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*Geometric Sets |
 
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*Geometric Sets
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*Geometric Sets |
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To assign geometric properties to element sets.
Refer to Geometric Properties for further information on this feature.
A block of three lines, the first one of which is an optional line to specify the format in which the properties are input, which can be FLEXIBLE, RIGID or MOORING. This is followed by two lines defining the element properties. The block may be repeated to allow combinations of flexible riser, rigid riser and mooring line formats in one model.
A block of lines that make up the block when the format is for flexible risers:
[OPTION=FLEXIBLE]
SET=Set Name [, BUOYANCY=DISTRIBUTED] [, EIYY=Curve Name] [, EIZZ=Curve Name] [, GJ=Curve Name] [, EA=Curve Name] [, EI=Curve Name], [EI_HYSTERESIS=Curve Name]
[EIyy], [EIzz], [GJ], [EA], m, p, Di, Dd, Db [, Do, Dc]
[COMPRESSION CHECK=Check Setting]
A block of lines that make up the block when the format is for rigid risers with only elastic properties:
OPTION=RIGID
SET=Set Name [, BUOYANCY=DISTRIBUTED] [, E=Curve Name]
[E], G, Do, Di, rho [, A, I, J, Dd, Db, Dc]
[COMPRESSION CHECK=Check Setting]
A block of lines that make up the block when the format is for rigid risers with elastic-plastic properties:
OPTION=RIGID
SET=Set Name [, BUOYANCY=DISTRIBUTED], PLASTIC HARDENING=Plastic Hardening Model Name
E, G, Do, Di, rho [, A, I, J, Dd, Db, Dc]
[COMPRESSION CHECK=Check Setting]
A block of lines that make up the block when the format is for mooring lines:
[OPTION=MOORING]
SET=Set Name
EA, m, Do [, Dd, Db]
A block of lines that make up the block when the format is for truss elements:
[OPTION=TRUSS]
SET=Set Name [, EA=Curve Name]
[EA], m, Do [, Di, Dd, Db, Dc]
If the format option is not specified at all then it defaults to FLEXIBLE. If it is invoked for one set and then not specified explicitly for subsequent sets, then the specified format applies to the subsequent sets.
Where a non-linear material curve is specified on the SET= line, the corresponding numerical value on the next should be omitted. If a non-linear material curve name is specified for E, then the non-linear material curve must be defined in the *STRESS/STRAIN DIRECT keyword. If a non-linear material curve name is specified for any of the inputs EIyy, EIzz, GJ or EA, then the non-linear material curve must be defined in the *MOMENT-CURVATURE (EIyy & EIzz), *FORCE-STRAIN (EA) or *TORQUE-TWIST (GJ) keywords. If bending hysteresis is included in the model, you must use the *BENDING HYSTERESIS keyword. If a plastic hardening model name is specified, then this must be defined in the *PLASTIC HARDENING keyword.
For Flexible Riser format, the value for Do is only used when distributed buoyancy is selected. Also, the use of the EI=option precludes the use of both the EIyy=and EIzz=inputs.
Check Setting may be either AUTOMATIC (the default), NONE or a numeric value.
Input: |
Description |
Set Name: |
The element set to which the geometric properties are to be assigned. This defaults to all elements. |
Bending Stiffness: |
This option allows you to specify how the bending stiffness of the elements of the set is calculated, and is relevant to element sets whose bending stiffness is defined in terms of a non-linear material M-k curve or a non-linear hysteresis curve. The options are Linear (the default), Symmetric Non-Linear, Asmmetric Non-Linear and Hysteresis. See Note (b). |
EIyy: |
The bending stiffness about the local y-axis for the elements of the set or the name of a non-linear material stress/strain curve that defines this bending stiffness. See Note (c). |
EIzz: |
The bending stiffness about the local z-axis for the elements of the set or the name of a non-linear material stress/strain curve that defines this bending stiffness. See Note (c). |
GJ: |
The torsional stiffness for the elements of the set or the name of a non-linear material stress/strain curve that defines the torsional stiffness. See Notes (c) and (d). |
EA: |
The axial stiffness for the elements of the set or the name of a non-linear material stress/strain curve that defines the axial stiffness. See Note (c). |
m: |
The mass per unit length for the elements of the set. |
p: |
The polar inertia of cross section per unit length for the elements of the set. The units are mass by length. See Note (e). |
Di: |
The internal diameter of the elements of the set. This is used for computing the buoyancy contribution of the internal fluid, if there is any. The default is an internal diameter of 0. |
Dd: |
The drag diameter. This is the effective outer diameter for hydrodynamic force evaluation using Morison's Equation. |
Db: |
The buoyancy diameter. This is the effective outer diameter for buoyancy force calculations for the elements comprising the set. |
Do: |
The actual outer diameter of the elements of the set, not including additional external buoyancy material. This data is used only if the Distributed buoyancy option is invoked, or if any external coatings are applied. |
Dc: |
The effective diameter for contact calculations. This is relevant only when your Flexcom analysis includes guide surfaces or line clashing. See Note (g). |
Buoyancy: |
This option allows you to specify how the buoyancy forces experienced by the elements of the set are calculated. The options are Default and Distributed. See Note (f). |
Compression Check: |
Flexcom will issue a warning if the compressive load experienced in any element exceeds the critical Euler load. Refer to Compression and Buckling for further information. The options are Automatic (the default), Manual and None. If you opt for Manual, you must explicitly set a Compression Limit also. |
Compression Limit: |
A manually defined compression limit to be used in the Euler load check. |
(a)For a discussion of the different formats available to you to define geometric properties, and the program options for specifying non-linear material properties, refer to Geometric Properties in Flexible Riser Format.
