Glossary
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Water Depth
Definition(s)
Water Depth
vertical distance between the sea floor and still water level. NOTE 1 As there are several options for the still water level (see 3.35), there can be several water depth values. Generally, design water depth is determined to LAT or to mean sea level. NOTE 2 The water depth used for calculating wave kinematics varies between the maximum water depth of the highest astronomical tide plus a positive storm surge, and the minimum water depth of the lowest astronomical tide less a negative storm surge, where applicable. The same maximum and minimum water depths are applicable to bottom founded and floating structures, although water depth is usually a much less important parameter for floating structures. Water depth is, however, important for the design and analysis of the mooring system and risers for floating structures. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsWater Depth
Vertical distance between the sea floor and still water level. NOTE 1 As there are several options for the still water level (see A.6.4.4), there can be several water depth values. Generally, assessment water depth is determined to the extreme still water level. NOTE 2 The water depth used for calculating wave kinematics varies between the maximum water depth of the mean high water spring tide plus a positive storm surge, and the minimum water depth of the mean low water spring tide less a negative storm surge, where applicable. NOTE 3 Adapted from ISO 19901-1:2005, definition 3.41. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsVariable Load
Definition(s)
Variable Load
Items carried by the jack-up to support its operation that are not included in the fixed load. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsFoundation Utilization
Definition(s)
Foundation Utilization
Maximum value of the ratio of the generalized representation of the assessment action effect to the generalized representation of the assessment resistance in compatible units. NOTE 1 The utilization is the maximum absolute value of the ratio for each limit state and assessment situation being considered. NOTE 2 Only utilizations smaller than or equal to 1,0 satisfy the assessment criteria for a particular limit state. NOTE 3 The assessment action effect is the response to the factored actions. The assessment resistance is the representative resistance divided by the partial resistance factor. NOTE 4 For members and foundations subjected to combined forces, the internal force pattern and the resistance combine into an interaction equation. If the interaction equation governing the assessment check is, or can be, reduced to an inequality of the form U ≤ 1,0, then the utilization is equal to U. NOTE 5 Adapted from ISO 19902:2007, definition 3.56. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMember Utilization
Definition(s)
Member Utilization
Maximum value of the ratio of the generalized representation of the assessment action effect to the generalized representation of the assessment resistance in compatible units. NOTE 1 The utilization is the maximum absolute value of the ratio for each limit state and assessment situation being considered. NOTE 2 Only utilizations smaller than or equal to 1,0 satisfy the assessment criteria for a particular limit state. NOTE 3 The assessment action effect is the response to the factored actions. The assessment resistance is the representative resistance divided by the partial resistance factor. NOTE 4 For members and foundations subjected to combined forces, the internal force pattern and the resistance combine into an interaction equation. If the interaction equation governing the assessment check is, or can be, reduced to an inequality of the form U ≤ 1,0, then the utilization is equal to U. NOTE 5 Adapted from ISO 19902:2007, definition 3.56. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsUtilization
Definition(s)
Utilization
Maximum value of the ratio of the generalized representation of the assessment action effect to the generalized representation of the assessment resistance in compatible units. NOTE 1 The utilization is the maximum absolute value of the ratio for each limit state and assessment situation being considered. NOTE 2 Only utilizations smaller than or equal to 1,0 satisfy the assessment criteria for a particular limit state. NOTE 3 The assessment action effect is the response to the factored actions. The assessment resistance is the representative resistance divided by the partial resistance factor. NOTE 4 For members and foundations subjected to combined forces, the internal force pattern and the resistance combine into an interaction equation. If the interaction equation governing the assessment check is, or can be, reduced to an inequality of the form U≤1,0, then the utilization is equal to U. NOTE 5 Adapted from ISO 19902:2007, definition 3.56. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsUndrained Shear Strength
Definition(s)
Undrained Shear Strength
maximum shear stress or shear stress at a specified shear strain, in an undrained condition Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsUndrained Shear Strength
Maximum shear stress at yielding or at a specified maximum strain in an undrained condition. NOTE Yielding is the condition of a material in which a large plastic strain occurs at little or no stress increase. [ISO 19901-4:2003, definition 3.9]. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSustained Wind Speed
Definition(s)
Sustained Wind Speed
