Petroleum and natural gas industries - Specific requirements for offshore structures - Part 2: Seismic design procedures and criteria (ISO 19901-2:2022)

This document contains requirements for defining the seismic design procedures and criteria for offshore structures; guidance on the requirements is included in Annex A. The requirements focus on fixed steel offshore structures and fixed concrete offshore structures. The effects of seismic events on floating structures and partially buoyant structures are briefly discussed. The site-specific assessment of jack-ups in elevated condition is only covered in this document to the extent that the requirements are applicable.
Only earthquake-induced ground motions are addressed in detail. Other geologically induced hazards such as liquefaction, slope instability, faults, tsunamis, mud volcanoes and shock waves are mentioned and briefly discussed.
The requirements are intended to reduce risks to persons, the environment, and assets to the lowest levels that are reasonably practicable. This intent is achieved by using:
a) seismic design procedures which are dependent on the exposure level of the offshore structure and the expected intensity of seismic events;
b) a two-level seismic design check in which the structure is designed to the ultimate limit state (ULS) for strength and stiffness and then checked to abnormal environmental events or the abnormal limit state (ALS) to ensure that it meets reserve strength and energy dissipation requirements.
Procedures and requirements for a site-specific probabilistic seismic hazard analysis (PSHA) are addressed for offshore structures in high seismic areas and/or with high exposure levels. However, a thorough explanation of PSHA procedures is not included.
Where a simplified design approach is allowed, worldwide offshore maps, which are included in Annex B, show the intensity of ground shaking corresponding to a return period of 1 000 years. In such cases, these maps can be used with corresponding scale factors to determine appropriate seismic actions for the design of a structure, unless more detailed information is available from local code or site-specific study.
NOTE      For design of fixed steel offshore structures, further specific requirements and recommended values of design parameters (e.g. partial action and resistance factors) are included in ISO 19902, while those for fixed concrete offshore structures are contained in ISO 19903. Seismic requirements for floating structures are contained in ISO 19904, for site-specific assessment of jack-ups and other MOUs in the ISO 19905 series, for arctic structures in ISO 19906 and for topsides structures in ISO 19901‑3.

Erdöl- und Erdgasindustrie – Spezielle Anforderungen für Offshore-Anlagen – Teil 2: Seismische Auslegungsverfahren und -kriterien (ISO 19901-2:2022)

Industries du pétrole et du gaz naturel - Exigences spécifiques relatives aux structures en mer - Partie 2: Procédures de conception sismique et critères (ISO 19901-2:2022)

Le présent document spécifie les exigences relatives à la définition des procédures et critères de conception parasismique pour les structures en mer; les recommandations concernant les exigences sont indiquées dans l'Annexe A. Les exigences portent sur les structures en mer fixes en acier et en béton. Les effets des événements sismiques sur les structures flottantes et partiellement flottantes sont brièvement décrits. L'évaluation, spécifique au site, des plates-formes auto-élévatrices en situation surélevée est uniquement traitée dans le présent document dans la mesure où les exigences sont applicables.
Seuls les mouvements du sol induits par des séismes sont traités en détail. D'autres risques géologiques tels que la liquéfaction, l'instabilité des pentes, les failles, les tsunamis, les volcans de boue et les ondes de choc sont également mentionnés et brièvement décrits.
Les exigences sont destinées à réduire les risques encourus par les personnes, l'environnement et les installations au niveau le plus bas qui soit raisonnablement réalisable. Ce résultat est obtenu à l'aide:
a) de procédures de conception parasismique qui dépendent du niveau d'exposition de la structure en mer et de l'intensité prévue des événements sismiques;
b) d'un contrôle de conception parasismique à deux niveaux, dans lequel la structure est conçue selon l'état limite ultime (ULS) en matière de résistance et de rigidité avant d'être vérifiée par rapport à des événements environnementaux anormaux ou à l'état limite anormal (ALS), afin de garantir qu'elle satisfait aux exigences de réserve de résistance et de dissipation d'énergie.
Les procédures et exigences s'appliquant à la réalisation d'une analyse probabiliste de l'aléa sismique (PSHA), spécifique au site, sont exposées pour les structures en mer installées dans des zones à forte activité sismique et/ou fortement exposées. Cependant, les procédures de l'étude PSHA ne sont pas expliquées de manière approfondie.
Lorsqu'une approche de conception simplifiée est admise, des cartes des eaux mondiales, incluses dans l'Annexe B, indiquent l'intensité des secousses du sol pour une période de retour de 1 000 ans. Dans de tels cas, ces cartes peuvent être utilisées avec les facteurs d'échelle correspondants pour déterminer les actions sismiques appropriées pour la conception d'une structure, sauf si des informations plus détaillées sont fournies par un code local ou une étude spécifique au site.
NOTE      Pour la conception des structures en mer fixes en acier, d'autres exigences spécifiques et des valeurs recommandées des paramètres de conception (par exemple: coefficients d'action et de résistance partiels) sont indiquées dans l'ISO 19902, tandis que celles relatives aux structures en mer fixes en béton sont énoncées dans l'ISO 19903. L'ISO 19904 intègre des exigences parasismiques relatives aux structures flottantes, la série ISO 19905 des exigences relatives à l'évaluation spécifique au site de plates-formes auto-élévatrices et autres MOU, l'ISO 19906 des exigences relatives aux structures arctiques et l'ISO 19901‑3 des exigences relatives aux superstructures.

