74

Specified hull elevation (m) = 20,90 19,74

(minimum used)

If Airgap > = Minimum, ok; otherwise, re-define Airgap

OK OK

3.7 GEOTECHNICAL AND GEOPHYSICAL DATA

3.7.1 The foundation parameters obtained for the two locations following the ISO methodology are listed in Table 3-6.

Table 3-6 Assembled Foundation Data


Soil type Sand Clay

Spudcan penetration (m) 0,9 42,0

Foundation Capacity

Vertical VLo (kN) 155 741 193 210

Horizontal HLo (kN) 18 689 53 136

Moment MLo (kN-m) 164 799 387 310

Foundation Stiffness

Vertical K1 (kN/m) 1 920 341 7 108 739



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Horizontal K2 (kN/m) 1 820 768 4 881 334

Moment K3 (kN-m/rad) 63 710 195 442 090 845

Distance of effective penetration point below sea floor (m)

0,45 37,75

3.7.2 Note, due to the differences in the geotechnical methodologies adopted by the ISO and the SNAME methodologies there may be differences in the results obtained for given spudcan and preload data.

3.8 LEG LENGTH RESERVE CHECK

3.8.1 The leg length reserve above the upper guides should reflect the uncertainty in the prediction of leg penetration and account for any settlement. The leg length reserve shall be at least 1,5 m.

3.8.2 The check based on the rig data and the metocean data obtained previously is listed in Table 3-7.

Table 3-7 Leg Length Reserve Check


Keel to top of Upper Guide (m) 26,00

Keel above sea level LAT (m) 20,9 19,74

Water depth LAT (m) 121,9 85.0

Spudan penetration (m) 0,9 42,0

Total length used (m) = 169,7 172,7

Leg length (m) 174,85

Leg length reserve (m) = 5,15 2,15

3.9 LEG AND SPUDCAN BUOYANCY

3.9.1 The leg and spudcan buoyancy at the two locations is reported in Table 3-8.

Table 3-8 Leg & Spudcan Buoyancy


Water Depth (m) 121,9 85.0

Spudcan height (m) 8,5

Single leg buoyancy (without spudcan) (tonnes) 379,8 393,4

Spudcan submerged buoyancy (tonnes) 72,6



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3.10 HYDRODYNAMIC COEFFICIENTS

3.10.1 The hydrodynamic modelling of the jack-up leg may be carried out by utilising “detailed” or “equivalent” techniques, corresponding to the levels of structural modelling.

3.10.2 In the equivalent leg model, the hydrodynamic coefficients are calculated corresponding to the equivalent diameter of each bay of the leg stick. In this analysis, the equivalent stick leg model was used to calculate the global reactions of the unit and thus the “equivalent” hydrodynamic model was used to compute the hydrodynamic coefficients.

3.10.3 The hydrodynamic properties defined for each section of the 3 legs are shown in Table 3-9 to Table 3-13. This data was calculated following the ISO methodology with the leg dimensions based on leg drawings held in house for the Super Gorilla.

Table 3-9 Hydrodynamic Surface Condition Levels

Site 1 Site 2

Water depth (m) 121,9 85,0

Mean high water spring tide (MHWS) (m) 1,22 1,22

Mean water level (MWL) (m) = 123,12 86,22

MWL + 2m = 125,12 88,22

Spudcan penetration beneath seafloor (m) 0,9 42,0

MWL above spudcan tip (m) = 124,02 128,22

Table 3-10 Hydrodynamic Leg Sections for Site 1 (sand)

Hydrodynamic Sections[1] Leg Section

Top of Section above can tip (m) Bow Leg Port Leg Stbd Leg

1 8,50 - [2] - [2] - [2]

2 42,00 (1) Lower Leg (1) Lower Leg (1) Lower Leg

3 111,81 (2) Upper Leg (2) Upper Leg (2) Upper Leg

4 126,01 (3) Bow RWS Rough (4) Port RWS Rough (2) Upper Leg

5 143,72 (5) Bow RWS Smooth (6) Port RWS Smooth (7) Upper Leg

Smooth

6 174,95 (7) Upper Leg

Smooth (7) Upper Leg


Smooth [1] Raw water structures considered were different for the bow and port legs with no raw water

structure on the stbd leg. [2] Spudcan hydrodynamic model was not considered. - No direct guidance provided in the ISO

document (Ref [2]).



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Table 3-11 Hydrodynamic Leg Sections for Site 2 (clay)

Hydrodynamic Sections Leg Section

Top of Section above can tip (m) Bow Leg Port Leg Stbd Leg

1 8,50 - - -

2 42,00 (1) Lower Leg (1) Lower Leg (1) Lower Leg

3 116,02 (2) Upper Leg (2) Upper Leg (2) Upper Leg

4 130,22 (3) Bow RWS

Rough (4) Port RWS

Rough (2) Upper Leg

5 146,74 (5) Bow RWS

Smooth (6) Port RWS


Smooth

6 174,95 (7) Upper Leg



Smooth

[1] Same methods used for Site 1 table were applied here so the notes were omitted.

Table 3-12 Member details for hydrodynamic calculations

Input - Hydrodynamic Section 1 - Lower Leg

Chord Horizontal Diagonal Internal RWS [1]

Length (m) 10,21 16,15 9,28 7,34 None

Diameter (m) 0,7490 [2] 0,4064 0,4064 0,2290 None

Angle to horizontal 90 0 30.00 0 None

Input - Hydrodynamic Section 2 - Upper Leg


Length (m) 10,21 16,15 9,28 7,34 None

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 None


Input - Hydrodynamic Section 3 - Bow RWS Rough


Length (m) 10,21 16,15 9,28 7,34 10,21

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 2 x 0.457

Angle to horizontal 90 0 30.00 0 90

Input - Hydrodynamic Section 4 - Port RWS Rough


Length (m) 10,21 16,15 9,28 7,34 10,21

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 1 x 0.457




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Input - Hydrodynamic Section 5 - Bow RWS Smooth


Length (m) 10,21 16,15 9,28 7,34 10,21

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 2 x 0.457


Input - Hydrodynamic Section 6 - Port RWS Smooth


Length (m) 10,21 16,15 9,28 7,34 10,21

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 1 x 0.457


Input - Hydrodynamic Section 7 - Upper Leg Smooth


Length (m) 10,21 16,15 9,28 7,34 None

Diameter (m) 0,7490 [2] 0,3556 0,3556 0,2290 None


[1] Raw water structures considered were different for the bow and port legs with no raw water structure on the stbd leg.

[2] The chord is formed of a split tube of diameter = 0,558m and a rectangular rack of length = 0,5856m from tooth root to tooth root. Chord width (tooth root to opposite tip) is 0,792 m and chord depth 0,749 m

Table 3-13 Base Hydrodynamic Coefficients for Tubulars

Surface condition CDi CMi

Smooth (Above MWL + 2m) 0.65 2.0

Rough (Below MWL + 2m) 1.00 1.8

3.10.4 There is no site specific information on marine growth thickness and so a thickness of 12.5mm was applied to all leg members below MWL + 2m.



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3.10.5 The chord hydrodynamics are covered in the following section, Figure 2 shows the chord section axes system.

Figure 2: Chord section axes system

3.10.6 Based on A.7.3-7 and A.7.3-8 the chord member drag and inertia coefficients are

calculated as follows:

Table 3-14 Chord hydrodynamic coefficients

Angle Smooth

(above MWL+2m) Rough

(below MSL+2m)

() CD CM De CD CM De

0 0,650 2,0 1,000 1,8

15 0,650 2,0 1,000 1,8

30 0,712 2,0 1,042 1,8

45 1,005 2,0 1,238 1,8

60 1,416 2,0 1,515 1,8

75 1,767 2,0 1,750 1,8

90 1,903 2,0 1,842 1,8

105 1,767 2,0 1,750 1,8

120 1,416 2,0 1,515 1,8

135 1,005 2,0 1,238 1,8

150 0,712 2,0 1,042 1,8

165 0,650 2,0 1,000 1,8

180 0,650 2,0

0,749

1,000 1,8

0,774

3.10.7 Rough values include the effect of marine growth, smooth values do not. Note CM does not change for marine growth.

3.10.8 The equivalent hydrodynamic coefficients for all leg sections and all flow directions were calculated using the methods defined in Clause A.7.3.2 of the ISO document (Ref [2]). A summary of the hydrodynamic coefficients at 0 , 30o, 45o and 90º flow directions (anti-clockwise, with 0 being flow onto the bow) is listed in Table 3-15



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Table 3-15 Equivalent Hydrodynamic Coefficients for Stick Leg Model

Hydrodynamic Section

Flow direction CD.De (m) CM.D2 (m2) Added mass per unit length (t/m)

0 4,409

30 4,558

45 4,495 1 - Rough

60 4,409

8,070 2,593

0 6,203

30 6,337

45 6,276 2 - Rough

60 6,203

7,121 2,349

0 7,167

30 7,301

45 7,241 3 - Rough

60 7,167

7,958 2,684

0 6,685

30 6,819

45 6,759 4 - Rough

60 6,685

7,540 2,499

0 5,004

30 5,152

45 5,086 5 - Smooth

60 5,004

7,513 -

0 4,706

30 4,855

45 4,792 6 - Smooth

60 4,706

7,095 -

0 4,409

30 4,558

45 4,495 7 - Smooth

60 4,409

6,677 -



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4 ALIGNMENT POINTS AND COMMENTS

4.1 GENERAL

4.1.1 The analysis using the ISO recommended approaches has been divided into 5 steps and at each step, the results were cross-checked with the co-workers from the ISO committee. These are called Alignment Points and are presented in this section.

4.1.2 All data presented as submission for alignment is duplicated in the following sections with comments on any differences at each alignment point.

4.2 ALIGNMENT POINT 1 - GEOTECHNICAL CALCULATIONS

4.2.1 A comparison of the initial geotechnical inputs and outputs between GLND and RPS (on behalf of Global Maritime) for the Sand and Clay assessment cases are presented in Table 4-1 and Table 4-2.

4.2.2 Comments to the differences between GLND and RPS, and ambiguities arising from ISO are bulleted after each table for the Sand and Clay cases respectively

Table 4-1 Summary of Site 1 (sand) assessment key inputs and outputs from analyses

Analysis GLND GM / RPS units

15 876 15 876 tonnes

155,7 155,7 MN Preload footing reaction, VL

35 000 35 000 kips

8 473 8 901 tonnes

83,1 87,3 MN Stillwater footing reaction, VSW

18 680 19 623 kips

Spudcan area, A 156,3 156,2 m2

Spudcan volume, V 1 165 1 177 m3

Rig Physical attributes

Tip to max. area length 1,22 1,20 m

Backflow density - - kN/m3 Angle of shearing resistance used 29 29 degrees

Hcav - - m

Penetration calculation

Tip penetration depth 0,9 0,9 m

Laterally projected area, As 7,7 99,4 m2

Su at max area, Suo - - kPa

Su at spudcan tip (Su,l) - - kPa Interface friction angle, � 29 29 degrees

Utilisation origin 0,5QV/�R,VH 7 216 tonnes

Qvnet - - tonnes a - - - b - - -

V-H Envelope Calculation

CHdeep - - -

15 876 15 876 tonnes QV

155,7 155,7 MN

Foundation yield surface definition

QH 1 905 1 905 tonnes



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18,7 18,7 MN

16 799 tonne-m QM

164,8 164,7 MNm Fixity 'n' parameter 0,0 - - Yield Surface 'alpha' parameter - - -

Su used to determine G - - kPa Relative Density 60 60 % G 54 444 55 829 kPa OCR - - - Poisson ratio, v 0,2 0,2 -

Kd1 1,00 - -

Kd2 1,00 - -

Kd3 1,00 - -

195 753 200 612 tonnes/m K1

1 920 1 968 MN/m

185 603 190 214 tonnes/m K2

1 821 1 866 MN/m

6 494 413 6 650 255 t-m/rad

Spudcan fixities

K3 63 710 65 239 MNm/rad

Initial comments arising from comparison with RPS’s values

Site 1 (sand) assessment

The geotechnical outputs are generally in good general agreement with those of RPS;

RPS’s stillwater footing reaction for the Super Gorilla is 426t greater than ND’s. We believe this to be entirely due to our stillwater footing reactions including all water buoyancy for the assumed water depth;

We have checked and were we to have used the same stillwater footing reaction as RPS, we would have predicted virtually identical fixities to those calculated by RPS. The difference in fixities is therefore due to the above discrepancy in the stillwater footing reactions used by GLND and RPS;

RPS have not reported the laterally projected area, As, and interface friction angle, , that will be used for the sliding check;

Although a ‘n’ value of -0.5 is specified in the RFQ for the deep penetration case, no value has been specified for the shallow penetration case, therefore we intend to use a value of 0,0.

There was close agreement with the foundation parameters and it was agreed to use GLND’s values going forward.



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Table 4-2 Summary of Site 2 (clay) foundation key inputs and outputs from analyses

Analysis GLND GM / RPS units 15 876 15 876 tonnes 155,7 155,7 MN Preload footing reaction, VL

35 000 35 000 kips 8 582 8 901 tonnes 84,2 87,3 MN

Stillwater footing reaction, VSW

18 920 19 623 kips Spudcan area, A 243,2 243,3 m2 Spudcan volume, V 1 165 1 177 m3

Rig Physical attributes

Tip to max. area length 1,22 1,20 m

Backflow density same as in-situ profile kN/m3

Angle of shearing resistance used - - degrees

Hcav 5,1 m

Penetration calculation

Tip penetration depth 42,0 42,5 m

Laterally projected area, As 99,4 - m2

Su at max area, Suo 59 - kPa

Su at spudcan tip (Su,l) 61 - kPa Interface friction angle, - - degrees Utilisation origin 0,5QV/R,VH 8 563 tonnes

Qvnet 14 672 tonnes a 0,93 - b 0,28 -

V-H Envelope Calculation

CHdeep 0,37 - 19 695 15 876 tonnes

QV 193,2 155,7 MN 5 416 5 450 tonnes

QH 53,1 53,5 MN

39 481 tonne-m QM

387,3 379,3 MNm Fixity 'n' parameter -0,5 -

Foundation yield surface definition

Yield Surface 'alpha' parameter 1 -

Su used to determine G 64 - kPa Relative Density - - % G 50 497 62 800 kPa OCR 1,1 1,1 - Poisson ratio, v 0,5 0,5 -

Kd1 2,00 2,10 -

Kd2 2,06 2,11 -

Spudcan fixities

Kd3 2,41 2,44 -



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724 642 948 624 tonnes/m K1

7 109 9 306 MN/m 497 588 633 639 tonnes/m

K2 4 881 6 216 MN/m

45 065 326 56 886 137 t-m/rad

Spudcan fixities (continued)

K3 442 091 558 053 MNm/rad

Initial comments arising from comparison with RPS’s values

Site 2 (clay) assessment

Input parameters

RPS’s stillwater footing reaction for the Super Gorilla is 426t greater than GLND’s. We believe this to be entirely due to our stillwater footing reactions including all water buoyancy for the assumed water depth;

We have linearly interpolated Su and G with respect to depth as instructed; OCR and ’ have been assumed to be constant within each soil unit

(consistent with RPS); We used the same laterally projected area for Super Gorilla as RPS.