time-averaged wind speed with an averaging duration of 10 min or longer Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsSustained Wind Speed
Time-averaged wind speed with a defined averaging duration of 1 min or longer. NOTE Adapted from ISO 19901-1:2005, definition 3.37, which references a duration of “10 min or longer”. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSudden Cyclone
Definition(s)
Sudden Cyclone
Sudden tropical revolving storm that forms near the site and that can affect the jack-up before demanning can be completed within the time required by the emergency evacuation plan. NOTE The intent is that the jack-up be assessed to L1 for the specified sudden tropical revolving storm. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSudden Hurricane
Definition(s)
Sudden Hurricane
A hurricane that develops inside the Gulf of Mexico sufficiently close to the relevant platform such that personnel evacuation is not assured. Source: API RP 2SIM, Structural Integrity Management of Fixed Offshore Structures, First Edition, November 2014. Global StandardsSudden Hurricane
Sudden tropical revolving storm that forms near the site and that can affect the jack-up before demanning can be completed within the time required by the emergency evacuation plan. NOTE The intent is that the jack-up be assessed to L1 for the specified sudden tropical revolving storm. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSudden Typhoon
Definition(s)
Sudden Typhoon
Sudden tropical revolving storm that forms near the site and that can affect the jack-up before demanning can be completed within the time required by the emergency evacuation plan. NOTE The intent is that the jack-up be assessed to L1 for the specified sudden tropical revolving storm. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsStructural Analysis
Definition(s)
Structural Analysis
Process or algorithm for determining action effects from a given set of actions. NOTE 1 Structural analyses are performed at three levels [global analysis of an entire structure, analysis of part of a structure (e.g. a leg), local analysis of a structural member and local analysis of a structural component] using different structural models. NOTE 2 Adapted from ISO 19902:2007, definition 3.51. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsStochastic Analysis
Definition(s)
Stochastic Analysis
Analysis in which a probabilistic approach is taken to model the random nature of the variables of interest. NOTE In general, a linear(ized) stochastic analysis can be performed in the frequency domain or in the time domain, whereas non-linear stochastic analysis can only use time domain simulations. This part of ISO 19905 does not support frequency domain stochastic analysis. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSpudcan
Definition(s)
Spudcan
A large inverted cone that is roughly circular in-plan with a shallow conical underside and a sharp protruding spigot. It is mounted at the base of a jackup’s leg, and is primarily considered to provide sliding and bearing resistance to the jackup rig when deployed into the sea bed.
Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global StandardsSpudcan
Structure at the base of a leg supported by the soil. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSpectral Peak Period
Definition(s)
Spectral Peak Period
period of the maximum (peak) energy density in the spectrum NOTE In practice there is often more than one peak in a spectrum. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsSpectral Peak Period
Period of the maximum (peak) energy density in the spectrum. NOTE 1 In practice, there is often more than one peak in a spectrum. NOTE 2 There are two types of spectral peak period used within this part of ISO 19905: intrinsic and apparent. The distinction is discussed in A.7.3.3.5, which is, in turn, based on ISO 19901-1:2005, 8.3 and A.8.3. NOTE 3 Adapted from ISO 19901-1:2005, definition 3.32. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSpectrum
Definition(s)
Spectrum
Measure of the variance associated with a time-varying variable per unit frequency band and per unit directional sector. NOTE 1 Spectrum is a shorthand expression for the full and formal name of spectral density function or energy density function. NOTE 2 The spectral density function is the variance (the mean square) of the time-varying variable concerned in each frequency band and directional sector. Therefore, the spectrum is, in general, written with two arguments: one for the frequency variable and one for a direction variable. NOTE 3 Within ISO 19901-1, the concept of a spectrum applies to waves, wind turbulence and action effects (responses) that are caused by waves or wind turbulence. For waves, the spectrum is a measure of the energy traversing a given space. [ISO 19901-1:2005, definition 3.33]. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsEnergy Density Function
Definition(s)
Energy Density Function
Measure of the variance associated with a time-varying variable per unit frequency band and per unit directional sector. NOTE 1 Spectrum is a shorthand expression for the full and formal name of spectral density function or energy density function. NOTE 2 The spectral density function is the variance (the mean square) of the time-varying variable concerned in each frequency band and directional sector. Therefore, the spectrum is, in general, written with two arguments: one for the frequency variable and one for a direction variable. NOTE 3 Within ISO 19901-1, the concept of a spectrum applies to waves, wind turbulence and action effects (responses) that are caused by waves or wind turbulence. For waves, the spectrum is a measure of the energy traversing a given space. [ISO 19901-1:2005, definition 3.33]. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSpectral Density Function