Industrija za predelavo nafte in zemeljskega plina - Posebne zahteve za naftne ploščadi - 2. del: Postopki potresno varnega projektiranja in potresna merila (ISO 19901-2:2022)

General Information

Status
Published
Public Enquiry End Date
29-Apr-2020
Publication Date
18-Jul-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
13-Jul-2022
Due Date
17-Sep-2022
Completion Date
19-Jul-2022

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SLOVENSKI STANDARD
SIST EN ISO 19901-2:2022
01-september-2022
Nadomešča:
SIST EN ISO 19901-2:2018
Industrija za predelavo nafte in zemeljskega plina - Posebne zahteve za naftne

ploščadi - 2. del: Postopki potresno varnega projektiranja in potresna merila (ISO

19901-2:2022)

Petroleum and natural gas industries - Specific requirements for offshore structures -

Part 2: Seismic design procedures and criteria (ISO 19901-2:2022)

Erdöl- und Erdgasindustrie – Spezielle Anforderungen für Offshore-Anlagen – Teil 2:

Seismische Auslegungsverfahren und -kriterien (ISO 19901-2:2022)

Industries du pétrole et du gaz naturel - Exigences spécifiques relatives aux structures

en mer - Partie 2: Procédures de conception sismique et critères (ISO 19901-2:2022)

Ta slovenski standard je istoveten z: EN ISO 19901-2:2022
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
91.120.25 Zaščita pred potresi in Seismic and vibration
vibracijami protection
SIST EN ISO 19901-2:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 19901-2:2022
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SIST EN ISO 19901-2:2022
EN ISO 19901-2
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2022
EUROPÄISCHE NORM
ICS 75.180.10 Supersedes EN ISO 19901-2:2017
English Version
Petroleum and natural gas industries - Specific
requirements for offshore structures - Part 2: Seismic
design procedures and criteria (ISO 19901-2:2022)

Industries du pétrole et du gaz naturel - Exigences Erdöl- und Erdgasindustrie - Spezielle Anforderungen

spécifiques relatives aux structures en mer - Partie 2: für Offshore-Anlagen - Teil 2: Seismische

Procédures de conception sismique et critères (ISO Auslegungsverfahren und -kriterien (ISO 19901-

19901-2:2022) 2:2022)
This European Standard was approved by CEN on 12 June 2022.

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

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19901-2:2022 E

worldwide for CEN national Members.
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SIST EN ISO 19901-2:2022
EN ISO 19901-2:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 19901-2:2022
EN ISO 19901-2:2022 (E)
European foreword

This document (EN ISO 19901-2:2022) has been prepared by Technical Committee CEN/TC 67 "NA" 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 2023, and conflicting national standards shall

be withdrawn at the latest by January 2023.

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 19901-2:2017.

Any feedback and questions on this document should be directed to the users’ national standards

body/national committee. A complete listing of these bodies can be found on the CEN website.

