ISO TC 67 / SC 7 / WG 7 / Panel 10 - DNV GL · 2009. 10. 13. · Determine hull elevation (Clause 13.6) or as dictated by other considerations, if higher (Clause 5.4.5) Estimate leg

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ISO TC 67 / SC 7 / WG 7 / Panel 10

ISO 19905-1

PHASE 1 BENCHMARKING OF ISO 19905-1.9 - COMPLETENESS CHECK

Report No: L23332/NDC/YH

APPENDIX E- PHASE 2 PROPOSAL

02.10.2009 2 Re-named due to update of main report YH MJRH

14.04.2009 1 Separated from main report Updated for client comments YH MJRH/ RWPS

10.12.2008 O Initial Issue for Client Review YH MJRH/ RWPS

30 04.2008 Draft 1 Draft For Internal Review YH RWPS

Date Rev. Description Prepared by Authorised by

DRAFT ISO 19905-1

PHASE 1 BENCHMARKING OF ISO 19905-1.9

L23332/NDC/YH App E Rev 2 02/10/2009 Page 2

APPENDIX E

E PHASE 2 PROPOSAL

DRAFT ISO 19905-1



ISO TC 67 / SC 7 / WG 7 / Panel 10

ISO 19905-1

Phase 2 Benchmarking of ISO 19905-1 Proposed Scope of Work and Reporting Format

Contents

1 INTRODUCTION 4 2 SCOPE OF WORK PHASE 2 - COMPARISON TO SNAME 5-5A 6 3 APPROACH, REPORTING FORMATS & "STOP POINTS" (DRAFT) 12

3.1 GENERAL 12 3.2 ASSESSMENT SITUATIONS 12 3.3 RIG DATA 13 3.4 SITE DATA 16 3.5 METOCEAN DATA 16 3.6 MINIMUM HULL ELEVATION CHECK 17 3.7 GEOTECHNICAL AND GEOPHYSICAL DATA 17 3.8 LEG LENGTH RESERVE CHECK 18 3.9 LEG AND SPUDCAN BUOYANCY 19 3.10 HYDRODYNAMIC COEFFICIENTS 19 3.11 WIND ACTIONS 24 3.12 FE MODELS FOR LEG AND HULL 24

3.12.1 General 24 3.12.2 Mass model 24 3.12.3 Leg Inclination 24

3.13 ACTIONS 25 3.14 DYNAMIC MODELLING 25 3.15 ACTION SUMMARY 26 3.16 FOUNDATION INTEGRITY CHECK 28 3.17 LOWER GUIDE REACTIONS AND LEG INCLINATION 28 3.18 UTILISATION CHECKS OF LEG MEMBERS 30 3.19 UTILISATION CHECK OF HOLDING SYSTEM 31 3.20 UTILISATION CHECK OF SPUDCAN INCLUDING CONNECTION TO

THE LEG 32 3.21 SUMMARY OF THE ASSESSMENTS 32

DRAFT ISO 19905-1



1 INTRODUCTION 1.1 One of the deliverables required for the Phase 1 “Completeness Check” study was a

proposal for the layout or format of the Phase 2 “Comparison to SNAME 5-5A” study.

1.2 The purpose of the Phase 2 study is to undertake a complete run through the entire ISO 19905-1 standard 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 5-5A Rev 2 << Note to Committee: This is to be decided: basic Rev 2, Rev 2 with ND/OU updates, or to Rev 3 (draft dated zz) >> procedures. It is anticipated that there will be some differences between the results from the two documents since there have been some real changes made in ISO 19901-1, however it is not anticipated that these changes will cause major changes to the results.

1.3 Phase 2 will be initially be undertaken by a single consultant, largely to ensure that any gaps identified in Phase 1 have been plugged. After this, further consultants will be funded to run through a variety of cases to ensure that they:

• Do not find any additional roadblocks

• Come the same conclusions and numerical answers.

1.4 The intention is to select two jack up designs at specific locations and analyze them using SNAME 5-5A Rev 2 << Note to Committee: This is to be decided: basic Rev 2, Rev 2 with ND/OU updates, or to Rev 3 (draft dated zz) >> and then again using the same assumptions to the provisions ISO 19905-1.

1.5 Phase 2 will is to be a formal test of the documentation to ensure that it is useable by the public and will achieve acceptable answers.

