EN ISO 19900:2019

Petroleum and natural gas industries - General requirements for offshore structures (ISO 19900:2019)

This document specifies general requirements and recommendations for the design and assessment of bottom-founded (fixed) and buoyant (floating) offshore structures.
This document is applicable for all phases of the life of the structure, including:
—         successive stages of construction (i.e. fabrication, transportation, and installation),
—         service in-place, both during design life and during any life extensions, and
—         decommissioning, and removal.
This document contains general requirements and recommendations for both the design of new build structures and for the structural integrity management and assessment of existing structures.
This document does not apply to subsea and riser systems or pipeline systems.

Erdöl- und Erdgasindustrie - Allgemeine Anforderungen an Offshore-Bauwerke (ISO 19900:2019)

Industries du pétrole et du gaz naturel - Exigences générales relatives aux structures en mer (ISO 19900:2019)

Le présent document spécifie les exigences générales et recommandations régissant la conception et l'évaluation des structures en mer prenant appui sur le fond marin (fixes) et des structures en mer flottantes.
Le présent document s'applique à toutes les phases du cycle de vie de la structure, y compris:
—          les étapes successives de construction (c'est-à-dire la fabrication, le transport et l'installation);
—          l'exploitation, à la fois pendant la durée de vie de conception et pendant toute prolongation de la durée de vie; et
—          l'abandon et l'enlèvement.
Le présent document contient des exigences générales et recommandations à la fois pour la conception de nouvelles structures et pour la gestion et l'évaluation de l'intégrité structurelle des structures existantes.
Le présent document ne s'applique pas aux systèmes sous-marins de tubes conducteurs ou de conduites.

Industrija za predelavo nafte in zemeljskega plina - Splošne zahteve za vrtalne ploščadi (ISO 19900:2019)

Ta dokument določa splošne zahteve in priporočila za načrtovanje ter ocenjevanje na dno pritrjenih (fiksnih) in plovnih (plavajočih) vrtalnih ploščadi.
Ta dokument se uporablja za vse stopnje življenjskega cikla ploščadi in vključuje:
– zaporedne stopnje gradnje (npr. izdelava, prevoz in namestitev),
– delovanje na mestu uporabe tako med predvideno življenjsko dobo kot tudi pri podaljšanju življenjske dobe ter
– prenehanje uporabe in odstranitev.
Ta dokument vključuje splošne zahteve in priporočila za načrtovanje novozgrajenih ploščadi ter za upravljanje in ocenjevanje strukturne celovitosti obstoječih ploščadi.
Ta dokument se ne uporablja za podvodne in dvižne sisteme ali cevovode.

General Information

• Status: Published
• Publication Date: 09-Jul-2019
• Withdrawal Date: 30-Jan-2020
• ICS: 75.180.10 - Exploratory, drilling and extraction equipment
• Technical Committee: CEN/TC 12 - Materials, equipment and offshore structures for petroleum and natural gas industries
• Drafting Committee: CEN/TC 12 - Materials, equipment and offshore structures for petroleum and natural gas industries
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 10-Jul-2019
• Completion Date: 10-Jul-2019
• Ref Project: SIST EN ISO 19900:2019 - Petroleum and natural gas industries - General requirements for offshore structures (ISO 19900:2019)

Relations

• Replaces: EN ISO 19900:2013 - Petroleum and natural gas industries - General requirements for offshore structures (ISO 19900:2013)
• Effective Date: 17-Jul-2019
• Revised: prEN ISO 19900 - Oil and gas industries including lower carbon energy - General requirements for offshore structures (ISO/DIS 19900:2025)
• Effective Date: 12-Mar-2025

Overview

EN ISO 19900:2019 (ISO 19900:2019) establishes the general requirements and recommendations for the design and assessment of offshore structures used in the petroleum and natural gas industries. It applies to both bottom-founded (fixed) and buoyant (floating) structures across all life phases - fabrication, transportation, installation, in‑service operation (including life extensions), and decommissioning/removal. The standard covers new-build design as well as structural integrity management and assessment of existing platforms. It does not apply to subsea/riser systems or pipeline systems.

