ISO 19905-1:2012

Petroleum and natural gas industries — Site-specific assessment of mobile offshore units — Part 1: Jack-ups

ISO 19905-1:2012 specifies requirements and guidance for the site-specific assessment of independent leg jack‑up units for use in the petroleum and natural gas industries. It addresses manned non-evacuated, manned evacuated and unmanned jack‑ups; the installed phase at a specific site. To ensure acceptable reliability, the provisions of ISO 19905-1:2012 form an integrated approach, which is used in its entirety for the site-specific assessment of a jack‑up. ISO 19905-1:2012 does not apply specifically to mobile offshore drilling units operating in regions subject to sea ice and icebergs. When assessing a jack-up operating in such areas, it is intended that the assessor supplement the provisions of ISO 19905-1:2012 with the provisions relating to ice actions and procedures for ice management contained in ISO 19906. ISO 19905-1:2012 does not address design, transportation to and from site, or installation and removal from site. However, it is advisable that the assumptions used in the assessment be checked against the as-installed configuration. To ensure that the design of the jack‑up is sound and the structure is adequately maintained, ISO 19905-1:2012 is applicable only to independent leg jack‑ups that either: hold a valid classification society certification from a recognized classification society (RCS) throughout the duration of the operation at the specific site subject to assessment, or have been verified by an independent competent body to be structurally fit for purpose for elevated situations and are subject to periodic inspection, both to the standards of an RCS. Jack‑ups that do not comply with this requirement are assessed according to the provisions of ISO 19902, supplemented by methodologies from ISO 19905-1:2012, where applicable.

Industries du pétrole et du gaz naturel — Évaluation spécifique au site d'unités mobiles en mer — Partie 1: Plates-formes auto-élévatrices

General Information

• Status: Withdrawn
• Publication Date: 24-Jul-2012
• Withdrawal Date: 24-Jul-2012
• ICS: 75.180.10 - Exploratory, drilling and extraction equipment
• Technical Committee: ISO/TC 67/SC 7 - Offshore structures
• Drafting Committee: ISO/TC 67/SC 7/WG 7 - Site specific assessment of mobile offshore units (MOUS)
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 15-Jan-2016

Relations

• Revised: ISO 19905-1:2016 - Petroleum and natural gas industries — Site-specific assessment of mobile offshore units — Part 1: Jack-ups
• Effective Date: 04-Nov-2015
• Consolidates: ISO 8434-5:1995 - Metallic tube connections for fluid power and general use — Part 5: Test methods for threaded hydraulic fluid power connections
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 19905-1
First edition
2012-08-01

Petroleum and natural gas industries —
Site-specific assessment of mobile
offshore units —
Part 1:
Jack-ups
Industries du pétrole et du gaz naturel — Évaluation spécifique au site
d'unités mobiles en mer —
Partie 1: Plates-formes auto-élévatrices




Reference number
ISO 19905-1:2012(E)
©
ISO 2012

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ISO 19905-1:2012(E)

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©  ISO 2012
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Published in Switzerland
ii © ISO 2012 – All rights reserved