1.6 An overall flow chart for the analysis is provided in Figure 1-1.

DRAFT ISO 19905-1



Figure 1-1 Overall flow char for the assessment

OK

Not OK

Obtain rig data and establish proposed Weights and C. of G.s (Clause 6.2) Obtain site and environmental data (Clauses 6.3 & 6.4)

Obtain geotechnical data (Clause 6.5)

Will “other aspects” limit suitability: - Hydrodynamics (Clause 7.3)

- Foundations (Clause 9) - Condition of unit (Clause 7.4)

Preventive measures available and will be adopted?

Determine hull elevation (Clause 13.6) or as dictated by other considerations, if higher (Clause 5.4.5) Estimate leg penetrations based on maximum preload (Section 9.3.2)

Determine responses, e.g. SDOF method (Clause 10.5)

Assess structure strength and overturning stability (Clauses 12 & 13.8)

If required, re-assess penetration (Clause 9.3.2) & leg length (Clauses 5.4.6 & 13.7)

Choose more detailed: - Response calculation (Clause 8.2.3) - Response calculation including foundation fixity (Clause 8.2.3 & Clause 8. 6.3)

If applicable, check horizontal deflections (Clause 13.9.2)

UNIT SUITABLE

Assess foundation (Clauses 9.3 & 13.9.1)

Yes

UNIT UNSUITABLE

No

Yes No

Is adequate leg length reserve available? (Clauses 5.4.6 & 13.7)

No

Choose to calculate required preload and re-assess penetration

and leg length reserve?

No

Comparable calculations according to this document exist and show acceptability? (Clause 5.2).

Establish hydrodynamic coefficients (Clause 7.3.2); wind loads (Clause 7.3.4) Prepare analysis models (Clause 8)

Yes

No

OK

UNIT UNSUITABLE

Not OK

Not OK

Not OK

Not OK

OK

OK

OK

Yes

Yes Yes

Not OK

Assess foundation (Clauses 9.3 &

13.9.1)

DRAFT ISO 19905-1



2 SCOPE OF WORK PHASE 2 - COMPARISON TO SNAME 5-5A

2.1 SCOPE OF PHASE 2 WORK 2.1.1 Phase 1 was completed mainly to check the process of the analysis: can one get

through the analysis without too many road blocks. The purpose of Phase 2 is to check the validity of the results of a complete ISO 19905-1 analysis. The steps will be very similar to those taken in Phase 1, but considerable care needs to be taken to ensure that there is numerical accuracy. Because the "answer" is so important to Phase 2, it will be important that the method is well established, and that the analysis can be completed with a minimum of unspecified choices having to be made.

2.1.2 Initially Phase 2 will be undertaken by a single consultant to ensure that all, or at least most, of the gaps found in Phase 1 had been plugged. However, after a successful analysis, it is anticipated that three other consultants will be funded to run through a variety of cases (see Table 2-1) to ensure that they:

• Do not find any additional roadblocks, and

• Come to the same conclusions/numerical answers

Table 2-1 Rig Cases and Consultants for Phase 2

Consultant Phase 2 Rigs assessed

A 1 & 2

B 1 & 3

C 2 & 4

D 3 & 4

E Results analysis

The results from the four analytical consultants will be presented by the consultants in individual reports. These will be collated, summarised and assessed by a fifth, independent consultant.

For each rig assessed, one consultant will be designated the "primary" consultant, e.g. as shown by the use of bold text in Table 2-1, although the final assignments will be determined by the Benchmarking Sub-Committee.

2.1.3 The process will be to take two jack-up designs at specific locations, and analyze them based on SNAME 5-5A. They would then be analyzed based on 19905-1, using the same assumption (e.g. fixity, pinned, etc.) to ensure that any differences in the solution are expected. It is known that certain areas of 19905-1 are different from SNAME 5-5A, so one would expect different answers from those clauses. However, large parts of the two documents have the same foundation, and should produce the same results.

2.1.4 The assessment should cover the calculations required to demonstrate the acceptability of the unit at the specified location. It is assumed that FE modelling will be used for the assessment but it is not anticipated that the hull strength itself will require verification.

DRAFT ISO 19905-1



2.1.5 Comparison with SNAME 5-5A checks will be based around analyses of the storm survival ULS loading condition, assuming an L1 exposure (i.e. permanently manned). The 50-year return period met-ocean option shall be adopted. It will not be necessary to undertake a seismic comparative analysis as the SNAME document provides little in the way of instruction on how this should be conducted, and benchmarking of the seismic provisions of ISO is to be undertaken as a separate exercise. .

2.1.6 The intent is that the Phase 2 work will be carried out more "mechanically" than Phase 1. Phase 1 was expected to require considerable thought and understanding to overcome the probably large number of errors and inconsistencies that would be found. However, Phase 2 needs to be a formal test of the document to ensure that it is useable by the public, and will achieve acceptable answers. Because Phase 2 will require regimented adherence to the document, albeit with considerable thought, it should be relatively simple to build on the embryo "Go-By" document developed in Phase 1 and flesh it out into a more complete template.