Penetration Calculation

We have used the average backflow unit weight for the backflow soil to calculate the backflow weight on top of the spudcan;

The Houlsby & Martin approach is not applicable in this instance as the value for Sum leads to a B/Sum ratio of 9,62 which is outside the range of applicability.

It is not clear how you would use Houlsby & Martin’s parameters in layered soils, should Sum be the Su at the top of each layer or at the seabed surface?;

It is noted in Edwards et al. (Géotechnique 2005 No. 55, No. 10) showed that Houlsby & Martin’s values are notably lower (i.e. less accurate) than the upper and lower bound solutions derived by Martin and FE data;

No guidance is provided on how to average undrained shear strength with depth if a sand layer is encountered;

No guidance is provided in ISO on how to assess infill. In this case no sand is present at the seabed surface so we have assumed no infill occurs;

GLND has used Skempton’s bearing capacity and depth factors with an averaged Su;

We recognise that our load-penetration curve does not incorporate a detailed analysis of the initiation of backflow, and the corresponding spudcan buoyancy within the transition to full backflow, however the penetration resistance profile for penetrations greater than those required for full immersion of the spudcan in the soil is correct;

We note that the predicted spudcan penetration depths will limit the water depth that can be used in the subsequent engineering assessment stage of the benchmarking exercise.



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V-H Capacities

The choice of whether to use an averaged Su or modified bearing capacity factor in the spudcan penetration calculations will lead to different ‘b’ values for horizontal capacity. With reference to the case of a flat circular footing at the surface we propose that the Su in the ‘b’ equation should be Su at the depth of the max. plan area (i.e. Suo);

The stillwater footing reaction presented in the FV-FH plot includes all water buoyancy, backflow weight and spudcan ‘soil buoyancy’;

RPS appear to have taken QV as the preload footing reaction (VLo) but this is incorrect (as per Eq. A.9.3-1b and A.9.3-3).

Fixities

RPS have reported they have used a Poisson’s ratio of 0.2 - it should be 0.5 in clay, we presume this is just a typographic error;

We cannot match RPS’s values for spudcan stiffnesses which are greater than ours;

It is unclear what G value should be used for the present benchmarking assessment; we have used an interpolated G value based on the values provided in the table. It is noted that this is significantly greater than 400Su (using Su at D+0.15B as per guidelines);

The guidance in the ISO document is unclear on what IrNC should actually be used, when should the data in Fig A.9.3-12 actually be used?

The symbol for over-consolidation ratio in Equation A.9.3-36 is still ‘O’ instead of ROC;

Although ‘n’=-0.5 is specified for the fixity degradation relationship in the RFQ, software modifications have yet to provide a stable solution with ‘n’=-0.5. ‘n’=0,0 has been used instead. We note this is likely to result in slightly lower moment fixity for legs with low RFs which is conservative;

We have used the depth factors given in Table A.9.3-4 but note that these are the same as those given in SNAME (2008) for a Poisson’s ratio of 0,0 (not appropriate for soil!), not 0,5, as it should be for clay;

The unit weight for backflow, for use with any additional penetrations, has been taken as that at the depth of max. plan area;

We have recommended an adhesion factor, , of 1.0 due to the penetration depth and strength of the soil at that depth (not specified by RPS);

We have not used P-Y curves to supplement the spudcan fixities; For the predicted penetration depth, 2D/B>4, consequently we have used the

fixity depth factors for 2D/B=4.

4.2.3 From the above it is evident that the majority of differences between foundation assessment values arose from interpretation of the design soil profile rather than interpretation of ISO or differences in assessment technique.

4.2.4 After revision of the input parameters after discussions between parties there was close agreement with the foundation parameters and it was agreed to use GLND’s values going forward.



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4.3 ALIGNMENT POINT 2 - OVERALL SYSTEM CHECKS

4.3.1 At this point, the following calculations were submitted for alignment:

Overall system geometry checks (leg length reserve);

Wind area and leg hydrodynamic coefficients;

Natural periods (pinned, with 80% fixity and 100% fixity, with or without P-Delta effect);

Hull sagging.

In addition to these a model was prepared which complied with the requirements of the standard, where possible based on an existing model of the unit.

4.3.2 The leg length reserve check submitted is listed in Table 4-3.

Table 4-3 Leg Length Reserve Check

Location Site 1 (sand) Site 2 (clay)

Keel to top of Upper Guide (m) 26,0

Keel above sea level LAT (m) 20,9 19,7

Water depth LAT (m) 121,9 85,0

Spudan penetration (m) 0,9 42,0

Total length used (m) = 169,7 172,7

Leg length (m) 174,9

Leg length reserve (m) = 5,2 2,2

4.3.3 The wind area calculations are listed in Table 4-4. The 60 , 90º and 120º flow directions (anti-clockwise, with 0 being flow onto the bow) have been identified as the controlling cases in this analysis and thus only the calculation results for these directions are listed for comparison.

Table 4-4 Wind Area Calculations (m2)

Storm heading [1] Exc Shape Coefficient Inc. Shape Coefficient

60˚ 3 664,3 4 778,6

90˚ 3 521,2 4 590,7

120˚ 3 039,6 3 985,2 [1] Anti-clockwise, with 0,0˚ being flow onto the bow

4.3.4 GM confirmed by email (Bing Deng’s email of 16th April 2010) that their model had near-identical windage values (although no specific values provided), the values presented above are therefore taken as being aligned.



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4.3.5 The equivalent hydrodynamic coefficients for the stick-leg models at the two sites, following the ISO specifications, are listed in Table 4-5.

Table 4-5 Equivalent Hydrodynamic Coefficients for Stick Leg Model

GLND GM Top of Section above can tip (m)

Flow direction CD.De (m)

CM.D2 (m2)

CD.De (m) CM.D2 (m2)

% Difference

0, 60, 120 6,594 6,284 Up to 42m

30, 60, 90 6,735 8,070

6,413 7,558 5

0, 60, 120 6,203 5,945 42m to MSL+2m (no raw water tower) 30, 60, 90 6,337

7,121 6,074

6,785 4

0, 60, 120 7,167 6,914 42m to MSL+2m (bow leg raw water tower) 30, 60, 90 7,301

7,958 7,043

7,568 4

0, 60, 120 6,685 6,429 42m to MSL+2m (port leg raw water tower) 30, 60, 90 6,819

7,540 6,559

7,307 4

0, 60, 120 4,409 4,555[1] Above MSL+2m (no raw water tower) 30, 60, 90 4,558

6,677 4,701[1] 6,524[1] -3

0, 60, 120 5,004 - Above MSL+2m (bow leg raw water tower) 30, 60, 90 5,152

7,513 -

- -

0, 60, 120 4,706 - Above MSL+2m (port leg raw water tower) 30, 60, 90 4,855

7,095 -

- -

[1] Single value for leg above MSL+2m given

4.3.6 GLND’s drag coefficients calculated based on chord member geometry according to ISO formulae were up to 5% greater than Global Maritime’s values, which were stated to be in agreement to the designer benchmarked values.

4.3.7 For the purpose of this assessment, and transparency in the “go-by” calculation pack it was agreed to proceed with GLND’s values.

4.3.8 The unit was modelled using the equivalent 3-leg stick model (see Figure 3) for global loading, in conjunction with the single detailed leg model (see Figure 4) for leg and holding system strength checks. The modelling methodology is described below:

The leg properties of the 3-leg model were calibrated against the characteristics of the detailed single leg model for a consistent approach;

The hull represented in the equivalent leg model is constructed of stiff beams representing the approximate stiffness of the actual hull;

The leg to hull connection is modelled in the equivalent leg model using an equivalent spring with calculated vertical and rotational stiffness’s. The detailed leg model leg to hull connection is represented by a series of springs



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and gaps arranged such that they represent the upper and lower guides, pinions and chocks.

Figure 3: 3 Stick Leg Model (showing hull beam grillage)

(leg below hull cropped for reporting purposes)

Figure 4: F.E. Model of Hull/Leg Interface

Jackframe

Upper Guide

Pinions

Chocks

Jack-posts

Lower Guide

Leg

chor

d

Leg

chor

d

chor

dLe

g



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4.3.9 The mass of the equivalent 3 leg model has been represented by adjusting the density of each element in the leg and the hull to produce the correct mass distribution over the whole unit. Different masses were used for different parts of the analysis, for example leg added mass was incorporated into the dynamic analysis model but was removed for the quasi-static analysis. It should be noted that most of the analyses were performed with gravity turned off in which case vertical forces are added to the model to represent the vertical effect of the mass distribution.

4.3.10 The mass of the detailed leg model was modelled by applying small vertical forces to each node in the model along the whole length of the leg instead of using either discrete or distributed masses as in this case gravity is turned off.

4.3.11 Leg inclination was incorporated into the detailed leg model by applying a series of vertical couples up the leg which summed to give the total leg inclination moment. The leg inclination moment was calculated assuming an offset of 0.5% of the leg length below the hull as stipulated in A.10.5.4.

4.3.12 The natural periods calculated using the in-house software FORCE-3 are listed in Table 4-6.

Table 4-6 Natural Periods (Max hull weight = 19 394 tonnes)

Mode

Linear frequency

(Hz)

Linear period (s)

Nonlinear frequency

(Hz)

Nonlinear period (s)

Sway 0,1034 9,67 0,0930 10,75 Pinned

Yaw 0,1295 7,72 - -

Sway 0,1275 7,84 0,1243 8,04 80% Rotational

Fixity Yaw 0,1526 6,55 - -

Sway 0,1337 7,48 0,1286 7,78

Site 1 (sand)

100% Rotational

Fixity Yaw 0,1596 6,26 - -

Sway 0,1043 9,59 0,0971 10,30 Pinned

Yaw 0,1306 7,66 - -

Sway 0,1657 6,04 0,1618 6,18 80% Rotational

Fixity Yaw 0,1895 5,28 - -

Sway 0,1682 5,94 0,1647 6,07

Site 2 (clay)

100% Rotational

Fixity Yaw 0,1921 5,21 - -

4.3.13 Global Maritime’s natural period for the sand assessment condition was reported to be 10,0 seconds for the ‘pinned’ assessment case and 7,6-8,2 seconds (SACS calculation vs formula) for inclusion of linearised fixity in reasonable agreement with GLND’s values.

4.3.14 It is expected that differences in the leg-to-hull connection stiffness is the cause of the above differences. No further investigation of this has been completed but should be borne in mind for the final results.



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4.3.15 The sway stiffness has been analysed with a unit loading of 19,62MN (2,000 tonnes) applied at the hull centre of gravity (CoG) for cases with and without p-delta loading. Results are summarised in Table 4-7.

Table 4-7 Hull Displacements and Sway Stiffness

Displacements (m) Sway stiffness (MN/m) Foundation conditions Excluding

P-Delta effects Including

P-Delta effects Excluding

P-Delta effects Including

P-Delta effects

Site 1 (sand)

Pinned 2,05 2,41 9,552 8,144

Linear Fixity: 80% K3 (rot) 100% K3 (rot)

1,32 1,24

1,43 1,34

14,864 15,784

13,711 14,653

Fixed 0,69 0,72 28,271 27,441

Site 2 (clay)

Pinned 2,08 2,34 9,675 8,385

Linear Fixity: 80% K3 (rot) 100% K3 (rot)

0,82 0,80

0,86 0,83

23,840 24,556

22,841 23,553

Fixed 0,69 0,71 28,601 27,595

4.3.16 No comparable data was received from Global Maritime.

4.3.17 Reactions are reported for a gravity loadcase with ‘pinned’ foundation restraint condition accounting for 25% hull sag. Footing reactions are reported in Table 4-8

Table 4-8 Footing reactions from gravity loadcase

Leg F-X (kN) F-Y (kN) F-Z (kN)

Bow -122,6 0,0 83 381

Port 61,3 -110,8 83 150

Stbd 61,3 110,8 82 908 Site 1 (sand)

Total 0,0 0,0 249 439

Bow -123,6 0,0 83 228

Port 61,8 -111,5 83 007

Stbd 61,8 111,5 82 775 Site 2 (clay)

Total 0.0 0,0 249 010

4.3.18 The difference in vertical reaction of approximately 429kN is due to additional leg buoyancy in the clay case attributed to a slightly greater penetration and waterdepth combination.

4.3.19 No comparable data was received from Global Maritime.

4.3.20 The complete data pack above was submitted to Global Maritime for alignment and general agreement to proceed with the GLND values was received from Alberto Morandi by email of 29th July 2010.



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4.4 ALIGNMENT POINT 3 - ENVIRONMENTAL LOADINGS

4.4.1 At this point, the following calculations were submitted for alignment:

Loading direction for analysis;

Quasi-static wind, wave and current loads;

Dynamic amplification factors (DAFs).

4.4.2 The worst case loading directions for, preload and foundation bearing capacity, leg and holding system strength and overturning capacity have been defined as 60, 90 and 120 degrees anticlockwise from the bow respectively for this assessment:

+ve

0o

Storm Direction

4.4.3 Wind loads calculated by spreadsheet methods for a windspeed of 51,47m/s, inclusive of a load factor of 1.15 are presented in Table 4-9. Moment arms for different parts of the unit are presented with reference to the effective penetration.

Table 4-9 Wind Loads

Force / Arm

Storm Direction Leg Below Hull Hull Leg Above Hull

060˚ 133,0kN / 140,25m 8 868kN / 162,62m 147,0kN / 171,85m

090˚ 132,2kN / 140,59m 8 529kN / 162,64m 147,0kN / 171,85m Site 1 (sand)

120˚ 136,8kN / 140,67m 7 383kN / 163,74m 147,0kN / 171,85m

060˚ 96,9kN / 139,19m 8808,8kN / 161.61m 59,7kN / 169,31m

090˚ 96,7kN / 139,97m 8471,7kN / 161,63m 59,7kN / 169,31m Site 2 (clay)

120˚ 98,3kN / 139,60m 7333,7kN / 162,73m 59,7kN / 169,31m

4.4.4 Note, the length of leg below the hull considered in the wind force calculations is calculated from the water surface to the keel level. The water surface elevation is different for each leg as it is calculated from the wave profile at the phase which corresponds to the maximum wave loading on the unit.

4.4.5 No comparable data was received from Global Maritime although they confirmed that the “wave / wind / current loads agree very closely (within 1%)” - Alberto Morandi’s email of 22nd August 2010.



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4.4.6 Quasi-static wave and current loads, calculated using the in-house software FORCE-3, are listed in Table 4-10. A load factor of 1.15 has been applied. Wave and current Loads are presented in Table 4-10 are based on the leg sections and raw water structure previously detailed based on the following wave and current input parameters:

Significant wave height Hsrp = 14,4m

Peak wave period Tp = 16,6s

Current: Surface Vc surface = 1,49m/s [1]

Seabed Vc seabed = 0,81m/s [1]

Table 4-10 Wave / Current Loads (LF=1,15)

Storm Direction Wave/Current Force

(kN) [1] Wave/Current Moment

[2] (MN.m)

060˚ 20 700 1 941,4

090˚ 21 045 1 964,6 Site 1 (sand)

120˚ 20 355 1 906,8

060˚ 21 045 2 157,7

090˚ 21 160 2 162,0 Site 2 (clay)

120˚ 20 470 2 101,6

[1] Reduction in current velocity (due to current blockage) has been omitted from the assessment - had this been included this would save approximately 10% on current loading, equivalent to approximately 5% on the overall.