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ISO 19905-1:2012(E)
Contents Page
Foreword . v
Introduction . vii
1  Scope . 1
2  Normative references . 2
3  Terms and definitions . 2
4  Symbols and abbreviated terms . 13
4.1  Symbols . 13
4.2  Abbreviated terms . 14
5  Overall considerations . 15
5.1  General . 15
5.2  Assessment approach . 16
5.3  Selection of limit states . 18
5.4  Determination of assessment situations . 18
5.5  Exposure levels . 20
5.6  Analytical tools . 23
6  Data to assemble for each site . 24
6.1  Applicability . 24
6.2  Jack-up data . 24
6.3  Site and operational data . 24
6.4  Metocean data . 24
6.5  Geophysical and geotechnical data . 25
6.6  Earthquake data . 26
7  Actions. 26
7.1  Applicability . 26
7.2  General . 26
7.3  Metocean actions . 27
7.4  Functional actions . 28
7.5  Displacement dependent effects . 28
7.6  Dynamic effects . 28
7.7  Earthquakes . 28
7.8  Other actions . 28
8  Structural modelling . 28
8.1  Applicability . 28
8.2  Overall considerations . 28
8.3  Modelling the leg . 29
8.4  Modelling the hull . 30
8.5  Modelling the leg-to-hull connection . 30
8.6  Modelling the spudcan and foundation . 31
8.7  Mass modelling . 32
8.8  Application of actions . 32
9  Foundations . 35
9.1  Applicability . 35
9.2  General . 35
9.3  Geotechnical analysis of independent leg foundations . 36
9.4  Other considerations . 39
10  Structural response . 41
10.1  Applicability . 41
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ISO 19905-1:2012(E)
10.2  General considerations .41
10.3  Types of analyses and associated methods .41
10.4  Common parameters .42
10.5  Storm analysis .44
10.6  Fatigue analysis .47
10.7  Earthquake analysis .47
10.8  Accidental situations .47
10.9  Alternative analysis methods .48
11  Long-term applications .48
11.1  Applicability .48
11.2  Assessment data .48
11.3  Special requirements .49
11.4  Survey requirements .50
12  Structural strength.50
12.1  Applicability .50
12.2  Classification of member cross-sections .51
12.3  Section properties of non-circular prismatic members .52
12.4  Effects of axial force on bending moment .53
12.5  Strength of tubular members .53
12.6  Strength of non-circular prismatic members .53
12.7  Assessment of joints .53
13  Acceptance criteria .54
13.1  Applicability .54
13.2  General formulation of the assessment check .55
13.3  Leg strength assessment .55
13.4  Spudcan strength assessment .56
13.5  Holding system strength assessment .56
13.6  Hull elevation assessment .56
13.7  Leg length reserve assessment .56
13.8  Overturning stability assessment .57
13.9  Foundation integrity assessment .57
13.10  Interaction with adjacent infrastructure .58
13.11  Temperatures .59
Annex A (informative) Additional information and guidance .60
Annex B (normative) Summary of partial action and partial resistance factors . 238
Annex C (informative) Additional information on structural modelling and response analysis . 240
Annex D (informative) Foundations — Recommendations for the acquisition of site-specific
geotechnical data. 250
Annex E (informative) Foundations — Additional information and alternative approaches . 256
Annex F (informative) Informative annex on Clause A.12 — Structural strength . 269
Annex G (informative) Contents list for typical site-specific assessment report . 283
Annex H (informative) Regional information . 290
Bibliography . 299

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ISO 19905-1:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 19905-1 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 7, Offshore structures.
ISO 19905 consists of the following parts, under the general title Petroleum and natural gas industries — Site-
specific assessment of mobile offshore units:
 Part 1: Jack-ups
 Part 2: Jack-ups commentary and detailed sample calculation [Technical Report]
The following part is under preparation:
 Part 3, dealing with the site-specific assessment of mobile floating units.
ISO 19905 is one of a series of International Standards for offshore structures. The full series consists of the
following International Standards:
 ISO 19900, Petroleum and natural gas industries — General requirements for offshore structures
 ISO 19901-1, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 1: Metocean design and operating considerations
 ISO 19901-2, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 2: Seismic design procedures and criteria
 ISO 19901-3, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 3: Topsides structure
 ISO 19901-4, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 4: Geotechnical and foundation design considerations
 ISO 19901-5, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 5: Weight control during engineering and construction
 ISO 19901-6, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 6: Marine operations
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ISO 19905-1:2012(E)
 ISO 19901-7, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 7: Stationkeeping systems for floating offshore structures and mobile offshore units
1)
 ISO 19901-8 , Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 8: Marine soils investigations
 ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures
 ISO 19903, Petroleum and natural gas industries — Fixed concrete offshore structures
 ISO 19904-1, Petroleum and natural gas industries — Floating offshore structures — Part 1: Monohulls,
semi-submersibles and spars
 ISO 19905-1, Petroleum and natural gas industries — Site-specific assessment of mobile offshore
units — Part 1: Jack-ups
 ISO/TR 19905-2, Petroleum and natural gas industries — Site-specific assessment of mobile offshore
units — Part 2: Jack-ups commentary and detailed sample calculation
2 )
, Petroleum and natural gas industries — Site-specific assessment of mobile offshore
 ISO 19905-3
units — Part 3: Floating units
 ISO 19906, Petroleum and natural gas industries — Arctic offshore structures