2.1.7 The steps taken in Phase 2 will match those from Phase 1. All key intermediate results need to be reported for both the SNAME analyses and the ISO analyses. "Stop Points" have been specified so that the output from a particular phase can be aligned either between SNAME and ISO or between different consultants in order to be able to see differences at the next stage. The analyses will also be run and reported without stop point adjustments in order to obtain a true numerical comparison of the final results.

2.1.8 Where there are differences between the consultants, these will generally be resolved by using the "primary" consultant's values unless there is technical justification for doing otherwise. It must be recognised that the focus should be on obtaining meaningful ISO results; the SNAME results are for comparison only and the consultants should not spend significant time reconciling the SNAME results with ISO or between themselves. << Note to Committee: This is a potential minefield when we have two consultants each undertaking an ISO and a SNAME analysis. The second consultant in each case will carry out his basic "own approach" analysis for ISO and for SNAME may end up undertaking "stop point" analyses for each too. Does the Committee want to go that far on the SNAME side? >>

2.1.9 If significant technical/interpretation queries arise during the course of the work, these are to be brought to the attentions of the Benchmarking Sub-Committee << or someone else? >> so that they can be resolved and the resolution shared with the other consultants at the earliest opportunity. The intent is not to stop the process, but to ensure that misunderstandings are minimised.

2.1.10 The Phase 2 report needs to address any interpretation problems, as for Phase 1. In addition, all results, including all intermediate results, need to be carefully reported, and the cause of differences identified where possible. It cannot be overstated that the numerical answers and conclusions from the Phase 2 analyses are of critical importance, so extreme care needs to be taken. Conversely, if there are areas within the standard that are easily open to misinterpretation, then these must be highlighted for clarification and correction.

2.1.11 It is possible that the main consultants may use a single independent geotechnical consultant to help with that aspect of the work. The intent would be to check the document, but not put undue burden on consultants who lack certain easily subcontracted skill sets. There would also be little point in each consultant

DRAFT ISO 19905-1



independently going to a single geotechnical company. However, it is important that geotechnical engineers from more than one consultant are involved in Phase 2, so that there is a greater probability that interpretation problems and ambiguities are identified. One of the consultants should be requested to undertake a critical review of not only the clauses he uses, but also the remaining geotechnical clauses, ideally using a junior geotechnical engineer.

2.1.12 In each case considered the same path through the document should be taken by the consultant pairs, in areas where this could have a significant impact e.g. approaches to dynamics & fixity. It will therefore be necessary for such matters to be agreed between the consultant pairs before the work is progressed, noting that it is anticipated that the most complex methods will not be applied in Phase 2. << Note to Committee: Does the Committee wish to compare the different methods? We suggest that, if this is the case, it is better that such comparisons be undertaken by a single consultant, otherwise the comparison may be obscured by modelling differences. >>.

2.1.13 The key steps that are required (these are essentially as per Phase 1, but with some re-ordering and updating) are shown below. Areas of potential divergence between consultants are highlighted.

1. Choose an independent leg jack-up and location/metocean condition that are likely to result in the unit being relatively close to its acceptance limits (only one water depth case needs to be considered, but it must be sufficiently deep for the unit to display a reasonably dynamic response). <<Note: The two consultants for each combination should, with the Committee, agree the rig/site combinations that they will consider. >>

2. Develop the required metocean assessment conditions from a standard metocean report. Determine the required minimum hull elevation to be the more conservative of the standard approach and that using the abnormal water level. Note: The two consultants should undertake independent interpretations of the data. However, the interpretation by the "primary" consultant should be adopted in the analyses undertaken by the second consultant. << Note to Committee: There should be no differences at this point, but if there are, we see no benefit in tracking their effects through the comparison. But, by having each consultant do this separately, we may reveal shortcomings in the ISO. >>.

3. Develop the foundation parameters from a suitable soils report for both a sand and clay soil condition. The committee is expecting that some clay locations selected will result in penetrations that would be considered deep (greater than 100 feet) and representative of GoMex conditions. << Note to Committee: 40 feet is too small to really exercise the SAGE updates >>. Note: Suitable clay soils reports can be provided.

