oSIST prEN ISO 19900:2025

Oil and gas industries including lower carbon energy - General requirements for offshore structures (ISO/DIS 19900:2025)

This document specifies general provisions for the design and assessment of fixed (bottom-founded)  and floating (buoyant) offshore structures.
This document contains general provisions for the design of new structures and site assessment of existing structures.
This document is applicable for all phases of the life of the structure, including:
¾    pre-service (e.g., fabrication, transportation, installation),
¾    service in-place, both during originally specified design service life and during any life extensions,
¾    functional upgrade, repurpose and reuse, and
¾    decommissioning, and removal.
This document focusses on primary and secondary load bearing structure but also provides some provisions for tertiary and ancillary structure.
NOTE         ISO 24201[22] covers the design of stairs, gratings and handrails.
This document was initially created for offshore oil & gas structures but is now also applicable to renewable energy offshore structures.
This document does not apply to pipelines, risers or subsea systems.

Öl- und Gasindustrie einschließlich kohlenstoffarmer Energieträger - Allgemeine Anforderungen an Offshore-Bauwerke (ISO/DIS 19900:2025)

Industries du pétrole et du gaz, y compris les énergies à faible teneur en carbone - Exigences générales relatives aux structures en mer (ISO/DIS 19900:2025)

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.

Naftna in plinska industrija, vključno z nizkoogljično energijo - Splošne zahteve za vrtalne ploščadi (ISO/DIS 19900:2025)

General Information

• Status: Not Published
• Public Enquiry End Date: 14-Dec-2025
• ICS: 75.180.10 - Exploratory, drilling and extraction equipment
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 21-Oct-2025
• Due Date: 10-Mar-2026
• Completion Date: 15-Dec-2025
• Ref Project: prEN ISO 19900 - Oil and gas industries including lower carbon energy - General requirements for offshore structures (ISO/DIS 19900:2025)

Relations

• Revises: SIST EN ISO 19900:2019 - Petroleum and natural gas industries - General requirements for offshore structures (ISO 19900:2019)
• Effective Date: 12-Mar-2025

Overview

The oSIST prEN ISO 19900:2025:2025 standard, titled "Oil and gas industries including lower carbon energy - General requirements for offshore structures", provides comprehensive guidelines for the design and assessment of offshore fixed (bottom-founded) and floating (buoyant) structures. Published by CEN, this draft international standard applies across all lifecycle phases of offshore structures-covering fabrication, transportation, installation, in-service operations, functional upgrades, repurposing, reuse, as well as decommissioning and removal. Initially developed for offshore oil and gas platforms, the scope now embraces offshore renewable energy structures, reflecting evolving industry trends toward lower-carbon energy sources.

Excluding pipelines, risers, and subsea systems, the standard emphasizes primary and secondary load-bearing elements, while also addressing tertiary and ancillary structural requirements. It establishes a modern foundation for ensuring safety, sustainability, and robustness in offshore structural design amid increasingly complex environmental and operational challenges.

---

Key Topics

• Design Scope and Lifecycle Phases
  Covers all design phases including pre-service (fabrication, transportation, installation), in-service operation including lifespan extensions, upgrades, and decommissioning processes.

• Structural Types
  Applies to both bottom-founded (fixed) and buoyant (floating) offshore structures, accommodating conventional oil and gas platforms as well as newer renewable energy installations.

• Design Considerations
  Focuses on functional and operational requirements, robustness, durability, sustainability, and quality management throughout the structure's life cycle.

• Load and Action Characterization
  Defines environmental, operational, accidental, and repetitive actions affecting offshore structures, and prescribes combinations and classifications to guide design safety margins.

• Limit States and Performance Criteria
  Details ultimate, serviceability, and fatigue limit states for performance verification ensuring structural integrity under varied conditions.

• Design Methodologies
  Recommends semi-probabilistic design approaches using partial factor methods, with allowance for alternative methods and comprehensive risk mitigation strategies.

• Structural and Geotechnical Basis
  Addresses site-specific considerations such as location, orientation, environmental loads, geotechnical conditions, and inspection feasibility.

• Sustainability and Low Carbon Energy Integration
  Reflects the evolving industry landscape by including requirements applicable to offshore renewable energy platforms, complementing the traditional oil and gas sector.