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 19901-2:2022 has been approved by CEN as EN ISO 19901-2:2022 without any

modification.
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SIST EN ISO 19901-2:2022
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SIST EN ISO 19901-2:2022
INTERNATIONAL ISO
STANDARD 19901-2
Third edition
2022-06
Petroleum and natural gas
industries — Specific requirements
for offshore structures —
Part 2:
Seismic design procedures and
criteria
Industries du pétrole et du gaz naturel — Exigences spécifiques
relatives aux structures en mer —
Partie 2: Procédures de conception sismique et critères
Reference number
ISO 19901-2:2022(E)
© ISO 2022
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3  Terms and definitions .................................................................................................................................................................................... 2

4 Symbols and abbreviated terms..........................................................................................................................................................4

4.1 Symbols ......................................................................................................................................................................................................... 4

4.2 Abbreviated terms .............................................................................................................................................................................. 6

5  Earthquake hazards .........................................................................................................................................................................................6

6 Seismic design principles and methodology .......................................................................................................................... 7

6.1 Design principles .................................................................................................................................................................................. 7

6.2 Seismic design procedures .......................................................................................................................................................... 7

6.2.1 General ........................................................................................................................................................................................ 7

6.2.2 Extreme level earthquake design........................................................................................................................ 9

6.2.3 Abnormal level earthquake design .................................................................................................................... 9

6.3 Spectral acceleration data ......................................................................................................................................................... 10

6.4 Seismic risk category ..................................................................................................................................................................... 10

6.5 Seismic design requirements ................................................................................................................................................. 11

6.6 Site investigation ...............................................................................................................................................................................12

7  Simplified seismic action procedure ...........................................................................................................................................12

7.1 Soil classification and spectral shape .............................................................................................................................12

7.2 Seismic action procedure ........................................................................................................................................................... 16

8 Detailed seismic action procedure ................................................................................................................................................17

8.1 Site-specific seismic hazard assessment ...................................................................................................................... 17

8.2 Probabilistic seismic hazard analysis ............................................................................................................................. 17

8.3 Deterministic seismic hazard analysis .......................................................................................................................... 20

8.4 Seismic action procedure ........................................................................................................................................................... 20

8.5 Local site response analyses ...................................................................................................................................................23

9  Performance requirements ........................................................................................................................................... ........................24

9.1 ELE performance ............................................................................................................................................................................... 24

9.2 ALE performance............................................................................................................................................................................... 24

Annex A (informative) Additional information and guidance ..............................................................................................25

Annex B (informative) Simplified action procedure spectral accelerations .........................................................34

Annex C (informative) Regional information ..........................................................................................................................................47

Bibliography .............................................................................................................................................................................................................................52

iii
© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(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,

in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC

12, Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries,

in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 19901-2:2017), which has been

technically revised.
The main changes are as follows:
— the seismic hazard maps have been updated;
— Clause 3 has been updated.
A list of all parts in the ISO 19901 series can be found on the ISO website.

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 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)
Introduction

The International Standards on offshore structures prepared by TC 67 (i.e. ISO 19900, ISO 19902,

ISO 19903, ISO 19904 and ISO 19906) address design requirements and assessments of 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.

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 all offshore structural systems.

The International Standards on offshore structures prepared by TC 67 are 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.

The overall concept of structural integrity is described above. Some additional considerations apply for

seismic design. These include the magnitude and probability of seismic events, the use and importance

of the offshore structure, the robustness of the structure under consideration and the allowable damage

due to seismic actions with different probabilities. All of these, and any other relevant information,

need to be considered in relation to the overall reliability of the structure.

Seismic conditions vary widely around the world, and the design criteria depend primarily on

observations of historical seismic events together with consideration of seismotectonics. In many

cases, site-specific seismic hazard assessments will be required to complete the design or assessment

of a structure.

This document is intended to provide general seismic design procedures for different types of offshore

structures, and a framework for the derivation of seismic design criteria. Further requirements are

contained within the general requirements International Standard, ISO 19900, and within the structure-

specific International Standards, ISO 19902, ISO 19903, ISO 19904 and ISO 19906. The consideration of

seismic events in connection with mobile offshore units is addressed in the ISO 19905 series.

© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
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SIST EN ISO 19901-2:2022
INTERNATIONAL STANDARD ISO 19901-2:2022(E)
Petroleum and natural gas industries — Specific
requirements for offshore structures —
Part 2:
Seismic design procedures and criteria
1 Scope

This document contains requirements for defining the seismic design procedures and criteria for

offshore structures; guidance on the requirements is included in Annex A. The requirements focus on

fixed steel offshore structures and fixed concrete offshore structures. The effects of seismic events on

floating structures and partially buoyant structures are briefly discussed. The site-specific assessment

of jack-ups in elevated condition is only covered in this document to the extent that the requirements

are applicable.

Only earthquake-induced ground motions are addressed in detail. Other geologically induced hazards

such as liquefaction, slope instability, faults, tsunamis, mud volcanoes and shock waves are mentioned

and briefly discussed.