4. Develop the rig loading conditions from the operating manual (preload, minimum and maximum storm survival condition, earthquake assessment condition, etc.). Note: The two consultants should undertake independent determinations of the loading conditions. However, the interpretation by the "primary" consultant should be adopted in the analyses undertaken by the second consultant. >> <<Note to Committee: There should be no differences at this point, but if there are, we see no benefit in tracking their effects through the comparison. But, by having each consultant do this separately, we may reveal shortcomings in the ISO. >>

DRAFT ISO 19905-1



5. Calculate the leg penetration in the two interpreted soils conditions, one sand, one clay. Note that it may be advantageous to check the completeness of some of the other penetration formulae through simple review with modifications of the used soil conditions (e.g. through generation of a simplified layered soils, etc.) - FIRST “STOP-POINT". <<Note to Committee: Should the ISO and SNAME penetrations differ markedly, what would the Committee like to be done? The Note is our suggestion. >> Note: Where possible, the two consultants should undertake independent determinations of the load-penetration behaviour. In addition to running with his own ISO interpretation the second consultant should also run using the ISO interpretation by the primary consultant. Develop spudcan fixity levels and the relevant soil springs. Note: The two consultants should undertake independent determinations of the fixity parameters (initial stiffness and capacity). In addition to running with his own ISO interpretation the second consultant should also run the analysis using the ISO interpretation by the first consultant. <<Note to Committee: Should the ISO and SNAME penetrations differ markedly, what would the Committee like done for the associated fixity? A pragmatic approach may be needed e.g. document the differences and continue with the different values. >>

7. Undertake the overall system geometry checks (leg length, etc.).

8. Calculate the hull wind area and leg hydrodynamic parameters.

9. Prepare a model that complies with the requirements of the standard, where possible based on an existing model of the unit. Note areas where revisions were required.

10. Calculate both a pinned natural period, and one incorporating spudcan fixity. Also determine sway stiffness to "unit" loading applied to the hull for both pinned and spudcan fixity cases. These results are to be compared between consultants. If there are significant differences, the modelling should be reviewed so that these can be understood and, if possible, reconciled. << Does the Committee want to do this? It means running in parallel not sequentially >>

11. Determine loading directions. These may be a subset of those that might normally be considered, but the same directions should be used for both ISO and SNAME analyse and by all consultants studying the rig/site combination.

12. Calculate the structural response based on the model incorporating fixity.

13. Summarise breakdown of loadings (wind, wave-current, inertia) and responses (hull sway, footing reactions and forces in legs just below lower guide) .- SECOND "STOP-POINT". Where there are significant differences between the results from the "same inputs analyses" obtained by the two consultants, the second consultant should update his own interpretation and/or run using the interpretation by the first consultant.

14. Assess the strength of the soils and determine level of additional penetration (if applicable).

15. Address the effects of any additional penetration.

DRAFT ISO 19905-1



16. Develop the (prismatic) chord and (tubular) bracing loads.

17. Undertake the tubular and prismatic member checks. It is anticipated that member classification for prismatic members would be checked rigorously for the specific chord shapes chosen.

18. Develop utilizations for the capacity of the holding system.

19. Develop utilizations for any remaining limit states set out in the standard.

2.2 DELIVERABLES FROM PHASE 2 2.2.1 Interim reporting of the key results will be required using the simple tabular format

shown in Section 3 of this Appendix.

2.2.2 When a "Stop Point" is reached the two consultants will share their intermediate results. If there are differences that cannot be readily reconciled, the values from the "primary" consultant will used by the other consultant unless there is technical justification for doing otherwise. In such cases, the other consultant should also provide results based on his original values (unless he decides they are no longer applicable).

2.2.3 After completion of the analyses a report should be issued that details the work undertaken in performing the analyses. The report needs to be detailed, well documented, and organized to assist the reader in following the process and logic. Any problems with the standard need to be described in the text and summarized within tables. Where options have been taken, either by choosing a permissible path within the standard, or through necessity to get through the analysis, then these need to be clearly stated. Specific items that need to be brought out in the report include:

• Executive Summary of results

• Inputs used at the start of the analysis (e.g. types of jack-up, metocean conditions, basic soil conditions, and other parameters normally available when undertaking a site specific jack-up assessment).

• Intermediate analysis results and comments (e.g. leg hydrodynamic properties, hull wind areas, loading conditions, air gap, leg penetrations, etc.).

• Full set of analysis results and any relevant comments on the results of the analyses.

• Detailed register of ALL questions that arose during the work. The register should contain, in tabular form, at least the following: the Question, Answer (if coming from within the ISO document), Resolution (if requiring additional information/interpretation from outside the document), Where document needs changing and, if possible/reasonable, suggested changes to the document to clarify the issue.