Keywords: ISO 19900, offshore structures, petroleum and natural gas industries, design and assessment, structural integrity.

Key Topics and Technical Requirements

• Fundamental requirements for structural integrity, functionality, durability and robustness throughout the structure’s life cycle.
• Basis for design/assessment: site location, orientation, physical environmental conditions and geotechnical/geophysical investigation requirements.
• Development of design/assessment situations including classification of hazards, exposure levels, and operational/abnormal/extreme/accidental situations.
• Limit state verification framework covering ultimate, serviceability, fatigue and accidental limit states; procedures for verification and representative values.
• Actions and loading: classification and representative values for permanent, operational, environmental and accidental actions, and repetitive loading relevant to offshore platforms.
• Design values and partial factors covering actions, resistances and combinations for limit state checks.
• Specific design considerations referenced for topsides, deck elevation, splash zone, stationkeeping systems, foundations/anchoring and conductor/ structural interfaces.
• Requirements for planning, construction, deployment, inspection, maintenance and decommissioning to support durability and structural integrity management.

Keywords: limit states, environmental actions, design values, partial factors, fatigue, geotechnical conditions.

Practical Applications

• Establishing the design basis and verification approach for new offshore platforms (fixed or floating).
• Conducting structural integrity assessments and fitness‑for‑service evaluations for existing installations and life‑extension projects.
• Developing inspection, maintenance and decommissioning plans consistent with durability and robustness requirements.
• Supporting regulatory compliance, class society certification and operator risk management by defining actions, combinations and limit‑state procedures.

Keywords: structural integrity management, life‑cycle, inspection, decommissioning, offshore platform design.

Who Should Use This Standard

• Offshore structural, marine and civil engineers
• Asset owners and operators in the petroleum and natural gas industries
• Class societies and regulatory authorities
• Inspection, maintenance and integrity management teams
• Fabricators and contractors involved in construction, transport and installation

Related Standards

This document is the general‑requirements reference in the ISO/CEN offshore standards family and is typically used alongside platform‑type and discipline‑specific standards and guidance for metocean, geotechnical and equipment design.

Keywords: ISO offshore standards, EN ISO 19900, offshore design guidance.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2019
Nadomešča:
SIST EN ISO 19900:2014
Industrija za predelavo nafte in zemeljskega plina - Splošne zahteve za vrtalne
ploščadi (ISO 19900:2019)
Petroleum and natural gas industries - General requirements for offshore structures (ISO
19900:2019)
Erdöl- und Erdgasindustrie - Allgemeine Anforderungen an Offshore-Bauwerke (ISO
19900:2019)
Industries du pétrole et du gaz naturel - Exigences générales relatives aux structures en
mer (ISO 19900:2019)
Ta slovenski standard je istoveten z: EN ISO 19900:2019
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 19900
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2019
EUROPÄISCHE NORM
ICS 75.180.10 Supersedes EN ISO 19900:2013
English Version
Petroleum and natural gas industries - General
requirements for offshore structures (ISO 19900:2019)
Industries du pétrole et du gaz naturel - Exigences Erdöl- und Erdgasindustrie - Allgemeine
générales relatives aux structures en mer (ISO Anforderungen an Offshore-Bauwerke (ISO
19900:2019) 19900:2019)
This European Standard was approved by CEN on 9 June 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19900:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 19900:2019) has been prepared by Technical Committee ISO/TC 67 "Materials,
equipment and offshore structures for petroleum, petrochemical and natural gas industries" in
collaboration with Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for
petroleum, petrochemical and natural gas industries” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2020, and conflicting national standards shall
be withdrawn at the latest by January 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 19900:2013.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 19900:2019 has been approved by CEN as EN ISO 19900:2019 without any modification.