---

Applications

• Offshore Oil & Gas Platforms
  Supports the design and ongoing assessment of fixed and floating oil extraction and processing structures, optimizing safety and operational reliability.

• Renewable Energy Structures
  Extends applicability to offshore wind turbines and other lower-carbon energy installations providing a unified framework for multi-energy offshore developments.

• Structural Lifecycle Management
  Facilitates comprehensive lifecycle management including fabrication, installation, service life, upgrade possibilities, and safe decommissioning.

• Engineering and Project Management
  Assists engineers and project managers in meeting regulatory requirements, improving design optimization, enhancing robustness, and implementing risk mitigation.

• Regulatory Compliance and Industry Standardization
  Offers a harmonized international benchmark supporting regulatory frameworks and ensuring interoperability among global offshore engineering projects.

---

Related Standards

• ISO 24201
  Covers specific design requirements for offshore stairways, gratings, and handrails complementing the structural scope of ISO 19900.

• ISO 19902
  Provides additional specifications on fixed steel offshore structures, building on the general provisions set by ISO 19900.

• ISO 19903 & ISO 19904 Series
  Govern design criteria for concrete offshore structures and floating offshore structures, respectively, extending structural design coverage.

• ISO 23970
  Focuses on environmental conditions and metocean data supporting load analysis as referenced in ISO 19900.

• API RP 2A
  While not an ISO standard, the American Petroleum Institute’s recommended practice may align with ISO 19900 principles for offshore structure design.

---

By incorporating the oSIST prEN ISO 19900:2025:2025 requirements, offshore engineers and stakeholders can ensure their structures achieve high standards of safety, reliability, and environmental stewardship in oil, gas, and renewable energy projects worldwide. This standard plays a pivotal role in advancing offshore structural design toward a safer, greener future.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2025
Naftna in plinska industrija, vključno z nizkoogljično energijo - Splošne zahteve za
vrtalne ploščadi (ISO/DIS 19900:2025)
Oil and gas industries including lower carbon energy - General requirements for offshore
structures (ISO/DIS 19900:2025)
Öl- und Gasindustrie einschließlich kohlenstoffarmer Energieträger - Allgemeine
Anforderungen an Offshore-Bauwerke (ISO/DIS 19900:2025)
Industries du pétrole et du gaz, y compris les énergies à faible teneur en carbone -
Exigences générales relatives aux structures en mer (ISO/DIS 19900:2025)
Ta slovenski standard je istoveten z: prEN ISO 19900
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.

DRAFT
International
Standard
ISO/DIS 19900
ISO/TC 67/SC 7
Oil and gas industries including
Secretariat: BSI
lower carbon energy — General
Voting begins on:
requirements for offshore
2025-10-01
structures
Voting terminates on:
ICS: 75.180.10
2025-12-24
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 19900:2025(en)
DRAFT
ISO/DIS 19900:2025(en)
International
Standard
ISO/DIS 19900
ISO/TC 67/SC 7
Oil and gas industries including
Secretariat: BSI
lower carbon energy — General
Voting begins on:
requirements for offshore
structures
Voting terminates on:
ICS: 75.180.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
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TO SUBMIT, WITH THEIR COMMENTS,
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NOTIFICATION OF ANY RELEVANT PATENT
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RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 19900:2025(en)
ii
ISO/DIS 19900:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 8
4.1 Symbols .8
4.2 Abbreviated terms .9
5 Design considerations . 9
5.1 Functional and operational requirements .9
5.2 Consequence levels .10
5.3 Robustness .11
5.4 Durability .11
5.5 Sustainability . 12
5.6 Quality management . 12
6 Basis of structural and geotechnical design .12
6.1 Facility location and orientation . 12
6.2 Weights . 13
6.3 Geotechnical and geophysical conditions . 13
6.4 Environmental conditions . 13
6.5 Accidental conditions .14
6.6 Topsides structures, air gap and splash zone .14
6.7 Ancillary systems .14
6.8 Inspectability . 15
6.9 Jack-ups . 15
6.10 Non-oil & gas facilities . 15
7 Development of design situations .16
7.1 Hazardous events .16
7.2 Design situations .16
8 Limit states and structure performance . .18
8.1 General .18
8.2 Ultimate limit states .18
8.3 Serviceability limit states .19
8.4 Fatigue limit states .19
8.5 Alternative methods for demonstrating structure performance .19
9 Characterization of actions and resistance. 19
9.1 Basic variables .19
9.2 Classifications of actions . 20
9.3 Permanent actions . 20
9.4 Operational actions . 20
9.5 Environmental actions . 20
9.6 Accidental actions .21
9.7 Repetitive actions .21
9.8 Actions acting in combination .21
9.8.1 General .21
9.8.2 Principal actions . 22
9.8.3 Companion actions . 22
9.8.4 Accompanying actions . 22
9.9 Structural resistance . 23
9.9.1 Material properties . 23
9.9.2 Geometrical properties . 23