The requirements are intended to reduce risks to persons, the environment, and assets to the lowest

levels that are reasonably practicable. This intent is achieved by using:

a) seismic design procedures which are dependent on the exposure level of the offshore structure and

the expected intensity of seismic events;

b) a two-level seismic design check in which the structure is designed to the ultimate limit state (ULS)

for strength and stiffness and then checked to abnormal environmental events or the abnormal

limit state (ALS) to ensure that it meets reserve strength and energy dissipation requirements.

Procedures and requirements for a site-specific probabilistic seismic hazard analysis (PSHA) are

addressed for offshore structures in high seismic areas and/or with high exposure levels. However, a

thorough explanation of PSHA procedures is not included.

Where a simplified design approach is allowed, worldwide offshore maps, which are included in

Annex B, show the intensity of ground shaking corresponding to a return period of 1 000 years. In

such cases, these maps can be used with corresponding scale factors to determine appropriate seismic

actions for the design of a structure, unless more detailed information is available from local code or

site-specific study.

NOTE For design of fixed steel offshore structures, further specific requirements and recommended values

of design parameters (e.g. partial action and resistance factors) are included in ISO 19902, while those for fixed

concrete offshore structures are contained in ISO 19903. Seismic requirements for floating structures are

contained in ISO 19904, for site-specific assessment of jack-ups and other MOUs in the ISO 19905 series, for arctic

structures in ISO 19906 and for topsides structures in ISO 19901-3.
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 19900, Petroleum and natural gas industries — General requirements for offshore structures

© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)

ISO 19901-8, Petroleum and natural gas industries — Specific requirements for offshore structures –

Part 8: Marine soils Investigation

ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures

ISO 19903, Petroleum and natural gas industries — Concrete offshore structures
3  Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 19900 and the following apply.

ISO and IEC maintain terminology 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 level earthquake
ALE

intense earthquake of abnormal severity with a very low probability of occurring during the life of the

structure

Note 1 to entry: The ALE event is comparable to the abnormal event in the design of fixed structures that are

described in ISO 19902 and ISO 19903.
3.2
attenuation

decay of seismic waves as they travel from the earthquake source to the site under consideration

3.3
deaggregation

separation of seismic hazard contribution from different faults and seismic source zones

3.4
escape and evacuation system

system provided on the offshore structure to facilitate escape and evacuation in an emergency

EXAMPLE Passageways, chutes, ladders, life rafts and helidecks.
3.5
extreme level earthquake
ELE

strong earthquake with a reasonable probability of occurring during the life of the structure

Note 1 to entry: The ELE event is comparable to the extreme environmental event in the design of fixed structures

that are described in ISO 19902 and ISO 19903.
3.6
fault movement
movement occurring on a fault during an earthquake
3.7
ground motion

accelerations, velocities or displacements of the ground produced by seismic waves radiating away

from earthquake sources

Note 1 to entry: A fixed offshore structure is founded in or on the seabed (3.17) and consequently only seabed

motions are of significance. The expression "ground motions" is used rather than seabed motions for consistency

of terminology with seismic design for onshore structures.

Note 2 to entry: Ground motions can be at a specific depth or over a specific region within the seabed.

© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)
3.8
liquefaction

fluidity of soil due to the increase in pore pressures caused by earthquake action under undrained

conditions
3.9
modal combination
combination of response values associated with each dynamic mode of a structure
3.10
mud volcano

diapiric intrusion of plastic clay causing high pressure gas-water seepages which carry mud, fragments

of rock (and occasionally oil) to the surface

Note 1 to entry: The surface expression of a mud volcano is a cone of mud with continuous or intermittent gas

escaping through the mud.
3.11
probabilistic seismic hazard analysis
PSHA

framework permitting the identification, quantification and rational combination of uncertainties in

earthquakes' intensity, location, rate of recurrence and variations in ground motion (3.7) characteristics

3.12
probability of exceedance

probability that a variable (or that an event) exceeds a specified reference level given exposure time

EXAMPLE The annual probability of exceedance of a specified magnitude of ground acceleration, ground

velocity or ground displacement.
3.13
response spectrum

function representing the peak elastic response for single degree of freedom oscillators with a specific

damping ratios in terms of absolute acceleration, pseudo velocity, or relative displacement values

against natural frequency or period of the oscillators
3.14
safety system

systems provided on the offshore structure to detect, control and mitigate hazardous situations

EXAMPLE Gas detection, emergency shutdown, fire protection, and their control systems.

