ISO 19900:2019 石油および天然ガス産業—オフショア構造の一般要件 | ページ 6

3.1

abnormal environmental event

environmental hazardous event (3.27) having probability of occurrence not greater than 10⁻³ per annum (1 in 1 000 years)

3.2

accidental event

non-environmental hazardous event (3.27) having probability of occurrence not greater than 10⁻³ per annum (1 in 1 000 years)

Note 1 to entry: Accidental events, as referred to in this document, are associated with a substantial release of energy, such as vessel collisions, fires, and explosions.

Note 2 to entry: Lesser accidents that could be expected during the life of the structure, such as dropped objects and low energy vessel impact, are termed incidents and are addressed under operational design situations.

3.3

action

external load applied to the structure (3.53) (direct action) or an imposed deformation or acceleration (indirect action)

3.4

action effect

result of actions (3.3) on a structural component (3.49) (e.g. internal force, moment, stress, strain) or on the structure (3.53) (e.g. deflection, rotation)

3.5

air gap

distance between the highest water elevation and the lowest exposed part of the primary deck structure (3.53) not designed to withstand associated environmental action effects (3.4) for a defined return period (3.42)

Note 1 to entry: This definition can be refined for different platform types in their respective standards.

3.6

appurtenance

accessory or attachment to the structure (3.53) which typically assists installation, provides access or protection, or carries fluids or gas

Note 1 to entry: Appurtenances do not normally contribute to the stiffness of the structure but can attract significant hydrodynamic loading.

3.7

basic variable

variable representing physical quantities which characterize actions (3.3) and environmental influences, geometric quantities, or material properties including soil properties

Note 1 to entry: Basic variables are typically uncertain random variables or random processes used in the calculation or assessment of representative values of actions or resistance.

3.8

calibration

process used to determine and optimize partial factors using structural reliability analysis (3.52) and target reliabilities

3.9

characteristic value

value assigned to a basic variable (3.7) with a prescribed probability

Note 1 to entry: In some design/assessment situations, a variable can have two characteristic values, an upper value and a lower value.

3.10

conductor

tubular pipe set into the ground to provide the initial stable structural foundation for setting the surface casing and protecting the internal well string from metocean actions

Note 1 to entry: The conductor provides lateral and, in some cases, axial support, enables circulation of drilling fluid, and guides the drill string to facilitate setting of the surface casing.

3.11

decommissioning

process of shutting down a platform (3.37) enabling preparations for cleaning, dismantling and/or removal from location at the end of total service life (3.18)

3.12

design resistance

resistance limit calculated using factored representative values (3.40) of basic variables (3.7) or from factored expressions based on unfactored representative values (3.40) of basic variables (3.7)

3.13

design service life

planned period for which a structure (3.53) is used for its intended purpose with anticipated maintenance, but without substantial repair being necessary

3.14

design value

value derived from the representative value (3.40) for use in limit state verification (3.32)

Note 1 to entry: Design values can be different in different design/assessment situations due to different partial factors.

3.15

design/assessment criteria

quantitative formulations describing the conditions to be fulfilled for each design/assessment situation (3.16)

3.16

design/assessment situation

set of physical conditions for which the structure (3.53) or its components are verified

3.17

deterioration

process that adversely affects structural integrity (3.50) over time

Note 1 to entry: Deterioration can be caused by naturally occurring chemical, physical, or biological actions including corrosion, by severe environmental actions, by incidents and accidental actions, by repeated actions such as those causing fatigue, by wear due to use, and by improper operation and maintenance of the structure.

3.18

total service life

design service life (3.13) plus any subsequent operational life extension period(s)

3.19

durability

ability of a structure (3.53) or structural component (3.49) to maintain its function throughout its total service life (3.18)

3.20

exposure level

classification system used to establish relevant criteria for a structure (3.53) based on consequences of failure

3.21

extreme environmental event

environmental hazardous event (3.27) typically having probability of occurrence of 10⁻² per annum (1 in 100 years)

3.22

fit-for-service

fulfilling defined structural integrity (3.50) and performance (3.36) requirements

Note 1 to entry: A structure not meeting all the specific provisions can be fit-for-service, provided it does not cause unacceptable risk to life-safety or the environment.

3.23

fitness-for-service assessment

engineering evaluations to demonstrate that a structure (3.53) or a structural component (3.49) which deviates from its design basis, is fit-for-service (3.22)

Note 1 to entry: Deviations can include deterioration or damage, life extension, and other changes and modifications to the structure or to the design basis.

3.24

fixed structure

structure (3.53) that is bottom founded and transfers most of the actions (3.3) on it to the seabed (3.47)

3.25

floating structure

structure (3.53) where the full weight is supported by buoyancy

3.26

hazard

potential source of harm

Note 1 to entry: Harm is typically differentiated between harm to people, harm to the environment, or harm in terms of costs to organization(s) or society in general.

3.27

hazardous event

event which occurs when a hazard (3.26) interacts with a structure (3.53)

3.28

ice gouge

ice scour

incision in the seabed (3.47) or removal of seabed material by an ice feature

3.29

incident

non-environmental hazardous event (3.27) considered in an operational design/assessment situation (3.16)

Note 1 to entry: Incident, as referred to in this document, is a lesser accidental event, associated with possible local damage or damage to structural components, occurring with low probability, most typically associated with probabilities not less than 10⁻² per annum (1 in 100 years).