iii
ISO/DIS 19900:2025(en)
9.9.3 Resistance to repetitive actions . 23
10 Design approaches .23
10.1 Design principles and approaches for offshore structures. 23
10.2 Semi-probabilistic approach .24
10.3 Alternative approaches . 25
10.4 Risk mitigation . 26
11 Design values for semi-probabilistic approach .27
11.1 Partial factor method for offshore structures .27
11.2 Hazardous events .27
11.3 Representative values .27
11.4 Actions . 28
11.4.1 Representative values of permanent actions . 28
11.4.2 Representative values of operational actions . 28
11.4.3 Representative values of environmental actions . 28
11.4.4 Representative values of accidental actions . 29
11.4.5 Partial factors for actions . 29
11.4.6 Actions acting in combination . 29
11.4.7 Design values of actions and action effects . 30
11.5 Resistance . 30
11.5.1 Representative values for material properties . 30
11.5.2 Representative values for geometrical properties . 30
11.5.3 Design value of material variables .31
11.5.4 Design value of geometric variables .31
11.5.5 Design resistance .31
11.5.6 Partial factors for materials and resistance .32
11.5.7 Resistance for repetitive actions .32
11.6 Verification by the partial factor method .32
11.6.1 Verification of ULS .32
11.6.2 Verification of SLS . 33
11.6.3 Verification of FLS . 33
12 Structural modelling and analysis .33
12.1 Structural modelling . 33
12.1.1 General principles of structural and geotechnical modelling . 33
12.1.2 Static actions . 34
12.1.3 Dynamic actions . 34
12.1.4 Actions inducing fatigue . 34
12.1.5 Fire and explosion design . 35
12.2 Structural analysis . 35
12.2.1 General . 35
12.2.2 Linear analysis . 36
12.2.3 Non-linear analysis . 36
12.3 Design assisted by testing . 36
13 Integrity management and assessment of existing structures and marine systems.37
13.1 General .37
13.2 Integrity management of structures and marine systems .37
13.3 Assessment of existing structures and marine systems. 38
13.4 Assessment situations and approaches . 39
Annex A (informative) Additional information and guidance .40
Bibliography . 74

iv
ISO/DIS 19900:2025(en)
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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, Oil and gas industries including lower carbon
energy, Subcommittee SC 7, Offshore structures.
This fourth edition cancels and replaces the third edition (ISO 19900:2019), which has been technically
revised. The main changes compared to the previous edition are as follows:
— ensuring the provisions herein are appropriate for offshore renewable energy, in particular, offshore
wind turbine and sub-station structures;
— specifying clear, concise and verifiable requirements, while providing more extensive supporting
background and informative guidance in the informative Annex A;
— providing greater explanation for design and assessment in situations where the semi-probabilistic
partial factor approach is not appropriate.
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.

v
ISO/DIS 19900:2025(en)
Introduction
The International Standards for offshore structures prepared by ISO TC 67/SC 7 comprise:
— ISO 19900, the unifying International Standard for offshore structures.
[6 to 12]
— ISO 19901 series , providing specific requirements for offshore structures.
[13] [14] [15] [16 to 19] [20]
— ISO 19902, ISO 19903, ISO 19904, ISO 19905 and ISO 19906 , “structure type”
standards.
NOTE These are collectively referred to as the “ISO 19900 suite” for offshore structures.
Figure 1 illustrates the relationships between the standards in the ISO 19900 suite.
Figure 1 — Relationship of Standards for offshore structures prepared by ISO/TC 67/SC 7
[1] [21]
The ISO 19900 suite follows the principles of ISO 2394 and ISO 22111 and constitutes a common basis
for addressing design and assessment of all types of offshore structures used by the energy industries
worldwide. Additional information and guidance are given in Annex A, where the clause numbering mirrors
the normative clauses to facilitate cross referencing.
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