3.15
sea floor
interface between the sea and the seabed (3.17)
3.16
seabed slide
failure of seabed (3.17) slopes
3.17
seabed
soil material below the sea in which a structure is founded
3.18
seismic risk category
SRC

category defined from the exposure level and the expected intensity of seismic motions

© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)
3.19
seismic hazard curve

curve showing the annual probability of exceedance (3.12) against a measure of seismic intensity

Note 1 to entry: The seismic intensity measures can include parameters such as peak ground acceleration,

spectral acceleration (3.22), or spectral velocity (3.23).
3.20
seismic reserve capacity factor

factor indicating the structure’s ability to sustain ground motions due to earthquakes beyond the level

of the extreme level earthquake (3.5)

Note 1 to entry: The seismic reserve capacity factor is a structure specific property that is used to determine the

extreme level earthquake acceleration from the abnormal level earthquake (3.1) acceleration.

3.21
site response analysis

wave propagation analysis permitting the evaluation of the effect of local geological and soil conditions

on the ground motions (3.7) as they propagate up from depth to the surface at the site

3.22
spectral acceleration

maximum absolute acceleration response of a single degree of freedom oscillator subjected to ground

motions (3.7) due to an earthquake
3.23
spectral velocity

maximum pseudo velocity response of a single degree of freedom oscillator subjected to ground motions

(3.7) due to an earthquake

Note 1 to entry: The pseudo velocity spectrum is computed by factoring the displacement or acceleration spectra

by the oscillator’s circular frequency or the inverse of its frequency, respectively. The pseudo spectrum is either

relative or absolute, depending on the type of response spectra that is factored.

3.24
spectral displacement

maximum relative displacement response of a single degree of freedom oscillator subjected to ground

motions (3.7) due to an earthquake
3.25
static pushover analysis

application and incremental increase of a global static pattern of actions on a structure, including

equivalent dynamic inertial actions, until a global failure mechanism occurs
3.26
tsunami
long period sea waves caused by rapid vertical movements of the sea floor (3.15)

Note 1 to entry: The vertical movement of the sea floor is often associated with fault rupture during earthquakes

or with seabed slides (3.16).
4 Symbols and abbreviated terms
4.1 Symbols
a slope of the seismic hazard curve

C site coefficient, a correction factor applied to the acceleration part (shorter periods) of a

response spectrum
© ISO 2022 – All rights reserved
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SIST EN ISO 19901-2:2022
ISO 19901-2:2022(E)

C correction factor applied to the spectral acceleration to account for uncertainties not cap-

tured in a seismic hazard
...

SLOVENSKI STANDARD
oSIST prEN ISO 19901-2:2020
01-april-2020
Industrija za predelavo nafte in zemeljskega plina - Posebne zahteve za naftne
ploščadi - 2. del: Postopki potresno varnega projektiranja in potresna merila
(ISO/DIS 19901-2:2020)

Petroleum and natural gas industries - Specific requirements for offshore structures -

Part 2: Seismic design procedures and criteria (ISO/DIS 19901-2:2020)

Erdöl- und Erdgasindustrie - Spezielle Anforderungen für Offshore-Anlagen - Teil 2:

Seismische Auslegungsverfahren und -kriterien (ISO/DIS 19901-2:2020)

Industries du pétrole et du gaz naturel - Exigences spécifiques relatives aux structures

en mer - Partie 2: Procédures de conception et critères sismiques (ISO/DIS 19901-

2:2020)
Ta slovenski standard je istoveten z: prEN ISO 19901-2
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
91.120.25 Zaščita pred potresi in Seismic and vibration
vibracijami protection
oSIST prEN ISO 19901-2:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 19901-2:2020
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oSIST prEN ISO 19901-2:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 19901-2
ISO/TC 67/SC 7 Secretariat: BSI
Voting begins on: Voting terminates on:
2020-02-06 2020-04-30
Petroleum and natural gas industries — Specific
requirements for offshore structures —
Part 2:
Seismic design procedures and criteria

Industries du pétrole et du gaz naturel — Exigences spécifiques relatives aux structures en mer —

Partie 2: Procédures de conception et critères sismiques
ICS: 75.180.10
THIS DOCUMENT IS A DRAFT CIRCULATED
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ISO/DIS 19901-2:2020(E)
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oSIST prEN ISO 19901-2:2020
ISO/DIS 19901-2:2020(E)
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oSIST prEN ISO 19901-2:2020
ISO/DIS 19901-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................... v