• List of ALL programs that were used in the analysis, reason for use, brief discussion of whether the program: follows ISO procedure, follows main ISO path or alternate route, reason for chosen analysis method with program, if the part of the document being simulated by the program is adequately defined. Note: as a general rule the use of in-house proprietary programs is discouraged since they do not "test" the document.

DRAFT ISO 19905-1



• Clauses where there was potential for confusion, but the intent of the standard was relatively clear. Reason for the confusion and, if possible, proposals for resolving the confusion.

• Clauses where assumptions had to be made in order to continue the analysis since the existing standard was either unclear or inconsistent. The report should state the assumptions that were actually made to continue analysis and, if possible, provide proposals for resolving the confusion.

• Clauses where there are errors or omissions that necessitate major assumptions to be made in order to continue the analysis. Need to include the cause of the error and possible corrective measures. In case of omissions, what assumptions were made and, if possible, propose additions to the document.

• Clause with contradictions. Need to include the cause of the contradiction, how issue was resolved during the analysis and, if possible, suggestions for rewording the clause to resolve the contradictions.

• Development of the "Go-By" document from Phase 1. <<Note to Committee: The Committee needs to decide how to carve this up between Consultants. >>

• One of the consultants will be requested to provide a Scope of Work and deliverables list/format for Phase 3 (if considered appropriate). This will be used by the benchmarking oversight committee to help develop the RFQ to solicit bids for phase 3 work. It should also help ensure that the phase 3 work is consistently undertaken and reported - which is imperative if the results are to be easily assessed.

DRAFT ISO 19905-1



3 APPROACH, REPORTING FORMATS & "STOP POINTS" (DRAFT)

3.1 GENERAL 3.1.1 As the overall results for the assessments depend on the accumulation of effects it is

desirable that the comparison should take place in stages with established cut off points (called “STOP-POINTS”) which will allow the best possible estimate to be made of how the two analysis methods perform. These stop points are described in detail in the following sections.

3.2 ASSESSMENT SITUATIONS 3.2.1 The Metocean and Geotechnical conditions at the selected location should be

reviewed and the necessary critical data for the location should be assessed as indicated in Table 3-1 for each of the sites under consideration.

Table 3-1 Assessment Situation of the Unit

Location Site Reference

Limit state ULS (Ultimate Limit States)

Exposure level L1 = S1 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 to be indicated

Spudcan Reaction point

(e.g. According to spudcan penetration as specified in Clause A.8.6.2)

Centre of gravity (location & tolerances)…

Specific Hull elevation wrt LAT

Others

DRAFT ISO 19905-1



3.3 RIG DATA 3.3.1 Key rig data should be tabulated using Table 3-2.

Table 3-2 Assembled Rig Data

DRAFT ISO 19905-1



Rig Type ……………..

Drawings & specifications (List Refs.) …………….

Operation manual (List Refs.) …………….

General

1. Indicate clearly which units are being used in each case, i.e. tonne, N, m etc.

2. Provides sketches showing axes systems for the different parts of the structure.

Rack-chock (per chock/pair)

Kvertical = ……… Kradial = ………

Ktangental = ………

Upper-guide

Kradial = ……….. Radial Gap = ………) Ktangential = ……….. Tangential Gap = ………)

(if stiffnesses or gaps are applicable in other axes include diagrams etc.)

Lower-guide

Kradial = ……….. Radial Gap = ………) Ktangential = ……….. Tangential Gap = ………)

(if stiffnesses or gaps are applicable in other axes include diagrams etc.)

Leg-hull connection details & stiffness

Pinion K = …… (vertical/ pressure angle)

(Backlash =…...) (indicate with sketches axis used for springs and gaps)

Principle Dimensions

Hull Length x Width x Height …..m x …..m x ……m (from ………)

Leg Length including spudcan ………….m

Weight & Centre of gravity

Hull lightship ………. tonnes

Assessed Maximum Variable loadAssessed Minimum Variable load

……………. tonnes


Assessed Maximum Hull weightAssessed Minimum Hull weight


……………. Tonnes

CoG of Assessed hull weightLCG=……….m, tolerance = TCG=………m, tolerance = VCG=……….m, tolerance =

Weight of each Leg including spudcan and centres of gravity

(confirm whether spudcan is dry or flooded; define axes system used for centres

of gravity)

……….. Tonnes

LCG=……..m TCG=………m

VCG=…………m

Preload Capacity (jacking reaction) per leg ……….. tonnes

Spudcan dimensions

Height of spudcan ……….m

Maximum bearing area …………. M2

Height of max bearing area above tip ………….m

Spudcan Dry Weight

DRAFT ISO 19905-1



Spudcan flooded buoyant weight

Relevant modifications N/A

DRAFT ISO 19905-1



3.4 SITE DATA 3.4.1 Key characteristics of the Site are shown in Table 3-3.

Table 3-3 Assembled Site Data

Site Reference

Site coordinates (Lat. and Long. or eastings and northings (in which case specify origin and system used)

……………N, ……………E ……………Easting,………………..Northing

Seabed type (Sand or Clay) …………….