1) Under preparation. It is also expected that there will be further parts of ISO 19901.
2) Under preparation.
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ISO 19905-1:2012(E)
Introduction
The series of International Standards applicable to types of offshore structure, ISO 19900 to ISO 19906,
addresses design requirements and assessments for all offshore structures used by the petroleum and natural
gas industries worldwide. Through their application, the intention is to achieve reliability levels appropriate for
manned and unmanned offshore structures, whatever the type of structure and the nature or combination of
the materials used.
It is important to recognize that structural integrity is an overall concept comprising models for describing
actions, structural analyses, design or assessment rules, safety elements, workmanship, quality control
procedures and national requirements, all of which are mutually dependent. The modification of one aspect of
design or assessment in isolation can disturb the balance of reliability inherent in the overall concept or
structural system. The implications involved in modifications, therefore, need to be considered in relation to
the overall reliability of offshore structural systems.
The series of International Standards applicable to the various types of offshore structure is intended to
provide a wide latitude in the choice of structural configurations, materials and techniques, without hindering
innovation. Sound engineering judgement is therefore necessary in the use of these International Standards.
[7]
This part of ISO 19905, which has been developed from SNAME Technical & Research Bulletin 5-5A , states
the general principles and basic requirements for the site-specific assessment of mobile jack-ups; it is
intended to be used for assessment and not for design.
NOTE For the exposure level 1(L1) assessment and, where appropriate, the exposure level 2 (L2) assessment prior
to evacuation being effected, this part of ISO 19905 requires the use of 50 year independent or 100 year joint probability
metocean extremes, together with associated partial action factors. It is based on extensive benchmarking and best
practice in the international community.
Site-specific assessment is normally carried out when an existing jack-up unit is to be installed at a specific
site. The assessment is not intended to provide a full evaluation of the jack-up; it assumes that aspects not
addressed herein have been addressed using other practices and standards at the design stage. In some
instances, the original design of all or part of the structure could be in accordance with other standards in the
ISO 19900 series, and in some cases, different practices or standards could have been applied.
The purpose of the site assessment is to demonstrate the adequacy of the jack-up and its foundations for the
assessment situations and defined limit states, taking into account the consequences of failure. It is important
that the results of a site-specific assessment be appropriately recorded and communicated to those persons
required to know or act on the conclusions and recommendations. Alternative approaches to the site-specific
assessment can be used, provided that they have been shown to give a level of structural reliability equivalent,
or superior, to that implicit in this part of ISO 19905.
Annex A provides background to and guidance on the use of this part of ISO 19905. The clause numbering in
Annex A is the same as in the normative text in order to facilitate cross-referencing. ISO/TR 19905-2 provides
additional background to some clauses and a detailed sample 'go-by' calculation.
Annex B summarizes the partial factors. Supplementary information is presented in Annexes C to H.
To meet certain needs of industry for linking software to specific elements in this part of ISO 19905, a special
numbering system has been permitted for figures, tables, equations and bibliographic references.
In International Standards, the following verbal forms are used:
 “shall” and “shall not” are used to indicate requirements strictly to be followed in order to conform to the
document and from which no deviation is permitted;
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ISO 19905-1:2012(E)
 “should” and “should not” are used to indicate that, among several possibilities, one is recommended as
particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred
but not necessarily required, or that (in the negative form) a certain possibility or course of action is
deprecated but not prohibited;
 “may” is used to indicate a course of action permissible within the limits of the document;
 “can” and “cannot” are used for statements of possibility and capability, whether material, physical or
causal.