[2] Moments taken from point of effective penetration (0.46m above the spudcan tip for sand, 4,25m above the spudcan tip for clay).

4.4.7 As per ISO requirements the ‘apparent’ wave period was used to determine the wave position that resulted in the peak overall loading, with the ‘intrinsic’ wave period used to determine the wave particle kinematics.

4.4.8 No comparable data was received from Global Maritime although they confirmed that the “wave / wind / current loads agree very closely (within 1%)” - Alberto Morandi’s email of 22nd August 2010.

4.4.9 Had we fully allowed for reduction in current velocity (ISO A.7.3-18) then a larger difference in results (4-5%) may be anticipated - it is not clear if current blockage has been allowed for by Global Maritime in their assessment.

4.4.10 The following table describes how each of the actions applied to the unit are modelled in the quasi-static analysis

Table 4-11 Summary of actions considered

Action Modelling Details

a) Functional actions due to fixed and variable loads

Hull

Modelled as three lump masses located at each leg to hull connection along with a distributed mass across the hull structure. As gravity is turned off for most of the analyses three vertical forces are also applied to the three leg to hull connections to model the vertical effect of the masses.



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Legs

Mass is distributed up the legs appropriately however when gravity is turned off the vertical effect is modelled by vertical forces distributed up the legs.

b) Hull sagging Moments applied at the leg to hull connections

c) Wind actions Horizontal forces applied directly to nodes in the model representing the leg below the hull, hull and leg above the hull (quasi-static analysis only).

d) Wave and current actions Applied as horizontal forces to nodes up the leg

e) Inertia actions Applied as a combination of horizontal forces and moments to the hull centre of gravity node (quasi-static analysis only)

f) Large displacement effects Accounted for the software

g) Conductor actions None

h) Other applicable actions None

4.4.11 The DAF’s presented in Table 4-12 below have been calculated for both the Sand and Clay cases. Relative velocity effects have been included in the ‘mass’ analysis with the explicit damping ratio reduced from 7% to 4% (relative velocity effects account for 3%) in accordance with ISO.

4.4.12 A short investigation has been performed to establish the required simulation length using the Winterstein/Jensen approach to acquire a stable DAF for all storm headings being considered. For each case this was performed using the same storm qualified at 3, 6 and 9hrs. Example DAF’s for the 3 simulation lengths for the 90-degree direction using a MPM range of 3hrs are presented in Table 4-12.

4.4.13 Storms were qualified as stipulated in Table A.7.3-4, whereby the statistics of the storm were shown to be within the limits specified for standard deviation, skewness, kurtosis and maximum crest elevation.

Table 4-12 DAFR from varying storm durations for 90 degree loading

Site 1 (sand) Site 2 (clay)

Storm Durations 3 hr 6 hr 9 hr 3 hr 6 hr 9 hr

BS DAFR 1,14 1,15 1,16 1,27 1,27 1,27

OTM DAFR 1,32 1,34 1,35 1,44 1,43 1,43

4.4.14 Results for the storm headings considered are presented in Table 4-13

Table 4-13 DAFR from the Dynamic MPME for 60, 90 & 120-degree loading


Storm Direction 60º 90º 120º 60º 90º 120º

BS DAFR 1,18 1,16 1,13 1,34 1,27 1,26 SAND

OTM DAFR 1,39 1,35 1,31 1,50 1,43 1,35



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4.4.15 DAF’s for headings of 15˚ and 45˚ for the sand case (only) have also been computed for a test-case condition following the guidance given in the concluding paragraph of Annex C.3.

Table 4-14 DAFR from the Dynamic MPME for 15 & 45 degree loading (SAND only)

Site 1 (sand)

Storm Direction 15 45

BS DAFR 1,14 1,18 SAND

OTM DAFR 1,32 1,39

4.4.16 GLND’s usual procedure for calculating weighted average DAF’s is to use 50% of the DAF for that heading and then add 25% from each of the DAF’s of the two adjacent headings (typically for 15-degree increments).

4.4.17 The flowing chart shows a comparison between using the weighted average of DAF’s produced for 60˚, 90˚ and 120˚ (sand case) and using the DAF’s calculated for 15˚ and 45˚ around the clock as suggested in C.3.

Unfactored DAF's

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

0

30

60

90

120

150

180

210

240

270

300

330

OTM DAFBS DAFWeighted OTM DAFWeighted BS DAF15˚ OTM DAF15˚ BS DAF45˚ OTM DAF45˚ BS DAF

Figure 5 Unfactored DAF vs storm heading

4.4.18 The chart shows a much better approximation is made by using weighted average DAF’s than mid point heading DAF’s where 45o would be conservative, and 15o non-conservative even for the limited storm loading directions being considered.



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4.4.19 Therefore we propose using the weighted average DAF approach which results in the following DAF’s.

Table 4-15 DAFR from the Dynamic MPME (Hull Weight = 19394,0t)



BS DAFR 1,17 1,15 1,14 1,30 1,28 1,26

OTM DAFR 1,37 1,35 1,33 1,46 1,43 1,40

Table 4-16 DAFR from the Dynamic MPME (Hull Weight = 17290t)



BS DAFR 1,19 1,18 1,16 1,27 1,25 1,23

OTM DAFR 1,38 1,36 1,35 1,42 1,38 1,35

4.4.20 DAFs provided by Global Maritime (based on their hydrodynamic coefficients) were 1,20 BS DAF and 1,40 OTM DAF for ‘pinned’ foundation and 1,10 BS DAF and 1,22 OTM DAF when allowing for fixity. These were based on the maximum hull weight although it is unclear if these DAFs were based on apparent wave theory.

4.4.21 Global Maritime confirmed that they would proceed using our DAF’s - Alberto Morandi’s email of 22nd August 2010.



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4.5 ALIGNMENT POINT 4 - STICK MODEL RESPONSES

4.5.1 The following calculations have been submitted for alignment:

Summarised breakdown of loadings (wind, wave-current, inertia) and responses (hull sway, footing reactions and forces in legs at base of rack chock);

Reactions at the leg-to-hull and foundation interface levels based on the structural response incorporating fixity.

4.5.2 Loadings and response are based on the finite element “stick leg” model using the FORCE-3 bolt-on to the PAFEC finite element software. The final quasi-static analysis has been incorporated with 100% foundation fixity.

4.5.3 Wind loads are presented in Table 4-17 inclusive of environmental load factor of 1.15. Overturning moments are calculated about the point of effective penetration.

Table 4-17 Wind Loads (LF=1.15)

Case Storm

Direction Leg below hull Hull Leg above hull Total

Force kN 133 8 868 147 9 148 60

Moment kN,m 18 658 1 442 213 25 256 1 486 126

Force kN 132 8 529 147 8 808 90

Moment kN,m 18 593 1 387 084 25 256 1 430 932

Force kN 137 7 383 147 7 666

Site 1 (Sand)

120 Moment kN,m 19 241 1 208 834 25 256 1 253 331

Force kN 97 8 809 60 8 966 60

Moment kN,m 13 518 1 425 823 10 117 1 449 458

Force kN 97 8 472 60 8 628 90

Moment kN,m 13 562 1 371 375 10 117 1 395 055

Force kN 98 7 334 60 7 492

Site 2 (Clay)

120 Moment kN,m 13 740 1 195 275 10 117 1 219 132

4.5.4 Wave and current loads are previously presented in Table 4-10



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4.5.5 Inertial (dynamic) loads are summarised in Table 4-18. The inertia loads were calculated as (DAFR -1,0) x Wave-Current Load (Static). The load factor of 1.15 has been included in all the loads listed below. Inertia loads have been applied at the hull centre of gravity as a force and moment combination to accurately represent the BS and OTM contributions. No inertia loads have been applied to the legs above the hull given the minimal leg length protruding above the upper guides.

Table 4-18 Inertia Loads (LF=1.15)

Maximum hull weight Minimum hull weight

Case Storm DirectionForce (kN)

Moment

（kN-m） Force (kN)

Moment

（kN-m）

60 3519 718 325 3 933 737 739

90 3 157 687 601 3 788 707 247 Site 1 (Sand)

120 2 850 629 231 3 257 667 367

60 6 314 994 956 5 756 905 194

90 5 925 931 935 5 311 832 239 Site 2 (Clay)

120 5 322 842 697 4 677 736 307

4.5.6 The total loading condition is summarised in Table 4-19 (not including P-Delta loads)

Table 4-19 Total Loading (LF=1.15)

Maximum hull weight Minimum hull weight

Case Storm DirectionForce (MN)

Moment

（MN-m） Force (MN)

Moment

（MN-m）

60 33 367 4145,9 33 781 4165,3

90 33,010 4083,1 33 641 4102,8 Site 1 (Sand)

120 30,871 3789,4 31 278 3827,5

60 36,324 4607,4 35 766 4517,6

90 35,713 4494,3 35 099 4394,6 Site 2 (Clay)

120 33,284 4168,6 32 639 4062,2

4.5.7 The breakdowns of the model responses (hull sway, footing reactions and forces in legs at base of rack chock) are listed in Table 4-20 through Table 4-23.

Table 4-20 Hull Sways (m)

Location Maximum hull weight Minimum hull weight

Storm Heading Site 1 (Sand) Site 2 (Clay) Site 1 (Sand) Site 2 (Clay)

60 3,34 3,04 3,39 2,93

90 3,30 2,99 3,33 2,70

120 2,93 2,52 2,90 2,36



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Table 4-21 Footing Reactions

Maximum Hull Weight Minimum Hull Weight Site

Storm Heading

Leg Fh (kN) Fv (kN) M (kN-m) Fh (kN) Fv (kN) M (kN-m)

Bow 12 038 41 290 80 011 12 123 34 380 50 202

Port 11 946 41 980 83 436 12 041 34 980 55 070 60

Starboard 9 392 164 500 1 241 9 631 158 000 1 103

Bow 11 621 82 230 140 504 11 801 75 490 132 604

Port 11 841 12 650 7 039 12 081 6 340 8 286 90

Starboard 9 544 152 900 10 430 9 746 145 500 11 170

Bow 10 141 118 500 127 643 10 332 111 200 145 980

Port 10 785 10 450 1 543 10 806 4 750 1 703

Site 1 (sand)

120

Starboard 10 004 118 800 128 478 10 196 111 400 147 159

Bow 13 689 43 610 385 118 13 477 38 350 388 102

Port 13 586 44 420 385 447 13 381 39 050 388 629 60

Starboard 9 007 161 300 1 203 8 870 151 200 820

Bow 12 801 82 730 365 612 12 311 75 850 377 007

Port 13 815 17 260 385 369 12 888 16 670 391 380 90

Starboard 9 115 149 300 29 761 9 943 136 100 190 177

Bow 10 665 115 300 288 225 10 572 106 300 316 192

Port 12 119 18 320 390 108 11 637 15 740 390 299

Site 2 (clay)

120

Starboard 10 503 115 600 287 994 10 432 106 500 319 717



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Table 4-22 Reactions in leg below chock (SAND)

Site: SAND Storm

Heading Leg Fh (kN) Fv (kN) M (kN-m)[1]

Inclination Moment (kN-m)

Bow 4 189 23 900 1 430 308 32 158

Port 4 334 24 830 1 421 651 32 695 60

Starboard 4 047 147 600 1 605 733 128 117

Bow 3 280 64 840 1 405 127 64 043

Port 5 371 -4 504 1 454 744 9 852 90

Starboard 3 268 135 900 1 533 634 119 082

Bow 2 632 101 100 1 300 445 92 291

Port 4 933 -6 698 1 317 985 8 139

Hull Weight = 19394,0t

120

Starboard 2 929 101 900 1 290 435 92 524

Bow 4 270 16 990 1 451 137 26 776

Port 4 429 17 830 1 443 638 27 243 60

Starboard 4 286 141 100 1 628 448 123 054

Bow 3 465 58 100 1 422 096 58 793

Port 5 617 -10 810 1 471 831 4 938 90

Starboard 3 468 128 600 1 544 649 113 319

Bow 2 816 93 770 1 287 317 86 605

Port 4 953 -12 400 1 304 350 3 699

Hull Weight = 17290t

120

Starboard 3 115 94 520 1 277 091 86 761

[1] The additional leg moment due to leg inclination resulting from leg-hull clearances and hull inclination is included in the values in this column.



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Table 4-23 Reactions in leg below chock (CLAY)

Site: CLAY Storm

Heading Leg Fh (kN) Fv (kN) M (kN-m)[1]

Inclination Moment (kN-m)

Bow 5 405 25 520 1 419 498 33 796

Port 5 576 26 570 1 413 447 34 423 60

Starboard 4 232 143 700 1 562 233 124 999

Bow 3 939 64 640 1 386 137 64 112

Port 7 645 -585 1 449 050 13 376 90

Starboard 3 011 131 700 1 469 245 115 700

Bow 2 276 97 250 1 195 981 89 352

Port 7 905 467 1 275 212 14 197

Hull Weight = 19394,0t

120

Starboard 2 669 98 030 1 184 993 89 584

Bow 5 193 20 260 1 364 854 29 719

Port 5 367 21 200 1 358 723 30 262 60

Starboard 4 095 133 600 1 497 335 117 172

Bow 3 450 57 760 1 263 110 58 780

Port 6 731 -1 184 1 297 129 12 918 90

Starboard 3 843 118 500 1 336 518 105 471

Bow 2 177 88 230 1 116 506 82 377

Port 7 421 -2 112 1 193 290 12 198


120

Starboard 2 593 88 920 1 105 029 82 532

[1] The additional leg moment due to leg inclination resulting from leg-hull clearances and hull inclination is included in the values in this column.

4.5.8 Although Global Maritime confirmed that the “wave / wind / current loads agree very closely (within 1%)” - Alberto Morandi’s email of 22nd August 2010, no comparable information (based on updated hydrodynamic coefficients and ND DAFs) has been received for Alignment Point 4. The final assessment checks have been completed based on the reactions reported above.



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4.6 ALIGNMENT POINT 5 - FINAL ASSESSMENT RESULTS

4.6.1 The foundation integrity check results are presented below in Table 4-24.

Table 4-24 Footing Reactions from the Global Responses (Site: SAND; Units: MN)

SAND Storm

Direction Leg Axial Shear

Preload UC

Bearing UC

Sliding UC

Bow 41,3 12,0 0,29 0,91 0,81

Port 42,0 11,9 0,30 0,92 0,79 60˚

Stbd 164,5 9,4 1,16 1,63 -

Bow 82,2 11,6 0,58 0,72 -

Port 12,7 11,8 0,09 - 1,19 90˚

Stbd 152,9 9,5 1,08 1,47 -

Bow 118,5 10,1 0,84 1,03 -

Port 10,5 10,8 0,07 - 1,20


120˚

Stbd 118,8 10,0 0,84 1,04 -

Bow 34,4 12,1 0,24 0,99 0,92

Port 35,0 12,0 0,25 0,98 0,90 60˚

Stbd 158,0 9,6 1,12 1,54 -

Bow 75,5 11,8 0,53 0,70 -

Port 6,3 12,1 0,04 - 0,80 90˚

Stbd 145,5 9,7 1,03 1,37 -

Bow 111,2 10,3 0,79 1,06 -

Port 4,8 10,8 0,03 - 0,79


120˚

Stbd 111,4 10,2 0,79 1,06 -



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Table 4-25 Footing Reactions from the Global Responses (Site: CLAY; Units: MN)

CLAY Storm

Direction Leg Axial Shear

Preload UC

Bearing UC

Sliding UC

Bow 87,9 13,7 0,48 - 0,40

Port 88,7 13,6 0,49 - 0,40 60˚

Stbd 205,6 9,0 1,13 1,45 0,26

Bow 127,0 12,8 0,70 0,59 0,38

Port 61,6 13,8 0,34 - 0,41 90˚

Stbd 193,6 9,1 1,06 1,31 0,27

Bow 159,6 10,7 0,88 0,92 0,31

Port 62,6 12,1 0,34 - 0,36


120˚

Stbd 159,9 10,5 0,88 0,94 0,31

Bow 82,7 13,5 0,45 - 0,40

Port 83,4 13,4 0,46 - 0,39 60˚

Stbd 195,5 8,9 1,07 1,36 0,26

Bow 120,2 12,3 0,66 - 0,36

Port 61,0 12,9 0,34 - 0,38 90˚

Stbd 180,4 9,9 0,99 1,17 0,29

Bow 150,6 10,6 0,83 0,81 0,31

Port 60,1 11,6 0,33 - 0,34


120˚

Stbd 150,8 10,4 0,83 0,81 0,31

4.6.2 The utilisation checks for the most critically loaded (port and stbd) legs for the 90 degree heading (deemed worst from structural utilisations) are presented in Table 4-26 below.