3.30

jack-up

mobile offshore unit with a buoyant hull and one or more legs that can be moved up and down relative to the hull

Note 1 to entry: A jack-up reaches its operational mode by lowering the leg(s) to the seabed and then raising the hull to the required elevation. The majority of jack-ups have three or more legs, each of which can be moved independently and which are supported in the seabed by spudcans.

3.31

limit state

state beyond which the structure (3.53) or structural component (3.49) no longer satisfies the design/assessment criteria (3.15)

3.32

limit state verification

demonstration that the total design action effect (3.4) in each design/assessment situation (3.16) does not exceed the limit state (3.31) design resistance (3.12)

3.33

nominal value

value assigned to a variable specified or determined on a non-statistical basis, typically from acquired experience or physical conditions, or as published in a recognized code or standard

Note 1 to entry: In some design/assessment situations, a variable can have two nominal values, an upper value and a lower value.

3.34

offshore

situated in water some distance from the shore

Note 1 to entry: Alternatively, near shore can be used to specify locations next to the coast or in mouths of rivers.

3.35

operator

representative of the company or companies leasing the site

Note 1 to entry: The operator is normally the oil company acting on behalf of co-licensees.

Note 2 to entry: The operator can be termed the owner or the duty holder.

3.36

performance

ability of a structure (3.53) or a structural component (3.49) to fulfil specified requirements

Note 1 to entry: Specified requirements include requirements for structural integrity and functionality.

3.37

platform

complete assembly of structural and non-structural systems for the purpose of development and production of petroleum and natural gas fields

Note 1 to entry: The platform includes the structure and non-structural systems such as topsides equipment, piping and accommodation.

Note 2 to entry: The platform includes the structural conductors and risers but does not include the non-structural components of the hydrocarbon wells.

Note 3 to entry: The platform does not include the geological strata supporting the foundation. However, site-specific geotechnical parameters provide the boundary conditions necessary to model the platform’s foundation or anchoring.

3.38

reference period

period of time used as a basis for determining the representative value (3.40) of operational, environmental, accidental and/or repetitive actions

3.39

reliability

performance (3.36) over a specified period of time

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.

Note 2 to entry: The specified period of time is typically one year.

3.40

representative value

value assigned to a basic variable (3.7) for verification of a limit state (3.31) in a design/assessment situation (3.16)

Note 1 to entry: Two types of representative value used in design verification are characteristic value and nominal value.

3.41

resistance

ability of a structure (3.53) , or a structural component (3.49) , to withstand action effects (3.4)

3.42

return period

average time between occurrences of an event

Note 1 to entry: The offshore industry commonly uses a return period measured in years for environmental events. The return period in years is equal to the reciprocal of the annual probability of occurrence of the event.

Note 2 to entry: For the purpose of this definition, events include both discrete hazardous events as well as exceedances of a threshold value of a relevant variable.

3.43

riser

part of an offshore pipeline, including any subsea spool pieces, which extends from the sea floor (3.46) to the pipeline termination point on a platform (3.37)

Note 1 to entry: For fixed structures, the termination point is usually the topsides.

Note 2 to entry: For floating structures, the riser can terminate at other locations on the platform.

3.44

robustness

ability of a structure (3.53) to withstand hazardous events (3.27) without being damaged to an extent disproportionate to the cause

3.45

scour

removal of seabed (3.47) material caused by currents and/or waves

3.46

sea floor

interface between sea and seabed (3.47)

3.47

seabed

materials below the sea floor (3.46)

3.48

splash zone

part of a structure (3.53) that is intermittently exposed to air and immersed in the sea

3.49

structural component

discrete part of a structure (3.53)

Note 1 to entry: For this document, a component can include an assembly of components, e.g. a subsystem.

3.50

structural integrity

ability of a structure (3.53) or a structural component (3.49) to maintain performance (3.36) throughout the total service life (3.18) , with respect to structural safety, robustness (3.44) , serviceability, and durability (3.19)

3.51

structural integrity management

SIM

systematic multi-step cyclic process intended to assure structural integrity (3.50) and functionality of a structure (3.53) throughout its total service life (3.18)

Note 1 to entry: Typical steps include data collection, data evaluation, development of an inspection strategy, development and execution of an inspection programme, and consequent remedial works.

3.52

structural reliability analysis

probabilistic methodology for determining limit state (3.31) failure probabilities

3.53

structure

combination of physically connected structural components (3.49)

3.54

topsides

structure (3.53) and equipment placed on a supporting structure [fixed or floating] to provide some or all of a platform’s (3.37) functions

Note 1 to entry: For a ship-shaped floating structure, the deck is not part of the topsides.

Note 2 to entry: For a jack-up, the hull is not part of the topsides.

Note 3 to entry: A separate fabricated deck or module support frame is part of the topsides.

3.55

ductility

<material> ability of a material to deform and absorb energy beyond its elastic limit

3.56

ductility

<structural component> ability of a structural component (3.49) to sustain action effects (3.4) beyond yield

3.57

ductility

<structural system> ability of a structural system to deform and dissipate energy, and to redistribute action effects (3.4)