Introduction ..................................................................................................................................................................... v

1 Scope ....................................................................................................................................................................1

2 Normative references ....................................................................................................................................1

3 Terms and definitions ....................................................................................................................................2

4 Symbols and abbreviated terms .................................................................................................................5

4.1 Symbols ...............................................................................................................................................................5

4.2 Abbreviated terms ..........................................................................................................................................6

5 Earthquake hazards ........................................................................................................................................7

6 Seismic design principles and methodology ..........................................................................................7

6.1 Design principles .............................................................................................................................................7

6.2 Seismic design procedures ...........................................................................................................................8

6.2.1 General ................................................................................................................................................................8

6.2.2 Extreme level earthquake design ..............................................................................................................9

6.2.3 Abnormal level earthquake design ........................................................................................................ 10

6.3 Spectral acceleration data ......................................................................................................................... 11

6.4 Seismic risk category ................................................................................................................................... 11

6.5 Seismic design requirements ................................................................................................................... 12

6.6 Site investigation .......................................................................................................................................... 13

7 Simplified seismic action procedure ..................................................................................................... 13

7.1 Soil classification and spectral shape .................................................................................................... 13

7.2 Seismic action procedure .......................................................................................................................... 17

8 Detailed seismic action procedure ......................................................................................................... 18

8.1 Site-specific seismic hazard assessment .............................................................................................. 18

8.2 Probabilistic seismic hazard analysis ................................................................................................... 18

8.3 Deterministic seismic hazard analysis ................................................................................................. 19

8.4 Seismic action procedure .......................................................................................................................... 20

8.5 Local site response analyses ..................................................................................................................... 23

9 Performance requirements ...................................................................................................................... 23

9.1 ELE performance ........................................................................................................................................... 23

9.2 ALE performance .......................................................................................................................................... 24

Annex A (informative) Additional information and guidance ................................................................... 26

A.1 Scope ................................................................................................................................................................. 26

A.2 Normative references ................................................................................................................................. 26

A.3 Terms and definitions ................................................................................................................................. 26

A.4 Symbols and abbreviated terms .............................................................................................................. 26

A.5 Earthquake hazards ..................................................................................................................................... 26

A.6 Seismic design principles and methodology ....................................................................................... 27

A.6.1 Design principles .......................................................................................................................................... 27

A.6.2 Seismic design procedures ........................................................................................................................ 27

A.6.3 Spectral acceleration data ......................................................................................................................... 28

A.6.4 Seismic risk category ................................................................................................................................... 29

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A.6.5 Seismic design requirements ................................................................................................................... 29

A.6.6 Site investigation .......................................................................................................................................... 29

A.7 Simplified seismic action procedure ..................................................................................................... 29

A.7.1 Soil classification and spectral shape ................................................................................................... 29

A.7.2 Seismic action procedure .......................................................................................................................... 30

A.8 Detailed seismic action procedure ........................................................................................................ 31

A.8.1 Site-specific seismic hazard assessment ............................................................................................. 31

A.8.2 Probabilistic seismic hazard analysis ................................................................................................... 31

A.8.3 Deterministic seismic hazard analysis ................................................................................................. 32

A.8.4 Seismic action procedure .......................................................................................................................... 32

A.8.5 Local site response analyses .................................................................................................................... 33

A.9 Performance requirements ...................................................................................................................... 34

Annex B (informative) Simplified action procedure spectral accelerations ....................................... 35

Annex C (informative) Regional information .................................................................................................. 50

C.1 General ............................................................................................................................................................. 50

C.2 Norway ............................................................................................................................................................. 50

C.2.1 Description of region .................................................................................................................................. 50

C.2.2 Technical requirements............................................................................................................................. 50

C.3 Canada .............................................................................................................................................................. 50

C.3.1 Description of region .................................................................................................................................. 50

C.3.2 Regulatory framework ............................................................................................................................... 50

C.3.3 Technical requirements............................................................................................................................. 51

Bibliography ................................................................................................................................................................. 53

© ISO 2020 – All rights reserved
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oSIST prEN ISO 19901-2:2020
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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 [or Project Committee] ISO/TC [or ISO/PC] ###,

[name of committee], Subcommittee SC ##, [name of subcommittee].

This second/third/… edition cancels and replaces the first/second/… edition (ISO #####:####), which

has been technically revised.
The main changes compared to the previous edition are as follows:
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A list of all parts in the ISO ##### series can be found on the ISO website.