Table 4-26 Member Checks (Hull weight = 19394t)

Site Leg

Member Axial (MN)

Y-Bending (MN-m)

Z-Bending (MN-m)

Y-Shear (MN)

Z-Shear (MN)

Max Section Torque (MN-m)

Combined

Utilisation

Chord -86,75 -2,830 0,278 -0,112 -0,805 -0,008 0,65

H Brace -0,68 -0,040 -0,005 -0,001 -0,007 0,001 0,09

Po r t

D Brace -4,69 -0,092 0,010 0,002 0,012 -0,002 0,52

Chord -138,01 -2,670 0,296 -0,129 -0,409 -0,008 0,99

H Brace -0,532 -0,015 0,001 0,000 0,004 0,001 0,06

SAND

S t bd

D Brace -3,74 -0.088 0,013 0,003 0,014 0,000 0,43

CLAY P Chord -86,90 -3,240 0,279 -0,111 -1,089 -0,010 0,66



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H Brace -0,92 -0,052 -0,006 -0,001 0,009 0,001 0,12 o r t

D Brace -5,75 -0,110 0,012 0,002 0,014 -0,003 0,64

Chord -133,0 -2,450 0,291 -0,127 -0,339 -0,008 0,96

H Brace 0,84 -0,004 0,000 0,000 0,000 -0,001 0,06

S t bd

D Brace -3,84 -0,089 0,013 0,003 0,013 -0,001 0,44

4.6.3 A summary of the member lengths and effective length factors used in determining the structural utilisations is provided below:

Chords: Member Length = 5,11m KY = 1,00 KZ = 1,00 Horizontal Braces: Member Length = 7,78m KY = 0,90 KZ = 0,90 Diagonal Braces: Member Length = 8,45m KY = 0,90 KZ = 0,90

4.6.4 The critical holding system utilisation checks are summarised in Table 4-27 and Table 4-28 for the port and starboard legs for the 120 degree heading.

Table 4-27 Maximum Utilisations of the Chocks

Site Leg Load (MN) Allowable Load (MN) Utilisation

Port 60,3 91,8 0,66 Sand

Stbd 78,9 91,8 0,86

Port 59,5 91,8 0,64 Clay

Stbd 75,7 91,8 0,83

Table 4-28 Maximum Utilisations of the Pinions

Site Leg Load (MN) Allowable Load (MN) Utilisation

Port 10,5 24,8 0,42 Sand

Stbd 16,2 24,8 0,65

Port 10,5 24,8 0,42 Clay

Stbd 15,6 24,8 0,63

4.6.5 The leg to spudcan connection strength has not been assessed for these assessments.

4.6.6 A summary of the final assessment result is presented in Table 4-29.



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Table 4-29 Final assessment results

Criteria Site 1 (sand) Site 2 (clay)

Hull Elevation (m) Airgap = 20,9 >

Minimum clearance = 19,04

Airgap = 19,74 >

Minimum clearance = 19,74

Leg length reserve (m)

5,2 2,2

Spudcan penetration (m)

0,9 42,0

Utilisations Heading UC Heading UC

Preload Capacity 60 1,16 60 1,13

Foundation bearing capacity

60 1,63 60 1,45

Additional settlements (m)

- 0,1 - 7,2

Windward leg sliding 120 1,30 120 0,41

Maximum Hull sway (m)

60 3,39 60 3,04

Leg chord strength 90 0,99 90 0,96

Leg brace strength 90 0,52 90 0,64

Pinion holding strength

90 0,65 90 0,63

Chock holding strength

90 0,86 90 0,83

Max Overturning 120 0,98 120 0,87

Note: The results presented above are based on adjusted leg-to-hull connection stiffness values for the purposes of benchmarking alone, and are therefore not representative of the Super Gorilla.

4.6.7 Following comments received from Global Maritime the overturning checks have been recalculated such that the P-Delta overturning contribution is accounted for only in the overturning moment. The hull sway is not used to reduce the righting moment lever arm as this would account for the P-Delta moment twice.

4.6.8 Following comments received from Global Maritime the chock and pinion utilisations have been recalculated based on a representative model of the two systems working simultaneously. The previous utilisations were based on the assumption that the pinions only take the deadweight of the unit which was an omission on GLND’s part.

4.6.9 Following a review of our analyses the chord utilisations have been recalculated. The previous utilisations were calculated assuming B ≥ 1,0 and using the equations for all strengths of steel in A.12.6.2.4, the revised utilisations use calculated B



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values and the equations for high strength steels. This has the effect of reducing the utilisations by approximately 23% for sand and 19% for clay.

4.6.10 The above results have been shared with Global Maritime. Although comments to the final results have been received, we have not seen comparable data-set from final quasi-static analysis, or final results.



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5 ISO / SNAME COMPARISON

5.1 INTRODUCTION

5.1.1 A comparison of the input parameters, intermediate and final assessment results determined from assessment following the ISO 19905-1 and SNAME T&RB 5-5A Rev 3 approaches is summarised in the following sections:

5.2 FOUNDATION INPUT PARAMETERS

5.2.1 Geotechnical parameters calculated for the SNAME and ISO analyses are shown in the following table. Please note the difference in penetration for both the sand and clay cases is not modelled in the analysis, firstly because there is not enough leg length to model the SNAME penetration in clay and secondly, because it will provide for a more transparent comparison of the methods in later stages of the analysis.

5.2.2 Instead the SNAME analyses will be performed using the ISO penetrations; however the stiffness’s and capacities will be for the correct penetration.

Table 5-1 Foundation parameters

Site Assessment Parameter ISO SNAME Difference

Penetration (m) 0,91 0,95 0.04

Vertical foundation stiffness (te/m) 195753 195753 0

Horizontal foundation stiffness (te/m) 185603 185603 0

Rotational foundation stiffness (te.m/rad) 6494613 6921662 427049

Vertical foundation capacity (te) 15876 15876 0

Horizontal foundation capacity (te) 1905 1905 0

Site 1 (sand)

Moment foundation capacity (te.m) 16799 17343 544

Penetration (m) 42.02 46.40 4.38

Vertical foundation stiffness (te/m) 724642 761516 36874

Horizontal foundation stiffness (te/m) 497588 573765 76177

Rotational foundation stiffness (te.m/rad) 45065326 50231696 5166370

Vertical foundation capacity (te) 19695 15876 -3819

Weight of backfill (te) 4518 - -

Net vertical foundation capacity 15177 15876 700[1]

Horizontal foundation capacity (te) 5416 2401 -3015

Site 2 (clay)

Moment foundation capacity (te.m) 39481 44196 4715 [1] Buoyancy difference due to different penetration depths



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5.3 NATURAL PERIODS

5.3.1 The natural periods for the Super Gorilla on the sand foundation for both the pinned and fixity conditions are reported below:

Table 5-2 Natural periods

Site Fixity ISO Nonlinear Period (s) SNAME Nonlinear Period

(s)

Pinned 10,75

80% Rotational Fixity 8,04 7,97 Site 1 (sand)

100% Rotational Fixity 7,78 7,70

Pinned 10,30

80% Rotational Fixity 6,18 6,13 Site 2 (clay)

100% Rotational Fixity 6,07 6,04

Note, the periods reported are all sway periods.

5.3.2 The natural periods for the SNAME case are all marginally lower than those calculated using ISO. This is entirely due to the increased foundation rotational stiffness used in the SNAME analysis as shown in Table 5-1. It should be noted that the only difference between ISO and SNAME at this stage of the analysis is the foundation fixities.

5.4 SWAY STIFFNESS

5.4.1 The unit has been analysed with a unit loading of 2000t applied at the hull centre of gravity (CoG) for the purposes of the sway stiffness analysis. The following table shows the displacement of the hull CoG with differing levels of fixity both with and without P-Delta effects.

Table 5-3 Displacements and sway stiffness

Displacements (m) Sway stiffness (MN/m)

Site Foundation conditions

Excluding P-Delta effects ISO / SNAME

Including P-Delta effects ISO / SNAME

Excluding P-Delta effects ISO / SNAME

Including P-Delta effects ISO / SNAME

Pinned 2,054 2,409 9,552 8,144

Linear Fixity: 80% K3 (rot)

100% K3 (rot)

1,320 / 1,298 1,243 / 1,222

1,431 / 1,405 1,339 / 1,314

14,864 / 15,116 15,784 / 16,056

13,711 / 13,96414,653 / 14,932

Site 1 (sand)

Fixed 0,694 0,715 28,271 27,441

Pinned 2,08 2,34 9,675 8,385

Linear Fixity: 80% K3 (rot)

100% K3 (rot)

0,823 / 0,810 0,799 / 0,788

0,859 / 0,844 0,833 / 0,821

23,840 / 24,223 24,556 / 24,893

22,841 / 23,24623,553 / 23,898

Site 2 (clay)

Fixed 0,686 0,711 28,601 27,595

5.4.2 As with the natural period calculations the increase in sway stiffness for all of the SNAME analyses is due to the increased foundation rotational stiffness.



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5.5 WIND LOADS

5.5.1 Wind forces and moment arms are presented in Table 5-4 for 51,47 m/s wind speed and inclusive of the environmental load factor of 1,15. The moment arm is measured from the effective penetration.

Table 5-4 Wind loads

Force / Arm Site

Storm Direction

Leg Below Hull Hull Leg Above Hull

ISO 133,0kN / 140,25m 147,0kN / 171,85m 060˚

SNAME 151,4kN / 140,25m

8 868,4kN / 162,62m 172,7kN / 171,85m

ISO 132,2kN / 140,59m 147,0kN / 171,85m 090˚

SNAME 150,8kN / 140,59m

8 528,6kN / 162,64m 172,7kN / 171,85m

ISO 136,8kN / 140,67m 147,0kN / 171,85m

Site 1 (sand)

120˚ SNAME 154,3kN / 140,67m

7 382,6kN / 163,74m 172,7kN / 171,85m

ISO 96,9kN / 139,19m 59,7kN / 169,31m 060˚

SNAME 111,5 kN / 139,19m

8 808,8kN / 161.61m 70,1 kN / 169,31m

ISO 96,7kN / 139,97m 59,7kN / 169,31m 090˚

SNAME 111,7 kN /139,97m

8 471,7kN / 161,63 m 70,1 kN / 169,31m

ISO 98,3kN / 139,60m 59,7kN / 169,31m

Site 2 (clay)

120˚ SNAME 112,84kN / 139,60m

7 333,7kN / 162,73 m 70,1 kN / 169,31m

5.5.2 Note, the length of leg below the hull considered in the wind force calculations is calculated from the water surface to the keel level. The water surface elevation is different for each leg as it is calculated from the wave surface profile at the phase which corresponds to the maximum wave loading on the unit.

5.5.3 The wind loads presented above show identical hull wind loading between ISO and SNAME (single value presented), but that the wind load on the legs above and below the hull are lower for ISO than SNAME. This is due entirely to ISO recommending the use of a CD of 0,5 for leg drag above the waterline whereas SNAME recommends a CD of 0,65.



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5.6 WAVE LOADS

5.6.1 Wave forces and moments are presented in Table 5-5 for a 14,4 m significant wave height with a 16,6 s intrinsic period and a 1,492 m/s surface current. The forces and moments are inclusive of the environmental load factor of 1,15 with the moments calculated about the level of effective penetration.

Table 5-5 Wave / Current Loads

ISO SNAME

Storm

Direction Wave/Current Force (kN) [1]

Wave/Current Moment [1]

(MN.m)

Wave/Current Force (kN) [1]

Wave/Current Moment [1]

(MN.m)

060˚ 20 700 1 941,4 20 125 1 849,2

090˚ 21 045 1 964,6 20 355 1 883,8 Site 1 (sand)

120˚ 20 355 1 906,8 19 780 1 826,0

060˚ 21 045 2 157,7 20 240 2 052,1

090˚ 21 160 2 162,0 20 355 2 056,4 Site 2 (clay)

120˚ 20 470 2 101,6 19 780 2 000,2

[1] Reduction in current velocity (due to current blockage) has been omitted from both assessments - had this been included this would save approximately 10% on current loading, equivalent to approximately 5% on the overall wave/current loading.

5.6.2 The wave/current loads calculated for the unit are different between the ISO and SNAME analyses. This is due to the different calculation methods adopted with ISO using a kinematics reduction factor approach and SNAME using the traditional deterministic wave height approach.

5.6.3 It should also be noted that the effects of apparent (as opposed to intrinsic) wave theory have been incorporated into the ISO analysis, however the only difference introduced by this feature is the maximum and minimum loads occur at different times in the analysis due to the effects of apparent period.



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5.7 DYNAMIC AMPLIFICATION FACTORS (DAF’S)

5.7.1 The DAF’s shown below have been calculated for both the Sand and clay cases. Relative velocity effects have been included in the ‘mass’ analysis with the explicit damping ratio reduced from 7% to 4% (relative velocity effects account for 3%) in accordance with ISO/SNAME.

5.7.2 The following table shows the Overturning and Base Shear DAF’s calculated for each heading using a simulation length of 9hrs and a MPM exposure of 3hrs for the maximum hull weight case.

Table 5-6 Dynamic amplification factors (DAFs)

Overturning DAF Base Shear DAF Site Storm Heading

ISO SNAME ISO SNAME

060˚ 1,39 1,44 1,18 1,22

090˚ 1,35 1,38 1,16 1,19 Site 1 (sand)

120˚ 1,31 1,37 1,12 1,18

060˚ 1,50 1,49 1,34 1,33

090˚ 1,43 1,33 1,27 1,20 Site 2 (clay)

120˚ 1,38 1,33 1,26 1,23

5.7.3 GLND’s usual procedure for calculating weighted average DAF’s is to use 50% of the DAF for that heading and then add 25% from each of the DAF’s of the two adjacent headings (typically for 15-degree increments).