Water depth (LAT) ……….m

3.5 METOCEAN DATA 3.5.1 The Metocean data assembled for a site should be provided using a table similar to

that shown in Table 3-4.

Table 3-4 Assembled Metocean Data[1]

Water depth (LAT) (m) …………..

Water depth (MWL) (m) ………….

Data type 50-year return individual extreme[2]

Mean high water spring tide (MHWS) (m) …………..

Storm surge (m) ………….

Significant wave height (m) …………..

Spectral peak period (sec) ……………

Spectrum (given / used) ………../…………

Peakedness parameter (given / used) ………../…………

Maximum wave height (m) …………….

Associated wave period (sec) ……………

Abnormal wave crest (m) ……………

Top surface ………

25% water depth ……….

50% water depth …………

75% water depth ………..

Current velocity profile (m/sec)

1m above seabed …………

1 minute Wind speed (m/sec) …………….

Other data Marine growth = ……….mm

DRAFT ISO 19905-1



3.6 MINIMUM HULL ELEVATION CHECK 3.6.1 Hull elevation data may be provided as in Table 3-5,

Table 3-5 Hull Elevation Check

Site…………

Mean high water spring tide (MHWS) (m) ………..

Storm surge (m) ……….

Maximum wave crest height (m) …………

Extreme still water level (SWL) (m) = …………

Required Margin (m)

Other allowances (m)

Minimum required hull elevation (m) = ……

Specified hull elevation (m) = ………

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

3.7 GEOTECHNICAL AND GEOPHYSICAL DATA 3.7.1 The foundation parameters obtained for the locations should be listed in a manner

similar to that in Table 3-6.

3.7.2 Due to differences in the geotechnical methodologies adopted by the ISO and SNAME documents there may be differences in the results obtained for given spudcan and preload data. It is therefore proposed that the results from these analyses will form the first STOP-POINT (see Section 2.1 Scope 5) for the study and that the analysis should then continue using the foundation penetration and fixity values produced by the ISO calculation method.

DRAFT ISO 19905-1



Table 3-6 Assembled Foundation Data

Site 1

Soil type description ……..

Layer 1 - Seabed to x m

Top: γ' = ; Cu = ∅= Bottom γ' = ; Cu = ∅=

Layer 2 - x m y m


Layer 3 - y m z m


etc…

Spudcan penetration (m) ………

Vertical capacity, VLO (kN/t) ………

Horizontal capacity, HLO (kN/t) ………

Moment capacity, MLO (kN-m /t-m) ………

Vertical stiffness, K1 (kN/m / t/m) ……….

Horizontal stiffness, K2 (kN/m / t/m) …………

Rotational stiffness, K3 (kN/m / t/m) …………

Distance of effective penetration point below sea floor (m)

3.8 LEG LENGTH RESERVE CHECK Table 3-7 Leg Length Reserve Check

Site Reference

Keel to top of Upper Guide (m) ……………..

Keel above sea level LAT (m) ………..

Water depth LAT (m) ………..

Spudcan penetration (m) ….……….

Total length used (m): ……………..

Leg length (m) ………..

Leg length reserve (m): ….………

DRAFT ISO 19905-1



3.9 LEG AND SPUDCAN BUOYANCY 3.9.1 The leg and spudcan buoyancies of the rig should be reported and listed for reference

such as in Table 3-8.

Table 3-8 Leg & Spudcan Buoyancy

Site Ref

Water depth (m) ……………

Spudcan height (m) ……………

Spudcan penetration (m) ……..………..

Single leg buoyancy (without spudcan) (tonnes)

……….……….

Single leg buoyancy (without spudcan) VCG (m)

……….………

Spudcan submerged buoyancy (tonnes)

…………..

Height of spudcan buoyancu VCG above spudcan tip (m)

……………

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. The values adopted for the analysis should be tabulated such as in Table 3-9.

Table 3-9 Hydrodynamic Surface Condition Levels

Site Ref

Water depth (m)

Mean high water spring tide (MHWS) (m)

Mean water level (MWL) (m) =

MWL + 2m =

Spudcan penetration beneath seafloor (m)

MWL above spudcan tip (m) = ……. + penetration =

Table 3-10 Hydrodynamic Leg Sections for selected Site

DRAFT ISO 19905-1



Section Bay numbers

Top of section above can tip (m) Section summary

1 x - y

2 z - a

3 ..