INTERNATIONAL ISO
STANDARD 19900
Third edition
2019-06
Petroleum and natural gas
industries — General requirements
for offshore structures
Industries du pétrole et du gaz naturel — Exigences générales
relatives aux structures en mer
Reference number
ISO 19900:2019(E)
©
ISO 2019
ISO 19900:2019(E)
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

ISO 19900:2019(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 8
4.1 Symbols . 8
4.2 Abbreviated terms . 9
5 Fundamental requirements . 9
5.1 General . 9
5.2 Structural integrity requirements .10
5.3 Functional requirements .10
5.4 Requirements for specific phases of the life of the structure .11
5.4.1 Planning .11
5.4.2 Construction and deployment .11
5.4.3 Structural integrity management .11
5.4.4 Decommissioning and removal .11
5.5 Requirements for durability and robustness .12
5.5.1 Durability, maintenance and inspection .12
5.5.2 Robustness .12
6 Basis for design/assessment .13
6.1 General .13
6.2 Platform location and orientation .13
6.3 Physical environmental conditions .14
6.4 Geotechnical and geophysical conditions .14
6.4.1 Marine site investigations .14
6.4.2 Seabed instability .15
6.4.3 Seabed disturbance .15
6.5 Specific design/assessment requirements .16
6.5.1 Topsides structures .16
6.5.2 Deck elevation .16
6.5.3 Splash zone .17
6.5.4 Stationkeeping systems .17
6.5.5 Conductor and riser systems .17
6.5.6 Foundations and anchoring .17
6.5.7 Additional operational requirements .18
7 Development of design/assessment situations.18
7.1 Hazards .18
7.2 Hazardous events.18
7.3 Exposure levels .19
7.3.1 General.19
7.3.2 Exposure level L1 .20
7.3.3 Exposure level L2 .20
7.3.4 Exposure level L3 .20
7.4 Design/assessment situations .21
7.4.1 General.21
7.4.2 Operational design/assessment situations .21
7.4.3 Extreme design/assessment situations .22
7.4.4 Abnormal design/assessment situations .22
7.4.5 Accidental design/assessment situations .23
7.4.6 Short duration design/assessment situations .23
7.4.7 Serviceability design/assessment situations .24
ISO 19900:2019(E)
8 Limit state verification .24
8.1 General .24
8.2 Basic variables and representative values .25
8.3 Limit states .26
8.3.1 Categories of limit states .26
8.3.2 Ultimate limit states .26
8.3.3 Abnormal/accidental limit states.27
8.3.4 Serviceability limit states .27
8.3.5 Fatigue limit states .27
8.4 Limit state verification procedure .28
9 Actions .28
9.1 Classifications of actions .28
9.2 Permanent actions and their representative values .29
9.3 Operational actions and their representative values .29
9.4 Environmental actions and their representative values .30
9.5 Accidental actions and their representative values .31
9.6 Repetitive actions .31
10 Design values and partial factors .32
10.1 Design values of actions .32
10.2 Actions acting in combination .32
10.2.1 Principal and companion actions for the same action type .32
10.2.2 Principal and accompanying actions for specific design/assessment situations .33
10.3 Design values of resistance .33
10.3.1 General.33
10.3.2 Design values of materials including soils .33
10.3.3 Design values of geometric variables .34
10.3.4 Uncertainties in analysis models .34
10.4 Partial factors for operational and extreme design/assessment situations .34
10.5 Partial factors for abnormal and accidental design/assessment situations .34
10.6 Partial factors for serviceability design/assessment situations .35
10.7 Partial factors for fatigue design/assessment verification .35
10.8 Probabilistic modelling and analysis .35
11 Models and analysis .35
12 Quality management .36
12.1 General .36
12.2 Installation inspection .36
12.3 In-service inspection, maintenance and repair .36
12.4 Records and documentation of design and construction .37
12.4.1 General.37
12.4.2 Calculations .37
12.4.3 Weight and centre of gravity reports .38
12.4.4 Drawings and specifications .38
13 Assessment of existing structures .38
13.1 General .38
13.2 Condition assessment .39
13.2.1 General.39
13.2.2 Service and operating requirements .39
13.2.3 Environmental conditions .39
13.2.4 Testing, inspection, maintenance and repair history .39
13.3 Action assessment .40
13.4 Resistance assessment .40
13.5 Component and system failure consequences .40
13.6 Mitigation.40
Annex A (informative) Additional information and guidance .41
Bibliography .64
iv © ISO 2019 – All rights reserved