5.7.4 The weighted average DAF’s are shown in the following table.

Table 5-7 Weighted average DAFs

Overturning DAF Base Shear DAF Site

Storm Heading ISO SNAME ISO SNAME

060˚ 1,37 1,41 1,17 1,21

090˚ 1,35 1,39 1,15 1,20 Site 1 (sand)

120˚ 1,33 1,38 1,14 1,19

060˚ 1,46 1,41 1,30 1,26

090˚ 1,43 1,37 1,28 1,24 Site 2 (clay)

120˚ 1,40 1,33 1,26 1,21

5.7.5 It is clear from Table 5-7 that the SNAME DAF’s are slightly greater than the ISO DAF’s for the sand case and slightly less for the clay case. This is likely to be due to a combination of the following:

The use of different foundation stiffnesses for the ISO and SNAME analyses;

The effects of using the apparent wave period when generating the ISO storm as opposed to the intrinsic period used when generating the SNAME storm;

The inherent differences which occur when generating different storm data using different seeds.



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5.8 INERTIA LOADSETS

5.8.1 The following inertia loads were calculated and applied to the quasi-static models. Moments are calculated about the effective penetration.

Table 5-8 Inertia loadset

Inertia (Max hull weight) Inertia (Min hull weight) Site

Storm Heading

ISO SNAME ISO SNAME

Force kN 3519 4226 3933 4830 060˚

Moment kN.m 718325 758154 737739 832121

Force kN 3157 4071 3788 4478 090˚

Moment kN.m 687601 734667 707247 791180

Force kN 2850 3758 3257 4154

Site 1 (sand)

120˚ Moment kN.m 629231 693880 667367 730400

Force kN 6314 5262 5756 4655 060˚

Moment kN.m 994956 841345 905194 718221

Force kN 5925 4885 5311 4275 090˚

Moment kN.m 931935 760869 832239 658048

Force kN 5322 4154 4677 3758

Site 2 (clay)

120˚ Moment kN.m 842697 660064 736307 560055

5.8.2 The inertia loadset is calculated directly from the wave/current loads and the DAF’s, therefore the differences in both of these will be reflected in the inertia loads. Following from the calculated DAF’s the inertia loads for the SNAME analyses are greater than ISO for the sand case and less for the clay case.



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5.9 TOTAL QUASI-STATIC LOADING

5.9.1 The following tables show the overall loading of the subject jack-up for the quasi-static analysis. The total load includes wind, wave/current and inertia loads. Moments are calculated about the effective penetration.

Table 5-9 Total quasi-static loading

Total Loading (Max hull weight)

Total Loading (Min hull weight) Site

Storm Heading

ISO SNAME ISO SNAME

Force kN 33367 33544 33781 34148 060˚

Moment kN.m 4145851 4100424 4165265 4174390

Force kN 33010 33278 33641 33685 090˚

Moment kN.m 4083134 4056372 4102779 4112885

Force kN 30871 31248 31278 31643

Site 1 (sand)

120˚ Moment kN.m 3789363 3780084 3827498 3816604

Force kN 36324 34493 35766 33886 060˚

Moment kN.m 4607363 4346653 4517601 4223529

Force kN 35713 33894 35099 33283 090˚

Moment kN.m 4494279 4216186 4394584 4113366

Force kN 33284 31450 32639 31055

Site 2 (clay)

120˚ Moment kN.m 4168572 3883195 4062181 3783186

Note: Reduction in current velocity (due to current blockage) has been omitted from both assessments - had this been included this would save approximately 10% on current loading, equivalent to approximately 5% on the overall wave/current loading.

5.9.2 The following tables show the overall response of the subject Jack-Up including the overall base shear and overturning moments, Note the overturning moments are calculated about the point of effective penetration.

Table 5-10 Hull sway

Total Loading (Max hull weight)

Total Loading (Min hull weight) Site

Storm Heading

ISO SNAME ISO SNAME

060˚ 3,34 3,40 3,39 3,48

090˚ 3,30 3,40 3,33 3,40 Site 1 (sand)

120˚ 2,93 3,05 2,90 3,05

060˚ 3,04 2,88 2,93 2,57

090˚ 2,99 2,60 2,70 2,41 Site 2 (clay)

120˚ 2,52 2,20 2,36 2,05



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Table 5-11 Reactions in leg at base of rack chock - Maximum Hull Weight

ISO SNAME Site

Storm Heading Moment

kNm Shear

kN Axial kN

Moment kN,m

Shear kN

Axial kN

1430308 4189 23900 1477800 4816 24130

1421651 4334 24830 1473435 4966 25080 60

1605733 4047 147600 1648931 4426 147100

1405127 3280 64840 1460121 3966 64840

1454744 5371 -4504 1520382 6035 -4291 90

1533634 3268 135900 1592185 3764 135700

1300445 2632 101100 1366056 3171 101300

1317985 4933 -6698 1393017 5811 -7100

Site 1 (sand)

120

1290435 2929 101900 1356724 3451 102100

1419498 5405 25520 1340955 5059 27800

1413447 5576 26570 1336087 5226 28840 60

1562233 4232 143700 1476446 4034 139100

1386137 3939 64640 1218150 3451 64610

1449050 7645 -585 1257466 6456 7719 90

1469245 3011 131700 1295862 3599 123400

1195981 2276 97250 1050633 2342 93070

1275212 7905 467 1113439 6691 8813

Site 2 (clay)

120

1184993 2669 98030 1038950 2708 93860

Table 5-12 Reactions in leg at base of rack chock - Minimum Hull Weight

ISO SNAME Site


kNm Shear

kN Axial kN

Moment kN,m

Shear kN

Axial kN

1451137 4270 16990 1506310 4867 16610

1443638 4429 17830 1501662 5028 17470 60

1628448 4286 141100 1683155 4643 141800

1422096 3465 58100 1461094 4032 58100

1471831 5617 -10810 1520503 6155 -11050 90

1544649 3468 128600 1589241 3863 128800

1287317 2816 93770 1341386 3259 93890

1304350 4953 -12400 1367669 5700 -12620

Site 1 (sand)

120

1277091 3115 94520 1332748 3542 94630

1364854 5193 20260 1190276 4210 24820

1358723 5367 21200 1184347 4377 25750 60

1497335 4095 133600 1338385 4802 124500

1263110 3450 57760 1130124 3079 57760

1297129 6731 -1184 1155098 5884 5186 90

1336518 3843 118500 1198538 3859 112100

1116506 2177 88230 978002 2161 84310

1193290 7421 -2112 1039576 6230 5724

Site 2 (clay)

120

1105029 2593 88920 966406 2527 85010



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Table 5-13 Reactions at base of leg - Maximum Hull Weight

ISO SNAME Site


kNm Shear

kN Axial kN

Moment kN,m

Shear kN

Axial kN

80011 12038 41290 79994 12087 41520

83436 11946 41980 83374 12020 42230 60

1241 9392 164500 1716 9386 164000

140504 11621 82230 141209 11701 82230

7039 11841 12650 4925 12018 12860 90

10430 9544 152900 7252 9607 152600

127643 10141 118500 125482 10252 118700

1543 10785 10450 1156 10938 10050

Site 1 (sand)

120

128478 10004 118800 126402 10121 119000

385118 13689 43610 374057 13013 45890

385447 13586 44420 375388 12922 46690 60

1203 9007 161300 1002 8539 156700

365612 12801 82730 384212 11931 82700

385369 13815 17260 382037 12351 25570 90

29761 9115 149300 194815 9691 141000

288225 10665 115300 352310 10305 111200

390108 12119 18320 392080 10968 26660

Site 2 (clay)

120

287994 10503 115600 353122 10163 111500

Table 5-14 Reactions at base of leg - Minimum Hull Weight

ISO SNAME Site


kNm Shear

kN Axial kN

Moment kN,m

Shear kN

Axial kN

50202 12123 34380 44069 12235 34000

55070 12041 34980 49483 12178 34620 60

1103 9631 158000 1540 9693 158700

132604 11801 75490 133708 11811 75490

8286 12081 6340 6004 12179 6099 90

11170 9746 145500 8137 9747 145700

145980 10332 111200 145161 10451 111300

1703 10806 4750 1375 10933 4525

Site 1 (sand)

120

147159 10196 111400 146367 10321 111500

388102 13477 38350 381246 12266 42910

388629 13381 39050 382267 12181 43600 60

820 8870 151200 183097 9414 142100

377007 12311 75850 387708 11591 75850

391380 12888 16670 387532 11799 23040 90

190177 9943 136100 280649 9980 129700

316192 10572 106300 373698 10266 102400

390299 11637 15740 394001 10647 23570

Site 2 (clay)

120

319717 10432 106500 374693 10124 102600



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Table 5-15 Overall loading summary

ISO SNAME

Site Hull Weight Condition

Storm Heading

Base Shear kN

Overturning Moment kNm

Base Shear kN

Overturning Moment kNm

60 33370 4890000 33490 4862000

90 32970 4806000 33300 4793000 Maximum

120 30900 4407000 31280 4426000

60 33780 4849000 34090 4880000

90 33600 4764000 33710 4781000

Site 1 (sand)

Minimum

120 31310 4381000 31680 4392000

60 36270 5283000 34460 5001000

90 35680 5145000 33910 4799000 Maximum

120 33260 4694000 31410 4345000

60 35710 5107000 33860 4752000

90 35070 4925000 33290 4601000

Site 2 (clay)

Minimum

120 32610 4505000 31010 4171000

5.9.3 The above analysis results continue to show the same trends as those demonstrated by the DAF’s with the SNAME loads and reactions being greater than the ISO loads and reactions for the clay case but less for the sand case. It should be noted however that the loads and reactions are very similar between the two cases with a maximum difference in overturning moment of around 8% and a maximum difference in base shear of around 6%.

5.9.4 A reduction in current velocity (due to current blockage) has been omitted from the assessment - had this been included this would save approximately 5% on the overall wave/current loading.



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5.10 UTILISATION CHECKS

Summaries of the ISO vs SNAME assessment checks are presented in Table 5-16 and Note: The results presented above are based on adjusted leg-to-hull connection stiffness values for the purposes of benchmarking alone, and are therefore not representative of the Super Gorilla.

5.10.1 Table 5-17:

Table 5-16 Final assessment results Site 1 (Sand)

Criteria ISO SNAME ISO/SNAME

Hull Elevation (m) Airgap = 20,9 > Minimum clearance = 19,04


5,2 5,2 1,00


0,91 0,95 0,96

Utilisations Heading UC Heading UC -

Preload Capacity 60 1,16 60 1,17 0,99


60 1,63 60 1,82 0,90


- 0,1 - 0,13 0,77

Windward leg sliding

120 1,30 120 1,22 1,06


60 3,39 60 3,48 0,97

Leg chord strength 90 0,99 90 1,32 0,75

Leg brace strength 90 0,52 90 0,70 0,74


90 0,65 90 0,69 0,94


90 0,86 90 0,90 0,96

Max Overturning 120 0,98 120 0,99 0,99




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Table 5-17 Final assessment results Site 2 (Clay)

Criteria ISO SNAME ISO/SNAME

Hull Elevation (m) Airgap = 19,74 >= Minimum clearance = 19,74


2,2 -2,2 [1] 1,00


42,0 46,4 0,91

Utilisations Heading UC Heading UC -

Preload Capacity 60 1,13 60 1,12 1,01


60 1,45 60 1,50 0,97


- 7,2 - 6,3 1,14

Windward leg sliding

120 0,41 120 0,86 0,48


60 3,04 60 2,88 1,06

Leg chord strength 90 0,96 90 1,06 0,91

Leg brace strength 90 0,64 90 0,75 0,85


90 0,63 90 0,58 1,09


90 0,83 90 0,75 1,11

Max Overturning 120 0,87 120 0,79 1,10


[1] Although the penetrations were calculated differently between ISO and SNAME, both analyses used the same (ISO) penetration for the rest of the analyses.



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5.11 CONCLUSION

5.11.1 Comparison between the ISO and SNAME results above show that the loading condition and utilisation checks for the site 1 (sand) condition are similar, but slightly less onerous when following ISO recommendations to those of SNAME. For site 2 (clay) there is similarity between ISO and SNAME results, but ISO is more onerous than SNAME for preload and foundation bearing capacity, and leg and holding system strength checks.

5.11.2 It should be noted that the ISO and SNAME assessment approaches differ in only a few key areas, the aim of this assessment has been to compare the overall analysis methodology from beginning to end to asses the effect of the combination of these differences. Table 5-18 shows the main aspects of the analysis with the associated cause of the differences between ISO and SNAME.



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Table 5-18 Differences between ISO and SNAME

Analysis step

Difference between ISO and SNAME

Cause of difference

Natural periods and sway stiffness’s

Approx 1% Different spudcan fixities

Dynamic Amplification

Factors (DAF’s) Up to 17%

Different spudcan fixities

Use of apparent wave theory for ISO and intrinsic for SNAME

Wind loads Approx 15% Use of a different leg Cd values for ISO and SNAME

Wave/current loads

Approx 5% ISO utilises a kinematics approach whereas

SNAME adopts the deterministic wave height approach

Inertia loads Up to 28% Different DAF’s

Different wave/current loads

Quasi-static reactions

Up to 18%

Different wind loads

Different wave/current loads

Different inertia loads

Different foundation fixities and capacities

Different approach used to calculate Fr in the foundation iterations

Base shear and overturning moments

BS 6% OTM 8%

Different environmental loads

Different inertia loads

Different foundation fixities and capacities which effect the hull sway and hence the overturning moment.

Structural utilisations

Up to 11%

Different quasi-static reactions

Different approach used to assess the structural utilisations

In some cases different resistance factors.

Foundation utilisations

Preload 1% Bearing Capacity

12% Sliding >100%

Different quasi-static footing reactions

Different yield envelopes



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This report is intended for the sole use of the person or

company to whom it is addressed and no liability of any

nature whatsoever shall be assumed to any other party

in respect of its contents.

GL NOBLE DENTON

Signed: ____________________________________

Mark Hayward, MEng..

Senior Principal Engineer, Jack-up and Geotechnical Engineering

Countersigned: ______________________________________

Richard Stonor, B.Sc., Ph.D., C.Eng., MRINA

Manager, Jack-up and Geotechnical Engineering

Dated : London, 27th January 2011



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REFERENCES

[1] SNAME Technical and Research Bulletin 5-5A. ‘Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units”, 1st Ed., Rev 2., Jan 2002.

[2] ISO 19905-1, “Petroleum and natural gas industries - Site-specific assessment of mobile offshore units - Part 1: Jack-Ups”, Draft DIS, 12, 2009.

[3] Noble Denton Report No. L22909, “PHASE 1 BENCHMARKING OF ISO 19905-1.9 -COMPLETENESS CHECK”, Rev 1, Apr, 2009.