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 2020 – All rights reserved
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oSIST prEN ISO 19901-2:2020
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Introduction

The series of International Standards applicable to types of offshore structure, ISO 19900 to ISO 19906, addresses

design requirements and assessments of 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 all

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.

The overall concept of structural integrity is described above. Some additional considerations apply for seismic

design. These include the magnitude and probability of seismic events, the use and importance of the offshore

structure, the robustness of the structure under consideration and the allowable damage due to seismic actions

with different probabilities. All of these, and any other relevant information, need to be considered in relation to the

overall reliability of the structure.

Seismic conditions vary widely around the world, and the design criteria depend primarily on observations of

historical seismic events together with consideration of seismotectonics. In many cases, site-specific seismic hazard

assessments will be required to complete the design or assessment of a structure.

This document is intended to provide general seismic design procedures for different types of offshore structures,

and a framework for the derivation of seismic design criteria. Further requirements are contained within the

general requirements standard, ISO 19900, and within the structure-specific standards, ISO 19902, ISO 19903,

ISO 19904 and ISO 19906. The consideration of seismic events in connection with mobile offshore units is

addressed in ISO 19905.

Some background to and guidance on the use of this document is provided in Annex A. The clause numbering in

Annex A is the same as in the normative text to facilitate cross-referencing.

Regional information on expected seismic accelerations for offshore areas is provided in Annex B.

© ISO 2020 – All rights reserved
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oSIST prEN ISO 19901-2:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 19901-2:2020(E)
Petroleum and natural gas industries — Specific requirements
for offshore structures — Part 2: Seismic design procedures
and criteria
1 Scope

This document contains requirements for defining the seismic design procedures and criteria for offshore

structures; guidance on the requirements is included in Annex A. The requirements focus on fixed steel offshore

structures and fixed concrete offshore structures. The effects of seismic events on floating structures and partially

buoyant structures are briefly discussed. The site-specific assessment of jack-ups in elevated condition is only

covered in this document to the extent that the requirements are applicable.

Only earthquake-induced ground motions are addressed in detail. Other geologically induced hazards such as

liquefaction, slope instability, faults, tsunamis, mud volcanoes and shock waves are mentioned and briefly

discussed.

The requirements are intended to reduce risks to persons, the environment, and assets to the lowest levels that are

reasonably practicable. This intent is achieved by using:

a) seismic design procedures which are dependent on the exposure level of the offshore structure and

the expected intensity of seismic events;

b) a two-level seismic design check in which the structure is designed to the ultimate limit state (ULS)

for strength and stiffness and then checked to abnormal environmental events or the abnormal limit

state (ALS) to ensure that it meets reserve strength and energy dissipation requirements.

Procedures and requirements for a site-specific probabilistic seismic hazard analysis (PSHA) are addressed for

offshore structures in high seismic areas and/or with high exposure levels. However, a thorough explanation of

PSHA procedures is not included.

Where a simplified design approach is allowed, worldwide offshore maps, which are included in Annex B, show the

intensity of ground shaking corresponding to a return period of 1 000 years. In such cases, these maps may be used

with corresponding scale factors to determine appropriate seismic actions for the design of a structure.

For design of fixed steel offshore structures, further specific requirements and recommended values of design

parameters (e.g. partial action and resistance factors) are included in ISO 19902, while those for fixed concrete

offshore structures are contained in ISO 19903. Seismic requirements for floating structures are contained in

ISO 19904, for site-specific assessment of jack-ups and other MOUs in ISO 19905 (all parts), for arctic structures in

ISO 19906 and for topsides structures in ISO 19901-3.
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 19900, Petroleum and natural gas industries — General requirements for offshore structures

ISO 19901-8, Petroleum and natural gas industries — Specific requirements for offshore structures –

Part 8: Marine soils Investigation

ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures

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ISO 19903, Petroleum and natural gas industries — Fixed concrete offshore structures

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 19900 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
abnormal level earthquake
ALE

intense earthquake of abnormal severity with a very low probability of occurring during the life of the

structure

Note 1 to entry: The ALE event is comparable to the abnormal event in the design of fixed structures which are

described in ISO 19902 and ISO 19903.
3.2
attenuation

decay of seismic waves as they travel from the earthquake source to the site under consideration

3.3
directional combination

combination of response values due to each of the three orthogonal components of earthquake-induced

ground motions
3.4
escape and evacuation system

system provided on the offshore structure to facilitate escape and evacuation in an emergency