ISO 19900:2019(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document 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.
This third edition cancels and replaces the second edition (ISO 19900:2013), which has been technically
revised. The main changes compared to the previous edition are as follows:
— Terms and definitions have been updated;
— Design/assessment situations are described, and the process for limit state design/assessment
verification has been clarified;
— Contents have been reorganized and many clarifications to provisions have been made;
— Annex A has been reorganized to mirror the numbering of the normative clauses and it has been
updated with substantial guidance moved from normative clauses.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
ISO 19900:2019(E)
Introduction
The International Standards on offshore structures prepared by TC 67/SC 7 (i.e. ISO 19900, the
ISO 19901 series, ISO 19902, ISO 19903, ISO 19904-1, the ISO 19905 series, ISO 19906) constitute a
common basis addressing design requirements and assessments of all types of offshore structures
used by the petroleum and natural gas industries worldwide.
NOTE These are sometimes referred to as the ISO 19900 series on offshore structures.
Through their application, the intention is to achieve adequate structural integrity and performance
based on reliability levels appropriate for manned and unmanned offshore structures, whatever the
nature or combination of the materials used.
Structural integrity is an overall concept comprising: models for describing actions, structural
analyses, design rules, safety elements, workmanship, quality management, and national requirements,
all of which are mutually dependent. The modification of any of these elements in isolation can cause an
imbalance or inconsistency, with possible impact on the reliability inherent in the offshore structure.
The implications involved in modifying one element, therefore, need to be considered in relation to all
the elements and the overall reliability of the offshore structure.
The International Standards on offshore structures prepared by TC 67/SC 7 are intended to provide
latitude in the choice of structural configurations, materials and techniques and to allow for innovative
solutions. Sound engineering judgement is, therefore, necessary in the use of these documents.
Figure 1 gives a general indication of the relationships between the International Standards on offshore
structures prepared by TC 67/SC 7.
This document, i.e. ISO 19900, follows the principles of ISO 2394 and is the unifying document for
International Standards on offshore structures prepared by TC 67/SC 7, which encompass both
specific requirements for offshore structures (the ISO 19901 series) and “structure type” documents
(ISO 19902, ISO 19903, ISO 19904-1, ISO 19905-1, ISO 19905-3, and ISO 19906).
The ISO 19901 series addresses particular aspects of the design, construction, and operation of offshore
structures for the petroleum and natural gas industries. The provisions can be applicable to structures
of different types, materials and operating environments.
In addition to the relationships between the “structure type” documents and the ISO 19901 series, there
is also some interdependence among the “structure type” documents, in that one can reference another,
e.g. ISO 19906 on arctic offshore structures builds upon the requirements of ISO 19902 on fixed steel
offshore structures.
In ISO 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;
— “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.
Additional information and guidance are given in Annex A, where the clause numbering mirrors the
normative clauses to facilitate cross referencing.
vi © ISO 2019 – All rights reserved