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Location DetailsName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/ADepth of water : 121.9 m (400 ft) 121.9 400

Jack-up Unit DetailsName : Generic Super GorillaDesign : Super Gorilla

Calculated Spudcan Reactions at Seabed LevelPreload reaction : 15,876 tonnes (35,001 kips) 15,876 35,001Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680

Expected Spudcan Tip Penetration 0.91 m (3 ft) 0.91 3

Average Soil Properties Used in Spudcan Penetration Analysis

' (kN/m3) cu top (kPa) cu bot (kPa) ' (o)1 0.0 SAND 11.0 - - 29.02 30.0 SAND 11.0 - - 29.03 - - - - - -4 - - - - - -5 - - - - - -6 - - - - - -7 - - - - - -8 - - - - - -

Spudcan Penetration Curve

spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 13-Apr-10

SPUDCAN PENETRATION ANALYSIS Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 Benchmarking

Layer Soil type

Spudcan Geometry

Average Soil PropertiesStarting Depth (m)

0

1

2

3

4

5

6

0 5000 10000 15000 20000 25000 30000

Vertical foundation load during preloading (tonnes)

Sp

ud

ca

n t

ip p

en

etr

ati

on

(m

)

0

2

4

6

8

10

12

14

16

18

0 10000 20000 30000 40000 50000 60000

Vertical foundation load during preloading (kips)

Sp

ud

ca

n t

ip p

en

etr

ati

on

(ft

)

Spu

dcan

pre

load

rea

ctio

n

Expected spudcan tip penetration = 0.91 m (3 ft).

Spu

dcan

stil

lwat

er r

eact

ion

Figure 6: ISO predicted leg penetration resistance curves for the Super Gorilla - SAND assessment case



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Location DetailsName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121.9 400

Jack-up Unit DetailsName : Generic Super GorillaDesign : Super GorillaMax. spudcan area : 243.2 m² (2618 ft²)Spudcan volume : 1164.8 m³ (41136 ft³)Length from tip to max. area : 1.2 m (4 ft 0 in)

Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,876 35,000Stillwater reaction 8,473 tonnes (18,680 kips) 8,473 18,680


Soil Parameters Used in Spudcan Penetration Analysis

Top of unit Base of unit ' (kN/m3) LB su (kPa) UB su (kPa) LB' (o) UB' (o)1 0.0 30.0 SAND 11.0 - - 29.0 29.0- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -


spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Checked: Appvd: RWPS Date: 03-Oct-10

SPUDCAN PENETRATION ANALYSIS Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 Benchmarking

Soil type

Spudcan Geometry

LayerDepth (m) Soil Properties

0

1

2

3

4

5

6

0 5000 10000 15000 20000 25000 30000


Sp

ud

ca

n t

ip p

en

etr

ati

on

(m

)

0

2

4

6

8

10

12

14

16

18

0 10000 20000 30000 40000 50000 60000


Sp

ud

ca

n t

ip p

en

etr

ati

on

(ft

)

Low er Bound

Average

Upper BoundSpu

dcan

pre

load

rea

ctio

n

Expected spudcan tip penetration= 1.0 m (3 ft).

Spu

dcan

stil

lwat

er r

eact

ion

Soil Profile

Figure 7: SNAME predicted leg penetration resistance curves for the Super Gorilla - SAND assessment case



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Location DetailsName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121.9 400


Calculated Spudcan Reactions at Seabed LevelPreload reaction : 15,876 tonnes (35,001 kips) 15,87635,001Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680

Parameters Used in V-H Calculations

Expected spudcan tip penetration : 0.91 m (3 ft) 3Maximum spudcan contact area : 156.3 m2 (1,682 sq.ft) 1,682Laterally projected spudcan area : 7.7 m2 (83 sq.ft) 83Steel/sand interaction factor, : 29.0 o 29.0cu at maximum bearing area, cuo : 0 kPa 0

cu at spudcan tip, cut : 0 kPa 0

Preload resistance factor, R,PRE : 1.10

Partial resistance factor horizontal capacity, R,Hfc : 1.25

Partial resistance factor foundation capacity, R,VH : 1.10

V-H Bearing Capacity Envelope

spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 03-Oct-10

Spudcan Geometry

Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 Benchmarking

V-H BEARING CAPACITY ENVELOPE

ISO DIS 19905-1

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

FH (tonnes)

Fv

(to

nn

es)

0

5000

10000

15000

20000

25000

30000

35000

0 500 1000 1500 2000 2500 3000 3500 4000

FH (kips)

Fv

(k

ips

)

Maximum Hull Weight

Minimum Hull Weight

Factored sliding capacity

Unfactored V-H capacity

Factored V-H capacity

Unfactored sliding capacity

Stillwater spudcan reaction (triangle)

Origin used for utilisation checks (diamond)

}

Figure 8: ISO predicted V-H Envelope for the Super Gorilla - SAND assessment case



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Location DetailsName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121. 400


Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,87635,000Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680


Expected spudcan tip penetration : 1.0 m (3 ft) 3Maximum spudcan contact area : 166.6 m2 (1,793 sq.ft) 1,793Laterally projected spudcan area : 8.2 m2 (88 sq.ft) 88Steel/sand interaction factor, : 29.0 o 29.0cu at maximum bearing area, cuo : N.A. #######

cu at spudcan tip, cut : N.A. #######

Preload resistance factor, P : 0.90

Sliding resistance factor, Hfc or Hfs : 0.80

Resistance factor for combined V-H loads, VH : 0.90


spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Appvd: RWPS Date: 03-Oct-10

Spudcan Geometry

Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 BenchmarkingV-H BEARING CAPACITY ENVELOPE

SNAME (Rev. 3 January 2008)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Horizontal load capacity (tonnes)

Ve

rtic

al

loa

d c

ap

ac

ity

(to

nn

es

)

0

10000

20000

30000

40000

50000

0 2000 4000 6000 8000 10000

Horizontal load capacity (kips)

Ve

rtic

al l

oa

d c

ap

ac

ity

(k

ips

)

Maximum Hull Weight

Minimum Hull Weight

Factored sliding capacity



Unfactored sliding capacity

Stillwater spudcan reaction

}

Figure 9: SNAME predicted V-H Envelope for the Super Gorilla - SAND assessment case



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Location Details Spudcan GeometryName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121.9 400


Calculated Spudcan Reactions at Seabed LevelPreload reaction : 15,876 tonnes (35,001 kips) 15,876 35,001Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680

Parameters Used in Fixity Calculations

Expected spudcan tip penetration : 0.91 m (3 ft) 3Maximum spudcan contact area : 156.3 m2 (1,682 sq.ft) 1,682Soil type : SandSoil backflow : YesBackflow unit weight: 11

Undrained shear strength, cu : N.A. kPa ######Overconsolidation ratio, OCR : N.A.Relative density, DR : 60 %Poisson's ratio, : 0.2

Calculated Vertical, Horizontal and Rotational Foundation Capacities

The following foundation capacities have been calculated in accordance with the 'ISO DIS 19905-1

These foundation capacities are for use with the ultimate vertical/horizontal/rotational capacityinteraction function for spudcan footings (Section A.9.3.3.2).

Vertical foundation capacity, VLO : 15876 tonnes (35,000 kips) 35,000

Horizontal foundation capacity, HLO : 1905 tonnes (4,200 kips) 4,200

Moment foundation capacity, MLO : 16799 tonne.m (121,508 kips.ft) 121,508

Calculated Initial Vertical, Horizontal and Rotational Foundation Stiffnesses

In accordance with ISO DIS 19905-1

Vertical foundation stiffness, K1 : 195,753 tonnes/m (131,540 kips/ft)

Horizontal foundation stiffness, K2 : 185,603 tonnes/m (124,720 kips/ft)

Rotational foundation stiffness, K3 : 6,494,413 tonne.m/rad (46,974,181 kips.ft/rad)

80% of Rotational foundation stiffness, K3 : 5,195,531 tonne.m/rad (37,579,345 kips.ft/rad)

Stiffness degradation factor, n 0.0

NOTE: In accordance with Clause A.10.4.4.1.2 the initial linearised rotational stiffness used in

detailed dynamic calculations may typically be taken as 80-100% of the values determined above.120,229 11,399 17,173,907 13,739,12131,540 124,720 46,974,181 579,345spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 13-Apr-10

Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 Benchmarking

SPUDCAN FIXITY PARAMETERS

Figure 10: ISO predicted ultimate capacities and fixities for the Super Gorilla - SAND assessment case



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Location Details Spudcan GeometryName : Generic medium dense sand location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121.9 400


Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,876 35,000Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680


Expected spudcan tip penetration : 0.95 m (3 ft) 3Maximum spudcan contact area : 166.6 m2 (1,793 sq.ft) 1,793

Soil type : SandSoil backflow : No

Undrained shear strength, cu : N.A. ######Overconsolidation ratio, OCR : N.A.Relative density, DR : 60 %Poisson's ratio, : 0.2


The following foundation capacities have been calculated in accordance with the 'SNAME TR&B 5-5AGuideline for the Site Specific Assessment of Mobile Jack-Up Units (Rev. 3 (Jan 2008)). Thesefoundation capacities are for use with the ultimate vertical/horizontal/rotational capacityinteraction function for spudcan footings (Section 6.3.4.2).





In accordance with SNAME T&RB 5-5A Section 6.3.4.3 (Rev. 3 (Jan 2008)):





NOTE: In accordance with SNAME T&RB (Rev. 3) recommendations (Section 6.3.4.6), the initial linearised rotational

stiffness used in detailed dynamic calculations may typically be taken as 80% of the values determined above.119,846 11,363 18,245,511 14,596,40131,540 124,720 50,064,475 051,580spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Appvd: RWPS Date: 03-Oct-10

Generic Super Gorilla at Generic medium dense sand location for ISO Phase 2 BenchmarkingSPUDCAN FIXITY PARAMETERS

Figure 11: ISO predicted ultimate capacities and fixities for the Super Gorilla - SAND assessment case



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Location DetailsName : Generic clay location for ISO Phase 2 BenchmarkingCoordinates : N/ADepth of water : 121.9 m (400 ft) 121.9 400


Calculated Spudcan Reactions at Seabed LevelPreload reaction VLo : 15,876 tonnes (35,001 kips) 15,876 35,001

Stillwater reaction : 8,473 tonnes (18,680 kips) 8,473 18,680


Average Soil Properties Used in Spudcan Penetration Analysis

' (kN/m3) cu top (kPa) cu bot (kPa) ' (o)1 0.0 CLAY 4.0 2.4 27.3 -2 19.0 CLAY 5.8 27.3 40.5 -3 29.0 CLAY 5.8 40.5 50.3 -4 36.5 CLAY 5.8 50.3 67.0 -5 45.0 CLAY 8.0 67.0 96.4 -6 60.0 CLAY 8.0 96.4 96.4 -7 - - - - - -8 - - - - - -


spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 31-Mar-10

SPUDCAN PENETRATION ANALYSIS Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking

Layer Soil type

Spudcan Geometry

Average Soil PropertiesStarting Depth (m)

0

5

10

15

20

25

30

35

40

45

50

0 5000 10000 15000 20000 25000 30000

VL = QV-WBF,0+BS (tonnes)

Sp

ud

ca

n t

ip p

en

etr

ati

on

(m

)

0

20

40

60

80

100

120

140

160

0 10000 20000 30000 40000 50000 60000

VL = QV-WBF,0+BS (kips)

Sp

ud

can

tip

pe

net

rati

on

(ft

)

Spu

dcan

pre

load

rea

ctio

n

Expected spudcan tip penetration = 42.02 m

Spu

dcan

stil

lwat

er r

eact

ion

Figure 12: ISO Predicted leg penetration resistance curves for the Super Gorilla - CLAY assessment case



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Location DetailsName : Generic clay location for ISO Phase 2 Benchmarking (SNAME)Coordinates : N/A N, N/A EDepth of water : 85.0 m (279 ft) 85.0 279

Jack-up Unit DetailsName : Generic Super GorillaDesign : Super GorillaMax. spudcan area : 243.2 m² (2618 ft²)Spudcan volume : 1164.8 m³ (41136 ft³)Length from tip to max. area : 1.2 m (4 ft 0 in)

Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,876 35,000Stillwater reaction 8,446 tonnes (18,621 kips) 8,446 18,621


Soil Parameters Used in Spudcan Penetration Analysis

Top of unit Base of unit ' (kN/m3) LB su (kPa) UB su (kPa) LB' (o) UB' (o)1 0.0 19.0 CLAY 4.0 2.4 - 27.33 2.4 - 27.33 - -2 19.0 29.0 CLAY 5.8 27.33 - 40.46 27.33 - 40.46 - -3 29.0 36.5 CLAY 5.8 40.46 - 50.3 40.46 - 50.3 - -4 36.5 45.0 CLAY 5.8 50.3 - 67 50.3 - 67 - -5 45.0 60.0 CLAY 8.0 67 - 96.4 67 - 96.4 - -- - - - - - - - -- - - - - - - - -- - - - - - - - -


spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Checked: Appvd: RWPS Date: 03-Oct-10

SPUDCAN PENETRATION ANALYSIS Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking (SNAME)

Soil type

Spudcan Geometry

LayerDepth (m) Soil Properties

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000 30000


Sp

ud

ca

n t

ip p

en

etr

ati

on

(m

)

0

20

40

60

80

100

120

140

160

180

0 10000 20000 30000 40000 50000 60000


Sp

ud

ca

n t

ip p

en

etr

ati

on

(ft

)Lower Bound

Average

Upper Bound

Spu

dcan

pre

load

rea

ctio

n Expected spudcan tip penetration= 46.4 m (152 ft).

Spu

dcan

stil

lwat

er r

eact

ion

Soil Profile

Figure 13: SNAME Predicted leg penetration resistance curves for the Super Gorilla - CLAY assessment case



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Location DetailsName : Generic clay location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 85.0 m (279 ft) 85.0 279


Calculated Spudcan Reactions at Seabed LevelPreload reaction VLo : 15,876 tonnes (35,001 kips) 15,87635,001



Expected spudcan tip penetration : 42.02 m (138 ft) 138Maximum spudcan contact area, A : 243.2 m2 (2,618 sq.ft) 2,618Laterally projected spudcan area, As : 99.4 m2 (1,070 sq.ft) 1,070Steel/sand interaction factor, : N.A. o 0.0cu at maximum bearing area, cuo : 59 kPa (1,232 lb/sq.ft) 1,232

cu at spudcan tip, cut : 61 kPa (1,274 lb/sq.ft) 1,274

Preload resistance factor, R,PRE : 1.10

Partial resistance factor horizontal capacity, R,Hfc : 1.56

Partial resistance factor foundation capacity, R,VH : 1.15


spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 03-Oct-10

Spudcan Geometry

Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking

V-H BEARING CAPACITY ENVELOPE

ISO DIS 19905-1

0

5000

10000

15000

20000

25000

0 1000 2000 3000 4000 5000 6000

Fh (tonnes)

Fv

(to

nn

es)

0

10000

20000

30000

40000

50000

0 5000 10000 15000 20000

Fh (kips)

Fv

(k

ips

)

Maximum Hull Weight

Minimum Hull Weight

Fac

tore

d sl

idin

g ca

paci

ty



Unf

acto

red

slid

ing

capa

city

Stillwater spudcan reaction (triangle)

Origin used for utilisation checks (diamond)0,5QV/R,VH

}

Figure 14: ISO predicted V-H Envelope for the Super Gorilla - CLAY assessment case



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Location DetailsName : Generic clay location for ISO Phase 2 Benchmarking (SNAME)Coordinates : N/A N, N/A EDepth of water : 85.0 m (279 ft) 85.0 279


Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,87635,000Stillwater reaction : 8,446 tonnes (18,621 kips) 8,446 18,621


Expected spudcan tip penetration : 46.4 m (152 ft) 152Maximum spudcan contact area : 243.2 m2 (2,618 sq.ft) 2,618Laterally projected spudcan area : 52.8 m2 (568 sq.ft) 568Steel/sand interaction factor, : N.A. 0.0cu at maximum bearing area, cuo : 67 kPa (1,399 lb/sq.ft) 1,399

cu at spudcan tip, cut : 70 kPa (1,462 lb/sq.ft) 1,462

Preload resistance factor, P : 0.90

Sliding resistance factor, Hfc or Hfs : 0.64

Resistance factor for combined V-H loads, VH : 0.85


spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Appvd: RWPS Date: 03-Oct-10

Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking (SNAME)V-H BEARING CAPACITY ENVELOPE

SNAME (Rev. 3 January 2008)

Spudcan Geometry

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 500 1000 1500 2000 2500 3000 3500 4000

Horizontal load capacity (tonnes)

Ve

rtic

al lo

ad

cap

acit

y (t

on

nes

)

0

5000

10000

15000

20000

25000

30000

35000

0 1000 2000 3000 4000 5000 6000 7000 8000

Horizontal load capacity (kips)

Ver

tic

al lo

ad

cap

acit

y (k

ips)

Maximum Hull Weight

Minimum Hull Weight

Fac

tore

d sl

idin

g ca

paci

ty



Unf

acto

red

slid

ing

capa

city

Stillwater spudcan reaction

}

Figure 15: SNAME predicted V-H Envelope for the Super Gorilla - CLAY assessment case



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Location Details Spudcan GeometryName : Generic clay location for ISO Phase 2 BenchmarkingCoordinates : N/A N, N/A EDepth of water : 121.9 m (400 ft) 121.9 400


Calculated Spudcan Reactions at Seabed LevelPreload reaction VLo : 15,876 tonnes (35,001 kips) 15,876 35,001



Expected spudcan tip penetration : 42.02 m (138 ft) 138Maximum spudcan contact area : 243.2 m2 (2,618 sq.ft) 2,618Soil type : ClaySoil backflow : YesBackflow unit weight: 5.80

Undrained shear strength, cu : 64 kPa (1,334 lb/sq.ft) 1,334Overconsolidation ratio, OCR : 1.1Relative density, DR : N.A. %Poisson's ratio, : 0.5Adhesion factor, : 1.0


The following foundation capacities have been calculated in accordance with the 'ISO DIS 19905-1

These foundation capacities are for use with the ultimate vertical/horizontal/rotational capacityinteraction function for spudcan footings (Section A.9.3.3.2).