vi
ISO/DIS 19900:2025(en)
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.
Statements containing requirements, recommendations or permissions are collectively referred to as
provisions.
vii
DRAFT International Standard ISO/DIS 19900:2025(en)
Oil and gas industries including lower carbon energy —
General requirements for offshore structures
1 Scope
This document specifies general provisions for the design and assessment of fixed (bottom-founded) and
floating (buoyant) offshore structures.
This document contains general provisions for the design of new structures and site assessment of existing
structures.
This document is applicable for all phases of the life of the structure, including:
— pre-service (e.g., fabrication, transportation, installation),
— service in-place, both during originally specified design service life and during any life extensions,
— functional upgrade, repurpose and reuse, and
— decommissioning, and removal.
This document focusses on primary and secondary load bearing structure but also provides some provisions
for tertiary and ancillary structure.
[22]
NOTE ISO 24201 covers the design of stairs, gratings and handrails.
This document was initially created for offshore oil & gas structures but is now also applicable to renewable
energy offshore structures.
This document does not apply to pipelines, risers or subsea 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.
NOTE Regional or national adoptions of ISO standards are equivalent normative references to those listed below.
In USA, API SC2Offshore Structures, publish a mix of standards that are adoptions of ISO standards and standards that
are unique API SC2 publications. The cover page to each ANSI/API Standard clarifies if it is an ISO adopted standard.
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, Oil and gas industries including lower carbon energy — Specific requirements for offshore
structures — Part 3: Topsides structure
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO/DIS 19900:2025(en)
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 https:// www .electropedia .org/
3.1
abnormal environmental event
−3
environmental hazardous event (3.31) having probability of occurrence not greater than 10 per annum (1
in 1 000 years)
3.2
accidental event
−3
non-environmental hazardous event (3.31) 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 (3.60) (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 (3.57) (e.g. internal force, moment, stress, strain) or on the
structure (3.60) (e.g. deflection, rotation)
3.5
air gap
distance between the highest water elevation and the lowest exposed part of the primary deck structure (3.60)
not designed to withstand associated environmental action effects (3.3) for a defined return period (3.50)
Note 1 to entry: This definition can be refined for different facility types in their respective standards.
3.6
appurtenance
accessory or attachment to the structure (3.60) 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.

ISO/DIS 19900:2025(en)
3.8
caisson
vertical cylindrical steel component within or mounted on an offshore facility (3.26)
Note 1 to entry: Caissons serve many different functions at different locations on an offshore facility. More specific
definitions for each type of caisson are specified within the other standards in the ISO 19900 suite of standards.
3.9
calibration
process used to determine and optimize partial factors using structural reliabilityanalysis (3.59) and target
reliabilities
3.10
characteristic value
value assigned to a basic variable (3.7) with a prescribed probability
Note 1 to entry: In some design situations, a variable can have two characteristic values, an upper value and a lower value.
3.11
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.
3.12
consequence level
classification system used to establish relevant criteria for a structure (3.60) based on consequences of failure
3.13
damage state
discrete state that describes the level of impairment
Note 1 to entry: Damage states can be categorized between no damage and complete loss of structure or marine
systems.
3.14
decommissioning
process of shutting down a facility (3.26) enabling preparations for cleaning, dismantling and removal from
location at the end of its design service life (3.17)
3.15
design criteria
assessment criteria
quantitative formulations describing the conditions to be fulfilled for each design situation (3.18)
3.16
design resistance
resistance limit calculated using factored representative values (3.48) of basic variables (3.7) or from factored
expressions based on unfactored representative values (3.48) of basic variables (3.7)
EXAMPLE Examples of basic variables relevant to resistance are material properties.
3.17
design service life
design life
planned period for which a structure (3.60) is used for its intended purpose with anticipated maintenance,
but without substantial repair being necessary
Note 1 to entry: The originally specified design service life can be updated during the operating phase to include any
life extension period(s).
ISO/DIS 19900:2025(en)
3.18
design situation
set of physical conditions for which the structure (3.60) or its components are verified
3.19
design value
value derived from the representative value (3.48) for use in limit state verification (3.37)
Note 1 to entry: Design values can be different in different design situations due to different partial factors.
3.20
deterioration
process that adversely affects structural integrity (3.58) 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.
3.21
ductility
ability of a material to deform and absorb energy beyond its elastic limit
3.22
ductility
ability of a structural component (3.57) to sustain action effects (3.4) beyond yield
3.23
ductility
ability of a structural system to deform and dissipate energy, and to redistribute action
effects (3.4)
3.24
durability
ability of a structure (3.60) or structural component (3.57) to maintain its function throughout its design
service life (3.17)
3.25
extreme environmental event
−2
environmental hazardous event (3.31) typically having probability of occurrence of 10 per annum (1 in
100 years)
3.26
facility
constructions, pieces of equipment, and services that are provided for the offshore energy sector
Note 1 to entry: The facility includes the structure and non-structural systems such as topsides equipment, piping and
accommodation.
Note 2 to entry: A hydrocarbon facility (platform) includes the structural conductors and risers but does not include
the non-structural components of the hydrocarbon wells.
Note 3 to entry: The facility does not include the geological strata supporting the foundation. However, site-specific
geotechnical parameters provide the boundary conditions necessary to model the facility’s foundation or anchoring.
3.27
fit-for-service
fulfilling defined structural integrity (3.58) and performance (3.43) 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.