DRAFT ISO 19905-1



Table 3-11 Member details for Hydrodynamics calculations (to be repeated for each leg section)

Input (Section x)

Chord Horizontal Diagonal Internal Other

Length (m)

Diameter (m)

Angle to horizontal

3.10.2 Hydrodynamic coefficients for tubulars used in the analysis (see Table 3-12).

Table 3-12 Base hydrodynamic coefficients for Tubulars

Surface condition CDi CMi

Smooth (Above MWL + 2m)

Rough (Below MWL + 2m)

3.10.3 The selected marine growth thickness should be reported.

3.10.4 Chord hydrodynamic coefficients should be reported for all sections and a range of flow directions using Table 3-13.

DRAFT ISO 19905-1



Table 3-13 Chord hydrodynamic coefficients

Smooth Rough

Section

Flow Direction (sketch

axis system) CD CM De CD CM De

Added mass /unit

chord length

0

30

60

90

120

150

1

180

0

30

60

90

120

150

2

180

0

30

60

90

120

150

3

180

etc

DRAFT ISO 19905-1



3.10.5 Where an equivalent hydrodynamic model is used the equivalent hydrodynamic and current blockage coefficients should be reported for all sections and a range of flow directions.

3.10.6 If a detailed model is used, these data should be reported as far as is possible using Table 3-14.

Table 3-14 Equivalent leg hydrodynamic coefficients

Smooth Rough

Section

Flow Direction (sketch

axis system) CD CM De Cb CD CM De Cb

Added mass

/unit leg length

0

30

60

90

120

150

1

180

0

30

60

90

120

150

2

180

0

30

60

90

120

150

3

180

etc

DRAFT ISO 19905-1



3.11 WIND ACTIONS 3.11.1 The total effective wind area and related vertical centre of effort should be reported

using Table 3-15. The origin for the vertical centre of effort should be described.

Table 3-15 Wind Areas and Vertical Centre of Effort

Hull Legs Total

0

30

60

90

120

150

180

3.12 FE MODELS FOR LEG AND HULL

3.12.1 General 3.12.1.1 Please summarise modelling methodology for legs and spudcans, hull and leg-hull

connection (equivalent / detailed / etc.).

3.12.1.2 Diagram(s) of the model(s) should be presented, including the leg-hull connection.

3.12.2 Mass model 3.12.2.1 The mass model used to reflect the mass distribution of the jack-up should be

summarized.

3.12.3 Leg Inclination 3.12.3.1 Please describe the approach used to include leg inclination effects in the assessment

of the strength of the upper part of the leg and what leg inclination offset was used.

DRAFT ISO 19905-1



3.13 ACTIONS 3.13.1 Please summarise the direct and indirect actions that have been considered, and how

they have been modelled using Table 3-16.

Table 3-16 Summary of actions considered

Action Modelling Details

a) Functional actions due to fixed and variable loads

b) Hull sagging

c) Wind actions

d) Wave and current actions

e) Inertia actions

f) Large displacement effects

g) Conductor actions

h) Other applicable actions

3.14 DYNAMIC MODELLING 3.14.1 Please describe the way in which damping has been determined (with break-down by

source) and applied in the dynamic analyses.

3.14.2 Please describe the approach taken to determine the dynamic response, including, where applicable, the approach used to determine "qualified" storm histories, simulation length, and key statistics.

3.14.3 Please summarise the Natural Periods and dynamic amplification factors using either a single degree of freedom analysis (DAFS) or stochastic analyses (DAFR). For the Phase 2 benchmarking it is assumed that a stochastic analysis will be selected, in which a statistical method is used to determine the MPME of the dynamic response using Table 3-17.

DRAFT ISO 19905-1



Table 3-17 Natural Periods & DAF's

Hull weight =

Heading TN BS DAFS / DAFR OTM DAFS / DAFR

0

30

60

90

120

150

180

Yaw n/a n/a

The Natural period and the DAF's are based on a linear / non-linear model. (Repeat Table as necessary)

3.15 ACTION SUMMARY 3.15.1 The factored actions used in/resulting from the Extreme Storm analysis should be

reported as in Table 3-18. Please describe below the approach taken in determining and applying the inertial loadset and take this as the second STOP-POINT (see Section 2.1 Scope 13).