EXAMPLE Passageways, chutes, ladders, life rafts and helidecks.
3.5
extreme level earthquake
ELE

strong earthquake with a reasonable probability of occurring during the life of the structure

Note 1 to entry: The ELE event is comparable to the extreme environmental event in the design of fixed structures

which are described in ISO 19902 and ISO 19903.
3.6
fault movement
movement occurring on a fault during an earthquake
3.7
ground motion

accelerations, velocities or displacements of the ground produced by seismic waves radiating away from

earthquake sources

Note 1 to entry A fixed offshore structure is founded in or on the seabed (3.17) and consequently only seabed

motions are of significance. The term ground motions is used rather than seabed motions for consistency of

terminology with seismic design for onshore structures.
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Note 2 to entry Ground motions can be at a specific depth or over a specific region within the seabed.

3.8
liquefaction

fluidity of soil due to the increase in pore pressures caused by earthquake action under undrained

conditions
3.9
modal combination
combination of response values associated with each dynamic mode of a structure
3.10
mud volcano

diapiric intrusion of plastic clay causing high pressure gas-water seepages which carry mud, fragments

of rock (and occasionally oil) to the surface

Note 1 to entry: The surface expression of a mud volcano is a cone of mud with continuous or intermittent gas

escaping through the mud.
3.11
probabilistic seismic hazard analysis
PSHA

framework permitting the identification, quantification and rational combination of uncertainties in

earthquakes' intensity, location, rate of recurrence and variations in ground motion (3.7) characteristics

3.12
probability of exceedance

probability that a variable (or that an event) exceeds a specified reference level given exposure time

EXAMPLE Example of probability of exceedance during a given exposure time is the annual probability of

exceedance of a specified magnitude of ground acceleration, ground velocity or ground displacement.

3.13
response spectrum

function representing the peak elastic response for single degree of freedom oscillators with a specific

damping ratios in terms of absolute acceleration, pseudo velocity, or relative displacement values against

natural frequency or period of the oscillators
3.14
safety system

systems provided on the offshore structure to detect, control and mitigate hazardous situations

EXAMPLE Gas detection, emergency shutdown, fire protection, and their control systems.

3.15
sea floor
interface between the sea and the seabed (3.17)
3.16
seabed slide
failure of seabed (3.17) slopes
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3.17
seabed
material below the sea floor (3.15) in which a structure is founded
3.18
seismic risk category
SRC

category defined from the exposure level and the expected intensity of seismic motions

3.19
seismic hazard curve

curve showing the annual probability of exceedance (3.12) against a measure of seismic intensity

Note 1 to entry: The seismic intensity measures can include parameters such as peak ground acceleration,

spectral acceleration (3.22), or spectral velocity (3.23).
3.20
seismic reserve capacity factor

factor indicating the structure’s ability to sustain ground motions due to earthquakes beyond the level of

the ELE (3.5)

Note 1 to entry: The seismic reserve capacity factor is a structure specific property that is used to determine the

ELE acceleration from the ALE (3.1) acceleration.
3.21
site response analysis

wave propagation analysis permitting the evaluation of the effect of local geological and soil conditions

on the ground motions (3.7) as they propagate up from depth to the surface at the site

3.22
spectral acceleration

maximum absolute acceleration response of a single degree of freedom oscillator subjected to ground

motions (3.7) due to an earthquake
3.23
spectral velocity

maximum pseudo velocity response of a single degree of freedom oscillator subjected to ground motions

(3.7) due to an earthquake

Note 1 to entry: The pseudo velocity spectrum is computed by factoring the displacement or acceleration spectra

by the oscillator’s circular frequency or the inverse of its frequency, respectively. The pseudo spectrum is either

relative or absolute, depending on the type of response spectra that is factored.

3.24
spectral displacement

maximum relative displacement response of a single degree of freedom oscillator subjected to ground

motions (3.7) due to an earthquake
3.25
static pushover method
static pushover analysis

application and incremental increase of a global static pattern of actions on a structure, including

equivalent dynamic inertial actions, until a global failure mechanism occurs
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3.26
tsunami
long period sea waves caused by rapid vertical movements of the sea floor (3.15)

Note 1 to entry: The vertical movement of the sea floor is often associated with fault rupture during earthquakes

or with seabed slides (3.16).
4 Symbols and abbreviated terms
4.1 Symbols
a slope of the seismic hazard curve
C site coefficient, a correcti
...

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