ISO 19900:2019(E)
Figure 1 — Relationship of International Standards on offshore structures prepared by TC67/SC7
INTERNATIONAL STANDARD ISO 19900:2019(E)
Petroleum and natural gas industries — General
requirements for offshore structures
1 Scope
This document specifies general requirements and recommendations for the design and assessment of
bottom-founded (fixed) and buoyant (floating) offshore structures.
This document is applicable for all phases of the life of the structure, including:
— successive stages of construction (i.e. fabrication, transportation, and installation),
— service in-place, both during design life and during any life extensions, and
— decommissioning, and removal.
This document contains general requirements and recommendations for both the design of new build
structures and for the structural integrity management and assessment of existing structures.
This document does not apply to subsea and riser systems or pipeline systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 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
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
ISO 19901-8, Petroleum and natural gas industries — Specific requirements for offshore structures —
Part 8: Marine soil investigations
ISO 19901-9, Petroleum and natural gas industries — Specific requirements for offshore structures — Part
9: Structural integrity management
ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures
ISO 19903, Petroleum and natural gas industries — Concrete offshore structures
ISO 19900:2019(E)
ISO 19904-1, Petroleum and natural gas industries — Floating offshore structures — Part 1: Monohulls,
semisubmersibles and spars
ISO 19905-1, Petroleum and natural gas industries — Site-specific assessment of mobile offshore units —
Part 1: Jack-ups
ISO 19905-3, Petroleum and natural gas industries — Site-specific assessment of mobile offshore units —
Part 3: Floating unit
ISO 19906, Petroleum and natural gas industries — Arctic offshore structures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
abnormal environmental event
−3
environmental hazardous event (3.27) having probability of occurrence not greater than 10 per
annum (1 in 1 000 years)
3.2
accidental event
−3
non-environmental hazardous event (3.27) having probability of occurrence not greater than 10 per
annum (1 in 1 000 years)
Note 1 to entry: Accidental events, as referred to in this document, are associated with a substantial release of
energy, such as vessel collisions, fires, and explosions.
Note 2 to entry: Lesser accidents that could be expected during the life of the structure, such as dropped objects
and low energy vessel impact, are termed incidents and are addressed under operational design situations.
3.3
action
external load applied to the structure (3.53) (direct action) or an imposed deformation or acceleration
(indirect action)
EXAMPLE An imposed deformation can be caused by fabrication tolerances, differential settlement,
temperature change or moisture variation. An imposed acceleration can be caused by an earthquake.
3.4
action effect
result of actions (3.3) on a structural component (3.49) (e.g. internal force, moment, stress, strain) or on
the structure (3.53) (e.g. deflection, rotation)
3.5
air gap
distance between the highest water elevation and the lowest exposed part of the primary deck structure
(3.53) not designed to withstand associated environmental action effects (3.4) for a defined return
period (3.42)
Note 1 to entry: This definition can be refined for different platform types in their respective standards.
2 © ISO 2019 – All rights reserved