Table 3-18 Factored Base Shear and OTM

DRAFT ISO 19905-1



Site Ref: Units: Storm Direction

(sketch axis system)

º º º º º º

Base Shear:

Wind

Wave-Current

Inertial

Total BS

OTM::

Wind

Wave-Current

Inertial

Total OTM

Reference elevation for OTM, if other than pin-point = wrt

DRAFT ISO 19905-1



3.16 FOUNDATION INTEGRITY CHECK 3.16.1 The utilisations of the foundation capacity should be documented and reported in the

table below. If soil loading is such that additional penetration is required to provide a foundation capacity adequate for the computed reactions then this should be documented and reported. It is recommended to take this and HULL SWAY as the second STOP-POINT (see Section 2.1 Scope 13).

Table 3-19 Footing Reactions from the Global Responses (Site xx; Units: yy)

Site Direct Leg Axial Shear Preload UC

Bearing UC

Sliding UC

bow

port 0º

stbd

bow

port ---

stbd

bow

port

Hull Weight =

---

stbd

bow

port 0º

stbd

bow

port ---

stbd

bow

port

Hull Weight =t

---

stbd

3.17 LOWER GUIDE REACTIONS AND LEG INCLINATION 3.17.1 Where possible, the loads in the leg cross-section just below the level of the lower

guide should be reported using the format shown in Table 3-20. All important load directions should be included. It is recommended to take this as the second STOP-POINT (see Section 2.1 Scope 13).

DRAFT ISO 19905-1



Table 3-20 Loads in leg just below the level of the lower guide

Inclination moment Site …. Direct Leg Axial

(units) Y-Shear (units)

Z-Shear (units)

Torsion (units)

[1]Y-Bending (units)

[1]Z-Bending (units) Y Z

bow

port 0º

stbd

bow

port --

stbd

bow

port

Hull Weight =

--

stbd

bow

port 0º

stbd

bow

port --

stbd

bow

port

Hull Weight =

--

stbd [1] The additional leg moment due to leg inclination resulting from leg-hull clearances and hull

inclination is/is not included in the values in theses columns.

3.17.2 Please summarise the additional leg moments due to leg inclination in two right hand columns of the table above.

DRAFT ISO 19905-1



3.18 UTILISATION CHECKS OF LEG MEMBERS 3.18.1 The critical member utilisation checks should be summarised in Table 3-21 for, at

least, the more critical loading directions.

Table 3-21 Member checks

Utilisations

Site …. Leg

Member Axial (units)

Y-Shear (units)

Z-Shear (units)

Max

Shear force(u

nits)

Max Section torqu(un

its)e Shear Tors-

ion Comb-

ined

Chord

H brace Bow

D brace

Chord

H brace

Port D brace

Chord

H brace

Hull Weight = Heading = º

Stbd D brace

Chord

H brace Bow

D brace

Chord

H brace

Port D brace

Chord

H brace


Stbd D brace

Chord

H brace Bow

D brace

Chord

H brace

Port D brace

Chord

H brace


Stbd D brace

(Extend table as required)

Please summarise the member lengths and effective length factors used for each member type:

DRAFT ISO 19905-1



3.19 UTILISATION CHECK OF HOLDING SYSTEM 3.19.1 The critical holding system utilisation checks should be summarised in Table 3-22

for, at least, the more critical loading directions.

Table 3-22 Maximum Utilisations of the Holding System

Site …. Leg Load (units) Allowable Load (units) Utilisation

Bow

Port


Stbd

Bow

Port


Stbd

Bow

Port


Stbd

DRAFT ISO 19905-1



3.20 UTILISATION CHECK OF SPUDCAN INCLUDING CONNECTION TO THE LEG

3.20.1 If required this aspect of leg strength is critical is should be documented and results reported (use Table 3-21).

3.21 SUMMARY OF THE ASSESSMENTS 3.21.1 The maximum utilisations obtained in the assessments should be summarised shown

in Table 3-23.

Table 3-23 Summary of Assessment Results

ISO SNAME

Criteria 50-year, individual extremes, ULS

Hull elevation (units) Air gap = > Minimum clearance = ----

Leg length reserve (units)

Spudcan penetration (units)

Utilisations UC Heading UC Heading

Maximum Preload Utilisation

Maximum Bearing Utilisation

Additional penetration (units)

Maximum Sliding Utilisation

Maximum Hull Sway

Maximum Chord Utilisation

Maximum Brace Utilisation

Maximum Chock Utilisation

Max Overturning Utilisation

Hull Sway (units)

Documents

ISO TC 67 / SC 7 / WG 7 / Panel 10 - DNV GL · 2009. 10. 13. · Determine hull elevation (Clause 13.6) or as dictated by other considerations, if higher (Clause 5.4.5) Estimate leg