Vertical foundation capacity, Qv : 19695 tonnes (43,421 kips) 43,421Horizontal foundation capacity, QH : 5416 tonnes (11,941 kips) 11,941

Moment foundation capacity, QM : 39481 tonne.m (285,567 kips.ft) 285,567


In accordance with ISO DIS 19905-1





Stiffness degradation factor, n 0.0

NOTE: In accordance with Clause A.10.4.4.1.2 the initial linearised rotational stiffness used in

detailed dynamic calculations may typically be taken as 80-100% of the values determined above.97,907 66,092 53,705,442 42,964,35486,937 334,363 325,958,121 766,497spud_pen ISOv0 W.S. 05-130553 Calc: DHE Appvd: MJRH Date: 31-Mar-10

Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking

SPUDCAN FIXITY PARAMETERS

Figure 16: ISO predicted ultimate capacities and fixities for the Super Gorilla - CLAY assessment case



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Location Details Spudcan GeometryName : Generic clay location for ISO Phase 2 Benchmarking (SNAME)Coordinates : N/A N, N/A EDepth of water : 85.0 m (279 ft) 85.0 279


Calculated Spudcan Reactions at Predicted PenetrationPreload reaction : 15,876 tonnes (35,000 kips) 15,876 35,000Stillwater reaction : 8,446 tonnes (18,621 kips) 8,446 18,621


Expected spudcan tip penetration : 46.4 m (152 ft) 152Maximum spudcan contact area : 243.2 m2 (2,618 sq.ft) 2,618

Soil type : ClaySoil backflow : Yes

Undrained shear strength, cu : 72 kPa (1,510 lb/sq.ft) 1,510Overconsolidation ratio, OCR : 1Relative density, DR : N.A.Poisson's ratio, : 0.5


The following foundation capacities have been calculated in accordance with the 'SNAME TR&B 5-5AGuideline for the Site Specific Assessment of Mobile Jack-Up Units (Rev. 3 (Jan 2008)). Thesefoundation capacities are for use with the ultimate vertical/horizontal/rotational capacityinteraction function for spudcan footings (Section 6.3.4.2).





In accordance with SNAME T&RB 5-5A Section 6.3.4.3 (Rev. 3 (Jan 2008)):





NOTE: In accordance with SNAME T&RB (Rev. 3) recommendations (Section 6.3.4.6), the initial linearised rotational

stiffness used in detailed dynamic calculations may typically be taken as 80% of the values determined above.110,841 74,823 60,800,007 48,640,00511,715 385,553 363,326,549 661,239spud_pen v2.1 Soils Database Ref. W.S. 05/130553 Calc: DHE Appvd: RWPS Date: 03-Oct-10

Generic Super Gorilla at Generic clay location for ISO Phase 2 Benchmarking (SNAME)SPUDCAN FIXITY PARAMETERS

Figure 17: SNAME predicted ultimate capacities and fixities for the Super Gorilla - CLAY assessment case (Including SAGE effects)



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Appendix A - Comments submitted to ISO



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1 2 (3) 4 5 (6) (7)

MB1

Clause No./ Subclause No./ Annex (e.g. 3.1)

Paragraph/ Figure/Table/Note (e.g. Table 1)

Type of com-ment2

Comment (justification for change) by the MB Proposed change by the MB Secretariat observations on each comment submitted

UK List of symbols for A9

ed as and bs are both defined as “bearing capacity squeezing factor” - presumably can’t have two identical descriptions for different parameters

Rename bs to “layer thickness squeezing factor”


ed Definition of CHdeep seems to have been corrupted Replace with definition given in A.9.3-16


ed Definition of D - add cross-reference to Figure 9.3-3 Add cross-reference


ed Equation for dc is only given in list of symbols and not in Appendix A.9

Include equation given for dc in A.9.3.2.2


ed Definition of FM as an “applied moment force” is incorrect - should be “applied moment”

Re-define FM as “applied moment”


ed Definition of fr Redefine more specifically as “Spudcan rotational stiffness reduction factor”


ed Definition of G Redefine more specifically as “soil shear modulus”


ed Definition of Hcav - use of “limiting” is not particularly clear or helpful

Remove “limiting”

Key:

1 MB = Member body (enter the ISO 3166 two-letter country code, e.g. CN for China; comments from the ISO/CS editing unit are identified by **) 2 Type of comment: ge = general te = technical ed = editorial NOTE Columns 1, 2, 4, 5 are compulsory.



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Ed I note that the definition of ‘a’ used in Annex E1 is not the same as that definite in Appendix 9 - do they need to be differentiated, or should there also be a list of symbols for each Annex? Presently some symbols used in Annex E are not defined in the list of symbols.


Ed - Add definition for ns “load spread factor for projected area method”


Ed Definition of pa Provide value of 101,3 kPa in definition


Ed Definition of QMp erroneously refers to QMsv Replace QMsv with QMpv


Ed Definition of QMps refers to “fully seated spud conditions” Replace with “full contact of the entire underside of the spudcan with the sea floor”


Ed Definition of qo as “surface bearing resistance” needs rephrasing

Redefine qo as “vertical bearing capacity of spudcan for full contact of the underside of the spudcan with the sea floor” - in any case it should be Qo as in Annex E3 and not qo

UK List of symbols for A9 / A.9.3.2.6.4

Ed Definition of qmax and qo are potentially ambiguous Replace with “maximum vertical bearing capacity at d=dcrit, refer to Annex E3” - replace with Qpeak as in Annex E3


Ed Definition of rf is potentially ambiguous/unhelpful Suggest replacing definition with “normalised ratio of factored foundation action to the unfactored foundation bearing capacity envelope”


Ed Definition of sc - just give a value of 1.18 (=6.05/(2+)) as the values of Nq given in the document inherently include shape factor (see A.9.3.2.4) - i.e. there is the potential for confusion

Replace with sc=1.18



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Ed Definition of VLo erroneously refers to 3.69 Replace 3.69 with presumably 3.51


Ed Definition of Vsw - I do not understand the need to refer to ‘a solid rock foundation’ - what is the significance of this?

Replace part in brackets with: (the footing reaction to the self-weight of the jack-up unit, plus the reaction due to the submerged weight of any backfill on the spudcan, less the reaction due to the submerged weight of the soil displaced by the spudcan)


Ge/Ed Generally replace “effective submerged weight” with simply “submerged weight”


Ed Definition of alpha - alpha can be any value between 0 and 1.0, therefore providing these two values is potentially misleading

Replace values with a reference to A.9.3.3.3 for further details


Ed Definition for Replace with “rate of increase in undrained shear strength with depth”


Ed Definition for - presentation of units (degrees) is inconsistent with that for delta

Either put degrees in brackets or after a hyphen depending on ISO protocol (should units even be in list of symbols?)

UK A9 Ge There are various symbols and definitions of bearing capacity and footing loads - the use of Fv,in seems unnecessary and presumably can be replaced with VLo

Replace all instances of Fv,in with VLo ?

UK A.9.3.2.1.1 Ge No mention as to whether upper and lower bound soil strength profiles should be considered in spudcan penetrations analyses, or only ‘best estimate’

Upper and lower bound profiles should be considered.

UK A.9.3.2.1.1 Equation A.9.3-1.a

Te The equation does not include spudcan buoyancy contribution due to the volume of the spudcan within the soil below the max. plan area level

Panel 4 generally need to review figures, equations and descriptions involving backflow and spudcan buoyancy within Appendix 9. Even at the

f th i d b d t th



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UK A.9.3.2.1.1 Equation A.9.3-1.b

Te The weight of backflow soil, defined in Equation A.9.3-2, includes all volume between lowest point of max. area and the base of the crater (and would hence include the spudcan volume above lowest point of max. area, whereas this volume is also included in Bs term) - clarification is needed as this could leave the potential for a significant “double-dip” if not treated carefully.

UK A.9.3.2.1.3 Ed “The soil beneath the spudcan fails as the foundation is loaded during preloading until equilibrium is achieved at the end of the preloading operation”

Replace with “The spudcan will penetrate into the seabed during preloading until the spudcan’s bearing capacity achieves equilibrium with the applied preload”

UK A.9.3.2.1.4 Ed “Backflow is the soil that flows from beneath the spudcan, around the sides, and onto the top and is more likely to occur in clays than in sands. Backflow can occur at shallow penetrations, but is more likely to occur at deeper penetrations. In very soft clays complete backflow is likely to occur. In firm to stiff clays and granular materials, where spudcan penetration is expected to be small, the possibility of backflow diminishes. In general, backflow due to additional penetration during elevated operations is not expected to occur. If it is predicted, the effects should be taken into account.” - backflow occurs straightaway in sand and depends on penetration depth in clays - can be rephrased to be more clear/efficient.

Replace with “Backflow is the soil that flows from beneath the spudcan, around the circumference and on to the top of the spudcan during penetration into the seabed. This occurs immediately in sands, should sufficient penetrations occur, and after a certain penetration depth in clays, which can be determined using the method described below. ”

UK A.9.3.2.1.4 Figure A.9.3-6

Ed Key below Figure A.9.3-6 refers to ‘e’ for the cavity however I cannot see where this is used in either figure.

Remove?

UK A.9.3.2.1.4 for example

Te Although reference is made to infill, no guidance is provided for quantifying infill. For example if there is a layer of sand at the seabed surface should it be assumed that this will subsequently completely infill the crater if the seabed is shown to be mobile? (this could result in a very significant additional vertical footing load)

Guidance needed from Panel 4

UK A.9.3.2.1.4 Eqn A.9.3-2 & Fig A.9.3-5

te The definitions of Hcav in Equation A.9.3-2 and Fig A.9.3-5 suggest that a portion of the spudcan volume would be included in calculating the weight of backfill.

See earlier comment regarding spudcan volume and backfill



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UK A.9.3.2.1.4 Ed “the penetration resistance offered by a localised backflow mechanism becomes independent of depth of penetrations exceeding B”

Clarify that this penetration refers to D and not tip penetration depth. This statement of fact needs a reference.

UK A.9.3.2.1.4

Te “the penetration resistance offered by a localised backflow mechanism

becomes independent of depth of penetrations exceeding B” - this appears to be inconsistent with both Skempton’s depth factor equation and Houlsby & Martin’s BC factors which are recommended in the ISO.

Panel 4 should agree the point at which the backflow mechanism becomes independent of penetration depth

UK A.9.3.2.1.4 Ed Reference to Table A.9.3-1 should read Table A.9.3-2 Correct Table reference

UK A.9.3.2.1.4 Figure A.9.3-6

Ed More details are required in order for the user to calculate Hcav - the plot in Figure A.9.3-6 is not helpful in itself, rather the equation should be written in the text along with some explanation of how to obtain Hcav

Propose using the text from the original OTC paper:





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UK A.9.3.2.1.4 Figure A.9.3-6

Symbol ‘X’ in the key that refers to undrained shear strength

Should be replaced with Su

UK A.9.3.2.2 Table A.9.3-2

Ed The caption should emphasise that these assume homogeneous strength.

Replace caption with “Bearing capacity factors for rough circular plate on homogeneous clay”

UK A.9.3.2.2 Ed Cross reference to A.9.3.2.8 before Table A.9.3-2 should be replaced with A.9.3.2.6

Replace cross-reference

UK A.9.3.2.2 Table A.9.3-2

Te Presumably these values (and those in Annex E1) can be interpolated; is the error involved in linearly interpolating Houlsby & Martin’s tabulated values in Annex E1 acceptable for other depth and values? (i.e. you would need to interpolate using four tabulated values in order to find the Ncscdc for a combination of D/B and values that are not explicitly given in the tables).

Guidance required from Houlsby

UK A9.3.2.2 Te It is not clear whether Houlsby & Martin’s values can be used for a clay layer that is not at the surface

Guidance needed from Houlsby - Can it be used? if so, would Sum refer to the undrained shear strength at the top of the layer or still at the sea floor surface?

UK A9.3.2.2 / Annex E1

Te Edwards et al. (Géotechnique 2005 No. 55, No. 10) showed that Houlsby & Martin’s bearing capacity factors values are notably lower (i.e. less accurate) than the upper and lower bound solutions derived by Martin and FE data.

The likely errors involved in using Houlsby & Martin’s values compared to the latest research should be quantified and noted in the text, else refer to values in Edwards and Martin’s papers

UK A.9.3.2.2 Te No guidance is provided on how to average undrained shear strength with depth if a sand layer is encountered.

Suggest adding guidance from Panel 4 (Dave Menzies?)

UK A9.3.2.4 Eq. A.9.3-5 Te Depth factors are not included in this equation - can occasionally be relevant for very loose sand locations

Add depth factors



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UK A.9.3.2.6.4 Te Equation given in SNAME for use with projected area method is floating at the bottom of the diagram

Add equation properly and add explanation and notes to diagram as in SNAME:

UK A.9.3.3.1 Ed “the maximum moment and horizontal capacities which, with the vertical capacity, are the principal coordinates of the yield interaction surface.”

Suggest replacing with “the maximum moment and horizontal capacities which, with the vertical capacity, are the principal dimensions of the yield interaction surface.”