ISO/DIS 19900:2025(en)
3.28
fixed structure
structure (3.60) that is bottom founded and transfers most of the actions (3.3) on it to the seabed (3.55)
3.29
floating structure
structure (3.60) where the full weight is supported by buoyancy
3.30
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.
3.31
hazardous event
event which occurs when a hazard (3.30) interacts with a structure (3.60)
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).
3.32
ice gouge
ice scour
incision in the seabed (3.55) or removal of seabed material by an ice feature
3.33
incident
non-environmental hazardous event (3.31) considered in an operational design situation (3.18)
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 with
−2
probabilities not less than 10 per annum (1 in 100 years).
3.34
integrity management
systematic multi-step cyclic process intended to assure integrity of a structure (3.60) or a marine system (3.38)
3.35
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.
3.36
limit state
state beyond which the structure (3.60) or structural component (3.57) no longer satisfies the design
criteria (3.15)
3.37
limit state verification
demonstration that the total design action effect (3.4) in each design situation (3.18) does not exceed the limit
state (3.36) design resistance (3.16)
3.38
marine system
auxiliary system contributing to the structural safety, stability and position keeping ability of the facility (3.26)

ISO/DIS 19900:2025(en)
3.39
marine system integrity
ability of a marine system (3.38) to maintain performance (3.43) throughout the design service life (3.17),
with respect to structural safety, robustness (3.52), serviceability, and durability (3.24)
3.40
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 situations, a variable can have two nominal values, an upper value and a lower value.
3.41
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.
3.42
owner
operator
duty holder
principal company or company representative leasing the offshore site from a government
3.43
performance
ability of a structure (3.60) or a structural component (3.57) to fulfil specified requirements
Note 1 to entry: Specified requirements include requirements for structural functionality, structural integrity and
functionality of critical systems.
Note 2 to entry: Performance levels are established as a means of mitigating risk associated with life-safety,
environmental damage, reliability of energy supply and business disruption.
3.44
principal action
action caused by the hazardous event or other source of action for which the design situation has been
established
Note 1 to entry: Principal actions can consist of operational, extreme, abnormal and accidental action classes.
Note 2 to entry: Companion actions are of the same class as the principal action.
Note 3 to entry: Accompanying actions are of another class than the principal action.
3.45
recognized classification society
RCS
member of the international association of classification societies (IACS), with established rules and
procedures for classification and certification of floating structures used in energy activities, located at a
specific site, for an extended time period
3.46
reference period
time period used as a basis for determining the representative value (3.48) of operational, environmental,
accidental and/or repetitive actions (3.3)
3.47
reliability
performance (3.43) over a specified time period
Note 1 to entry: When reliability is used in the context of limit states, it can be expressed as the probability that the
limit is not exceeded.
ISO/DIS 19900:2025(en)
Note 2 to entry: The specified time period is typically one year.
3.48
representative value
value assigned to a basic variable (3.7) for limit state verification (3.37) in a design situation (3.18)
Note 1 to entry: Two types of representative value used in design verification are characteristic value and
...