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INTERNATIONAL STANDARD ISO 19905-1:2012(E)

Petroleum and natural gas industries — Site-specific
assessment of mobile offshore units —
Part 1:
Jack-ups
1 Scope
This part of ISO 19905 specifies requirements and guidance for the site-specific assessment of independent
leg jack-up units for use in the petroleum and natural gas industries. It addresses
a) manned non-evacuated, manned evacuated and unmanned jack-ups;
b) the installed phase at a specific site.
To ensure acceptable reliability, the provisions of this part of ISO 19905 form an integrated approach, which is
used in its entirety for the site-specific assessment of a jack-up.
This part of ISO 19905 does not apply specifically to mobile offshore drilling units operating in regions subject
to sea ice and icebergs. When assessing a jack-up operating in such areas, it is intended that the assessor
supplement the provisions of this part of ISO 19905 with the provisions relating to ice actions and procedures
for ice management contained in ISO 19906.
This part of ISO 19905 does not address design, transportation to and from site, or installation and removal
from site. However, it is advisable that the assumptions used in the assessment be checked against the
as-installed configuration.
To ensure that the design of the jack-up is sound and the structure is adequately maintained, this part of
ISO 19905 is applicable only to independent leg jack-ups that either
 hold a valid classification society certification from a recognized classification society (RCS) throughout
the duration of the operation at the specific site subject to assessment; or
 have been verified by an independent competent body to be structurally fit for purpose for elevated
situations and are subject to periodic inspection, both to the standards of an RCS.
NOTE 1 An RCS is an International Association of Classification Societies (IACS) member body, meeting the RCS
definition given in 3.52.
Jack-ups that do not comply with this requirement are assessed according to the provisions of ISO 19902,
supplemented by methodologies from this part of ISO 19905, where applicable.
NOTE 2 Future revisions of this part of ISO 19905 can be expanded to cover mat-supported jack-ups.
NOTE 3 Well conductors are a safety-critical element for jack-up operations. However, the integrity of well conductors
is not part of the site-specific assessment process for jack-ups and is, therefore, not addressed in this part of ISO 19905.
Annex A provides references to other publications addressing this topic.
NOTE 4 RCS rules and the IMO MODU code provide guidance for the design of jack-ups.
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ISO 19905-1:2012(E)
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 19900, Petroleum and natural gas industries — General requirements for offshore structures
ISO 19901-1, Petroleum and natural gas industries — Specific requirements for offshore structures — Part 1:
Metocean design and operating conditions
ISO 19901-2, Petroleum and natural gas industries — Specific requirements for offshore structures — Part 2:
Seismic design procedures and criteria
ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 19900, ISO 19901-1, ISO 19901-2
3)
and ISO 19902, and the following apply.
3.1
abnormal wave crest
3 4
wave crest with probability of typically 10 to 10 per annum
3.2
accidental situation
exceptional situation of the structure
EXAMPLE Impact; fire; explosion; local failure; loss of intended differential pressure (e.g. buoyancy).
3.3
action
external load applied to the structure (direct action) or an imposed deformation or acceleration (indirect action)
EXAMPLE An imposed deformation can be caused by fabrication tolerances, settlement, temperature change or
moisture variation.
NOTE An earthquake typically generates imposed accelerations.
[ISO 19900:2002, definition 2.1]
3.4
assessment
site-specific assessment
evaluation of the stability and structural integrity of a jack-up and, where applicable, its seabed restraint or
support against the actions determined in accordance with the requirements of this part of ISO 19905
NOTE An assessment can be limited to an evaluation of the components or members of the structure which, when
removed or damaged, could cause failure of the whole structure, or a significant part of it.
3.5
assessment situation
jack-up configuration together with the environmental loading to be assessed
NOTE 1 For discussion on configuration, see 5.4.1.
NOTE 2 The assessment situations are checked against the acceptance criteria of this part of ISO 19905 to
demonstrate that the relevant limit states are not exceeded.

3) Other terms and definitions relevant for the use of this part of ISO 19905 are also found in ISO 19901-4 and
ISO 19906.
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ISO 19905-1:2012(E)
3.6
assessor
entity performing the site-specific assessment
3.7
backfill
submerged weight of all of the soil that can be present on top of the spudcan
NOTE Backfilling can occur during or after preloading. W refers to the submerged weight of the backfilling that
BF,o
occurs up to achieving the preload reaction. W refers to the submerged weight of
...