UK A.9.3.3.1 Ed “The shape of the yield surface for shallow foundations is parabolic”

Change relevant instances of “parabolic” to “paraboloidal”, also “elliptic” to “ellipsoidal” as the yield surface is 3-dimensional

UK A.9.3.3.1 Ed - Change cross-reference to A.9.3.2.2.5 to A.9.3.2.1.5

UK A.9.3.3.1 Ed “load-penetration equations given in A.9.3.2.3 through A.9.3.2.8” - incorrect sections

Replace with “load-penetration equations given in A.9.3.2.2 through A.9.3.2.6”

UK A.9.3.3.1 Figure A.9.3-12

Ed Is it appropriate to refer to V, H and M? Replace with QV, QH and QM?

UK A.9.3.3.2 Equation A.9.3-16

Te The choice of whether to use an averaged Su or modified bearing capacity factor in the spudcan penetration calculations will lead to different ‘b’ values for horizontal capacity.

Su in the ‘b’ equation should be replaced with Suo - the undrained strength at the depth of the max. plan area.





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UK A.9.3.3.2 Te “with backfill” formulae for Fv need clarification as to how to calculate backfill appropriately (see earlier comments)


Te Qvnet formula (after second equals sign) - this Qv-Ap’o definition ignores cavity depth and spudcan buoyancy and is potentially confusing and could lead to misunderstandings. (note Figure A.9.3-7 defines p’o as the overburden pressure without consideration of spudcan buoyancy and cavity depth).

Remove Qvnet = Qv-Ap’o definition and corresponding “Note 2”.


Ed definition of Su,a has a spelling mistake: “sstrength” Replace “sstrength” with “strength”

UK A.9.3.3.2 Te As definition - should this be the whole laterally projected area of the spudcan or just the lower portion in contact with the non-backflow soil?

Clarification required from Templeton

UK A.9.3.4.1 Ed Description of elastic solutions can be more specific to emphasise that these are derived for rough-based circular footings with a flat base (as opposed to a typical spudcan)

Replace “elastic solutions for a rigid disk” with “elastic solutions for a rough, flat-based rigid disk”

UK A.9.3.4.1 Te With reference to soil shear modulus, G: “An upper or lower bound value should be selected” - when should you use which?

Add clarification from Panel 4

UK A.9.3.4.1 Te There is no mention of the cross-coupling stiffness, K4 which links horizontal footing displacements and footing rotations to moment and horizontal loads respectively. Consideration of K4 is required for all conical footings, and for flat-based footings for v<0.5

Furthermore the choice of seabed reaction point in A.8.6.2 will have an influence on the K4 values.

This should at least be discussed if K4 is not to be specified.

The guidance provided in A.8.6.2 for the determination of the seabed reaction point should be reviewed (suggest by Houlsby and/or Martin) and included in discussion.

UK A.9.3.4.2.1 Table A.9.3-4

Te The data presented for the depth factors are not from Bell’s thesis (as referenced) and are for Poisson’s ratio = 0.0 - these are not appropriate for soils

Replace values in table with the tables for various Poisson Ratios provided in SNAME (2008)

UK A.9.3.4.2.2 Te “cyclic degradation reduces the horizontal bearing capacity by 30%” - surely this should be in the section on bearing capacities, not foundation stiffnesses.

Move or copy the part referring to bearing capacities to A.9.3.3.2



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UK A.9.3.4.2.3 Eqn A.9.3-34

Ed The two terms in the denominator should be added, not subtracted.

UK A.9.3.4.3 Ed It would seem to make more sense for A.9.3.4.3 to appear before A.9.3.4.2, as G is required for the expressions in A.9.3.4.1. K1, 2 and 3 should be determined before stiffness depth factors, etc. are applied

Move A.9.3.4.3 to before A.9.3.4.2

UK A.9.3.4.3 Te The guidance provided for IrNC is unclear - when, for example, should the data in Fig A.9.3-12 actually be used?

Clarification required from Panel 4 (Andersen?)


Ed The symbol for overconsolidation ratio in is still ‘O’ instead of ROC

Replace ‘O’ with ROC

UK A.9.3.4.3 Te “except in areas with carbonate clays or clayey silts…” Panel 4 should provide comments/guidance for such situations

UK A.9.3.4.3 Eq. 9.3-36 Te Is the Su value referred to different from Su in Figure A.9.3-12? (which is from a Direct Simple Shear test)

Clarification required and/or consistency between figure and text (Andersen?)

UK A.9.3.4.3 and A.9.3.4.4

Ed Is it intended for the paragraph “The recommendations given above… …upper-bound values of G” to be duplicated in both A.9.3.4.3 and A.9.3.4.4?

Suggest rationalising

UK A.9.3.5.3 Te Should the factored sliding line should continue above Fv/Qv=0.5 until it meets the factored V-H envelope? Otherwise the factored sliding line will not touch the factored V-H envelope and the two factored envelopes (sliding and V-H) will be disjointed.

Propose that the factored sliding line should continue until it touches factored V-H envelope

UK A.9.3.5.3 Ed - Suggest adding "and in A.9.3.3.3 for Fv < 0.5 Qv" to the end of the first sentence

UK A.9.3.6.1 A.9.3-14 te Flow chart does not mention the Nonlinear continuum foundation model described in A.9.3.4.2.5

Suggest adding reference to A.9.3.4.2.5 in rectangular box with A.9.3.4.2.4

UK A.9.3.6.2 Table A.9.3-5

te Appears to be an error in equation for Clay with embedment less than 1.0 times spudcan diameter as the two expressions for clay appear not to be equal for D/B=1.0

Suggest checking with Templeton



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UK A.9.3.6.2 ed The description “is small” needs to be specifically linked to Table A.9.3-5 (at least 2 occurrences)

Replace “is small” with “less than the corresponding limiting horizontal reaction given by Table A.9.3-5”

UK A.9.3.6.2 te It is not clear the technical basis for the following statement: “Additional penetration can increase the soil resistance, but to increase the horizontal capacity to 0,1VLo the additional penetration is about 10% of the spudcan diameter and outside tolerable limits.” Surely this depends on , , etc.

Replace with “Although additional penetration can increase the soil resistance, it is possible for such additional penetrations to exceed those tolerable by the unit.”

UK A.9.3.6.4 Eq. A.9.3-43 Ed The definition and position of the resistance factor is confusing - if it is a resistance factor surely it should be multiplied by the resistance?

According to the text the resistance factor is used to divide the capacities, however in the equation it is used to multiply the actions - although strictly correct according to the definition it is rather confusing!

Suggest using rewriting equation such that the capacities and origins are each individually divided by the resistance factor and not the environmental response point.

UK A.9.3.6.4 Eq. A.9.3-43 Ed The symbol QVH,f appears in the equation but is not defined until after Figure A.9.3-15

Move definition from below Figure A.9.3-15 to below Eq. A.9.3-43

UK A.9.3.6.4 Te The definition of QVH is not clear, this is apparently the point at which the vector intersects the unfactored envelope, so how can it be calculated by dividing the capacities from A.9.3.5 by the resistance factor?!

Section A.9.3.6.4 needs a re-write - it is presently extremely confusing !

UK A.9.3.6.4 Figure A.9.3-15

Te Example V-H envelope is only presented for sand Provide example ‘clay’ envelope

UK A.9.3.6.4 Figure A.9.3-15

Te - Include in the example V-H envelope some laterally projected area component for sliding line

UK A.9.3.6.4 Figure A.9.3-15

Te I am not completely clear how the V-H envelope would look like for a spudcan that penetrates through very soft clay into underlying sand - what would it look like for V/Qv<0.5? There would be significant backflow weight, hence would the ellipse shift upward along the vertical load axis?

Panel 4 should review this situation to check that a sensible V-H envelope is produced by the present guidelines

UK A.9.3..6.4 Figure A.9.3-15

Ed Spelling errors Change both instances of “multipiled” to “multiplied”



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UK A.9.3..6.4 Figure A.9.3-15

Ed Layout is unclear for definition of QVH,f

UK A.9.3.6.4 Figure A.9.3-15

Te - Add points indicating typical range of Vsw values or a figure to explain the “Note” below Figure A.9.3-15

UK A.9.3.6.6 Te “The displacement associated with this "virtual" preload is then obtained from the load-penetration curve”

If upper and lower bound load-penetration curves are produced, should additional settlements be determined using LB curve, steepest of all 3 or only with the best-estimate curve

Propose using the steepest of all three curves and include this recommendation in the text.

UK A.9.3.6.7 Ed Typographical error: “The settlements due to bearing capacity failure during to preloading”

Replace with “The settlements due to bearing capacity failure during preloading”

UK A.9.4.2 Te No explicit mention of ‘rack phase differences’ here Add reference to RPDs or suggest references

UK A.9.4.5 Te Add a further recommendation regarding mitigation of leg extraction difficulties.

“It is prudent, and a matter of good practice, to ensure that a unit’s jetting system is fully functional prior to installation at a location where penetration into cohesive soils is predicted”

UK A.9.4.6 Ed “References:” appears at end of section Remove

UK A.10 A.10.4.4.1.2 te Currently this part of the document specifies an initial linearised rotational stiffness of 80-100% of the calculated value. Additional guidance is requested to clarify when it would be appropriate to use 100% initial linearised stiffness.

Add additional guidance (although from which Panel, I’m unsure)

UK A.12 A.12.5.2.2 ed The reference to A.12.5.2.3 should be to A.12.5.2.4 Correct the reference

UK A.12 A.12.6.3.2 ed In the descriptions of Mby and Mbx there are references to equations A.12.6-29 and A12.6-28 respectively. These references do not exist.

Correct these references to A.12.6-25 and A12.6-24 respectively.

UK Annex E1 Te Comments required stating that backflow has not been modelled by Houlsby & Martin due to the boundary conditions used in their analysis - hence the bearing capacity factors may not be suitable for penetrations approaching and beyond Hcav

Propose Houlsby adds comments to that effect



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UK Annex E1 Figure E.1-1 Ed Bearing capacity defined as Q in the Key to Figure E.1-1 but referred to as Fv in the tables.

UK Annex E1 Figure E.1-1 Ed Key below Figure E.1-1 states “NOTE Note: based on”… Remove one of the ‘Note’s’

UK Annex E2 Ed Use of symbol and arrow for FV,in is inconsistent with rest of document

Replace FV,in with Qvo

UK Annex E3 Te/Ed Generally this section seems out-of-place in the ISO, for example many such sections could also be introduced for various aspects of geotechnical analysis such as clay overlying clay, scour, etc. etc.

If it is intended to be kept then it needs significant revision which includes references to Lee et al. 2009 OTC paper and a detailed description of Teh’s proposed method of analysis

Propose removing this section and simply adding in Appendix A.9.3.2.6.4 references to the relevant technical papers

UK F.3 Para 1 ed “Sections that are not been” Replace with “Sections that have note been”

UK F.3 - te P should be changed to Pu to be consistent with the rest of the document in this whole section

Implement the proposed change

UK F.3 - te Prismatic member checks. P/Py should be capped at 1.00 for the surface interaction equations to prevent the equations from going out their intended range

Add additional limits to the existing equations

UK F.3 - te The surface interaction equations should include a P/Py term. Otherwise the utilisation is only related to bending and not axial loads.

Discussion is required to decide how the P/Py term should be incorporated into the equations.

UK F.3 Fig F.3-3 ed “When Mx 0:” Replace with “When Mz 0:”

UK F.3 Fig F.3-4 te It would be useful to explain the meaning of K as it is described in Alan Dyer’s thesis

Add explanation for K

UK A.7.3.2.3 Eq A.7.3-2 note

Ed A typo in De = slD /( i

2I It should be slD /i

2I or slD /)( i

2I

UK A.12.3.4.3 Table 12.3-1 Te Effective width calculations for Slender Components, a) Compression flange internal components and c) Web internal components under bending and/or compression, are plausible.

“a) Compression flange internal components” is considered to be redundant.





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UK A.6.4.2 General Ed No reference to qualifying / sense-checking supplied metocean data

Include one-liner to check data-sets provided satisfy waveheight & period relationships

UK A.6.4.2.7 Para 1 Te Reference to gamma of 1.0 Make clear that this if for DAF calculation only, and that a default gamma of 3.3 is used for wave period relationship calculations (as per after gamma vs Tp/Tz table.

UK A.6.4.2.7 Para 4 Te Advice for Gamma’s when using JONSWAP presented - no other guidance given for other spectrums

Include guidance

UK A.6.4.6.2 Vz definition Te Vz defined w.r.t ‘mean’ water level - surely this should be storm water level (LAT+t+s) assessed ?

Amend MWL to SWL

UK A.7.3.2.4 Para 3 Ed Reference to MWL inconsistent with MSL in same paragraph

Amend to MSL

UK A.7.3.4.1 Te No guidance given on wind on legs below the hull - assume to be determined based on peak wave-phase loading condition (reduced exposed leg length) rather than still-water leg length

Include guidance

UK A.7.3.4.2 Table A.7.3-5

Te Shape coefficients for leg sections recommend using tubular CDi of 0.5. GLND surprised by this change from SNAME’s use of CDe based on ‘smooth’ coefficient of 0.65.

Review decision for change - possible impact is 10% reduction of wind loads on legs when using ISO compared to SNAME.

UK A.8.5.7 Para 1 Ed The reference to A.8.5.7 refers to its own paragraph. Either delete or change reference to A.8.2.3

UK A.8.2.3 Ed No reference to mass modelling in any of the modelling options from fully detailed FE model to equivalent stick model

Suggest add reference to 8.7 (mass modelling) and A.8.7.

UK 8.7 (& A.8.7|) Ed Breakdown of masses to be included in analysis may be better suited in A.8.7 rather than 8.7

Relocate list of masses to be included currently listed after para 1 in 8.7 to A.8.7

UK C.2 C.2-12a Ed The h in equation C.2-12a should be squared and not multiplied by 2.

Square the h term and remove the multiplier.

UK Flowchart fig 5.1

Determine Responses box

Ed Reference to 10.3-10.5 instead of 10.5, and to fig 10.3.1



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UK A.7.3.3.3 Fig A.7.3-1 Te The variables shown on each axis of the chart are not defined in the document. For example on the Y axis does H refer to the significant or maximum wave height?.

Include these variables in the charts nomenclature

UK A.10.5.2.2.1 Fig A.10.5-1 (b)

Te No equation is presented for the calculation of Fin. This should be included as it is fundamentally different to the equation used for the SDOF method.

Include the relevant equation for Fin such that the user does not use the equation presented for the SDOF method by accident.

UK A.10.5.2.2.2 Para ‘2)’ Te This statement is inaccurate and misleading to the reader.

The word ‘peak’ should be changed to ‘trough’ and the reference to natural period should be changed to wave period. Alternatively the paragraph should be reworded to specify under which exact conditions the SDOF method may be un-conservative. This problem is also not exclusive to the SDOF method and therefore the text should be moved to a higher level in the document.

UK A.12.4.3 Table A.12.4-1

Te ‘lateral loading’ of members not qualified - wave/current loading (which may be lower than self weight loads per member) or structural point loads e.g. guide loads

Qualify ‘lateral loading’ e.g. does wave/current loading qualify (which may be lower than self weight loads per member) or is this intended to be structural point loads e.g. guide loads

iso phase 2 benchmarking...figure 8: iso predicted v-h envelope for the super gorilla - sand...

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