Definition(s)
Spectral Density Function
Measure of the variance associated with a time-varying variable per unit frequency band and per unit directional sector. NOTE 1 Spectrum is a shorthand expression for the full and formal name of spectral density function or energy density function. NOTE 2 The spectral density function is the variance (the mean square) of the time-varying variable concerned in each frequency band and directional sector. Therefore, the spectrum is, in general, written with two arguments: one for the frequency variable and one for a direction variable. NOTE 3 Within ISO 19901-1, the concept of a spectrum applies to waves, wind turbulence and action effects (responses) that are caused by waves or wind turbulence. For waves, the spectrum is a measure of the energy traversing a given space.[ISO 19901-1:2005, definition 3.33]. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSpecial Survey
Definition(s)
Special Survey
Extensive and complete survey carried out at each nominal five year interval, which closes a cycle of annual classification and mandatory surveys. NOTE Also referred to as “renewal survey” by some IACS members. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSliding
Definition(s)
Sliding
Horizontal movement of a spudcan. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSlant-Leg Unit
Definition(s)
Slant-Leg Unit
Jack-up with legs that can be inclined at a significant angle to the vertical. NOTE The inclination angle is typically about 5°. The benefit is that the jack-up behaves more like a braced frame and less like a portal frame, with accompanying reductions in leg axial forces and moments. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSkirted Spudcan
Definition(s)
Skirted Spudcan
Spudcan with a peripheral skirt. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSignificant Wave Height
Definition(s)
Significant Wave Height
statistical measure of the height of waves in a sea state NOTE The significant wave height was originally defined as the mean height of the highest one-third of the zero upcrossing waves in a sea state. In most offshore data acquisition systems the significant wave height is currently taken as 4 m0 (where m0 is the zeroth spectral moment, see 3.31) or 4σ, where σ is the standard deviation of the time series of water surface elevation over the duration of the measurement, typically a period of approximately 30 min. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsSignificant Wave Height
Statistical measure of the height of waves in a sea state. NOTE The significant wave height was originally defined as the mean height of the highest one-third of the zero upcrossing waves in a sea state. In most offshore data acquisition systems, the significant wave height is currently taken as (where m0 is the zeroth spectral moment, see ISO 19901-1:2005, definition 3.31) or 4σ, where σ is the standard deviation of the time series of water surface elevation over the duration of the measurement, typically a period of approximately 30 min. [ISO 19901-1:2005, definition 3.30]. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSignificant Wave Height
average height of the highest third of prevailing waves, typically measured over a period of 3 hours . Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsShallow Gas
Definition(s)
Shallow Gas
Gas pockets or entrapped gas below impermeable layers at shallow depth. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsSea State
Definition(s)
Sea State
Condition of the sea during a period in which its statistics remain approximately constant. NOTE In a statistical sense the sea state does not change markedly within the period. The period during which this condition exists is usually assumed to be three hours, although it depends on the particular weather situation at any given time. [ISO 19901-1:2005, definition 3.26]. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsScatter Diagram
Definition(s)
Scatter Diagram
Joint probability of two or more (metocean) parameters. NOTE 1 A scatter diagram is especially used with wave parameters in the metocean context, see ISO 19901-1:2005, A.5.8. The wave scatter diagram is commonly understood to be the probability of the joint occurrence of the significant wave height (Hs) and a representative period (Tz,i or Tp,i). NOTE 2 Adapted from ISO 19901-1:2005, definition 3.24. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsRepresentative Value
Definition(s)
Representative Value
Value assigned to a basic variable for verification of a limit state. [ISO 19900:2002, definition 2.26]. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards Source: ISO 19900:2013, Petroleum and natural gas industries – General requirements for offshore structures. Global StandardsRPD
Definition(s)
RPD
The difference in elevations between the chords of any one leg.
Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global StandardsRPD
Rack Phase Difference. Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsRPD
Relative difference in the position of adjacent leg chords within a leg measured parallel to the longitudinal axis of the chords. NOTE This is the out-of-plane distortion of the plan-frame. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsRack Phase Difference
Definition(s)
Rack Phase Difference
The difference in elevations between the chords of any one leg.
Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global Standards