ISO 19900:2019(E)
3.6
appurtenance
accessory or attachment to the structure (3.53) which typically assists installation, provides access or
protection, or carries fluids or gas
Note 1 to entry: Appurtenances do not normally contribute to the stiffness of the structure but can attract
significant hydrodynamic loading.
EXAMPLE Riser, caisson, boat landing, fender, and protection frames.
3.7
basic variable
variable representing physical quantities which characterize actions (3.3) and environmental
influences, geometric quantities, or material properties including soil properties
Note 1 to entry: Basic variables are typically uncertain random variables or random processes used in the
calculation or assessment of representative values of actions or resistance.
3.8
calibration
process used to determine and optimize partial factors using structural reliability analysis (3.52) and
target reliabilities
3.9
characteristic value
value assigned to a basic variable (3.7) with a prescribed probability
Note 1 to entry: In some design/assessment situations, a variable can have two characteristic values, an upper
value and a lower value.
3.10
conductor
tubular pipe set into the ground to provide the initial stable structural foundation for setting the
surface casing and protecting the internal well string from metocean actions
Note 1 to entry: The conductor provides lateral and, in some cases, axial support, enables circulation of drilling
fluid, and guides the drill string to facilitate setting of the surface casing.
3.11
decommissioning
process of shutting down a platform (3.37) enabling preparations for cleaning, dismantling and/or
removal from location at the end of total service life (3.18)
3.12
design resistance
resistance limit calculated using factored representative values (3.40) of basic variables (3.7) or from
factored expressions based on unfactored representative values (3.40) of basic variables (3.7)
EXAMPLE Examples of basic variables relevant to resistance are material properties.
3.13
design service life
planned period for which a structure (3.53) is used for its intended purpose with anticipated
maintenance, but without substantial repair being necessary
3.14
design value
value derived from the representative value (3.40) for use in limit state verification (3.32)
Note 1 to entry: Design values can be different in different design/assessment situations due to different partial
factors.
ISO 19900:2019(E)
3.15
design/assessment criteria
quantitative formulations describing the conditions to be fulfilled for each design/assessment
situation (3.16)
3.16
design/assessment situation
set of physical conditions for which the structure (3.53) or its components are verified
3.17
deterioration
process that adversely affects structural integrity (3.50) over time
Note 1 to entry: Deterioration can be caused by naturally occurring chemical, physical, or biological actions
including corrosion, by severe environmental actions, by incidents and accidental actions, by repeated actions
such as those causing fatigue, by wear due to use, and by improper operation and maintenance of the structure.
3.18
total service life
design service life (3.13) plus any subsequent operational life extension period(s)
3.19
durability
ability of a structure (3.53) or structural component (3.49) to maintain its function throughout its total
service life (3.18)
3.20
exposure level
classification system used to establish relevant criteria for a structure (3.53) based on consequences
of failure
3.21
extreme environmental event
−2
environmental hazardous event (3.27) typically having probability of occurrence of 10 per annum (1
in 100 years)
3.22
fit-for-service
fulfilling defined structural integrity (3.50) and performance (3.36) requirements
Note 1 to entry: A structure not meeting all the specific provisions can be fit-for-service, provided it does not
cause unacceptable risk to life-safety or the environment.
3.23
fitness-for-service assessment
engineering evaluations to demonstrate that a structure (3.53) or a structural component (3.49) which
deviates from its design basis, is fit-for-service (3.22)
Note 1 to entry: Deviations can include deterioration or damage, life extension, and other changes and
modifications to the structure or to the design basis.
3.24
fixed structure
structure (3.53) that is bottom founded and transfers most of the actions (3.3) on it to the seabed (3.47)
3.25
floating structure
structure (3.53) where the full weight is supported by buoyancy
4 © ISO 2019 – All rights reserved

ISO 19900:2019(E)
3.26
hazard
potential source of harm
Note 1 to entry: Harm is typically differentiated between harm to people, harm to the environment, or harm in
terms of costs to organization(s) or society in general.
3.27
hazardous event
event which occurs when a hazard (3.26) interacts with a structure (3.53)
EXAMPLE Wave impacting the structure, iceberg impacting the structure, excessive topside weight added to
the structure, vessel collision, fire, explosion, and landslip in the vicinity of structural anchors (piles).
3.28
ice gouge
ice scour
incision in the seabed (3.47) or removal of seabed material by an ice feature
3.29
incident
non-environmental hazardous event (3.27) considered in an operational design/assessment situation (3.16)
Note 1 to entry: Incident, as referred to in this document, is a lesser accidental event, associated with possible
local damage or damage to structural components, occurring with low probability, most typically associated
−2
with probabilities not less than 10 per annum (1 in 100 years).
3.30
jack-up
mobile offshore unit with a buoyant hull and one or more legs that can be moved up and down relative
to the hull
Note 1 to entry: A jack-up reaches its operational mode by lowering the leg(s) to the seabed and then raising
the hull to the required elevation. The majority of jack-ups have three or more legs, each of which can be moved
independently and which are supported in the seabed by spudcans.
3.31
limit state
state beyond which the structure (3.53) or structural component (3.49) no longer satisfies the design/
assessment criteria (3.15)
3.32
limit state verification
demonstration that the total design action effect (3.4) in each design/assessment situation (3.16) does
not exceed the limit state (3.31) design resistance (3.12)
3.33
nominal value
value assigned to a variable specified or determined on a non-statistical basis, typically from acquired
experience or physical conditions, or as published in a recognized code or standard
Note 1 to entry: In some design/assessment situations, a variable can have two nominal values, an upper value
and a lower value.
3.34
offshore
situated in water some distance from the shore
Note 1 to entry: Alternatively, near shore can be used to specify locations next to the coast or in mouths of rivers.
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