(b)Generally speaking, you normally input the same non-linear relationship for EIyy and EIzz. In the program terminology, the Symmetric non-linear bending model involves the computation of a single bending stiffness EI at any solution time based on the total curvature k, with both EIyy and EIzz being set equal to EI. This means that the element stiffness will be same in any situation where k is the same, regardless of the values of the individual curvature components. An option to model Asymmetric non-linear bending behaviour is also provided. In this case, EIyy at any solution time is found from the curve you input for that stiffness term based on the instantaneous value of the corresponding local curvature term ky, and likewise EIzz is found based on instantaneous kz. This is true even if you input the same curve name for EIyy and EIzz. This can mean that bending response can differ for the same loading depending on element orientation; an orientation where ky and kz are non-zero can give a different response to an orientation with either ky or kz equal to zero.
(c)If a non-linear material curve name is specified for any of the inputs EIyy, EIzz, GJ or EA, then the non-linear material curve must be defined in the *MOMENT-CURVATURE (EIyy & EIzz), *FORCE-STRAIN (EA) or *TORQUE-TWIST (GJ) keywords. Note also that you may specify a combination of linear and non-linear material properties; for example, you might specify non-linear bending characteristics (EIyy and EIzz), and linear EA and GJ (that is, a single value for each of these).
(d)The units of torsional stiffness in Flexcom are [Force][Length**2]/[Radian].
(e)A discussion of the significance and calculation of the polar inertia per unit length term can be found in Mass and Polar Inertia per Unit Length.
(f)Flexcom provides two options for specifying how buoyancy forces generated by elements are determined; Default and Distributed. For the majority of analyses, the default buoyancy formulation provides the most realistic and accurate approach to modelling the buoyancy forces on the elements. Please refer to Buoyancy Formulations for a detailed description of both approaches.
(g)Contact diameter is relevant only when your Flexcom analysis includes guide surfaces or line clashing. Flexcom uses this input to determine when contact occurs. Note that this value is used only in contact calculations in the main Analysis module - it is not used by the clearance/interference postprocessing module Clear. Specification of a contact diameter is optional, and Dc defaults to the maximum of Dd, Db and Do if omitted.
(h)There are a number of different element diameters used by Flexcom. In the main Analysis module you can specify internal diameter, drag diameter, buoyancy diameter, outer diameter and contact diameter. In addition to these fundamental model inputs, you can specify separate internal and outer diameters for use in stress computations during postprocessing, and you can do this in either the main Analysis or Database Postprocessing modules. So it is conceivable that you could specify the outer diameter for a given element in three different places, and specify three different values if you so wish. Naturally, such a scenario can appear confusing, particularly for new users of the software. Refer to Diameter Inputs for a detailed discussion on the significance of each diameter input, in order to eliminate any possible ambiguity.
Input: |
Description |
Set Name: |
The element set to which the geometric properties are to be assigned. This defaults to all elements. |
E: |
The Young’s Modulus for the elements of the set or the name of a non-linear material stress/strain curve (see Note (e)). |
G: |
The Shear Modulus for the elements of the set. |
Do: |
The outer diameter of the elements of the set. This is used for computing the area, moment of inertia and polar moment of inertia of the elements, if these are not specified directly. It is also used as the default drag and buoyancy diameters. |
Di: |
The internal diameter of the elements of the set. This is also used for computing the area, moment of inertia and polar moment of inertia of the elements, if these are not specified directly. It is also used for computing the buoyancy contribution of the internal fluid, if there is any. The default internal diameter is zero, although this would normally be a positive value. |
rho: |
The mass density (mass per unit volume) of the material for the elements of the set. |
A: |
The cross-sectional area of the elements of the set. This entry is optional. See Note (c). |
I: |
The moment of inertia (second moment of area) of the elements of the set. This entry is optional. See Note (c). |
J: |
The polar moment of inertia of the elements of the set. This entry is optional. See Note (c). |
Dd: |
The drag diameter. This is the effective outer diameter for hydrodynamic force evaluation using Morison’s Equation. This entry is optional. The drag diameter defaults to the outer diameter Do. |
Db: |
The buoyancy diameter. This is the effective outer diameter for buoyancy force calculations for the elements comprising the set. This entry is optional. The buoyancy diameter defaults to the outer diameter Do. |
Dc: |
The effective diameter for contact calculations. This is relevant only when your Flexcom analysis includes guide surfaces or line clashing. See Note (f). |
Buoyancy: |
This option allows you to specify how the buoyancy forces experienced by the elements of the set are calculated. The options are Default and Distributed. See Note (d). |
Compression Check: |
Flexcom will issue a warning if the compressive load experienced in any element exceeds the critical Euler load. Refer to Compression and Buckling for further information. The options are Automatic (the default), Manual and None. If you opt for Manual, you must explicitly set a Compression Limit also. |
Compression Limit: |
A manually defined compression limit to be used in the Euler load check. |
(a)For a discussion of the different formats available to you to define geometric properties, and the program options for specifying non-linear material properties, refer to Geometric Properties in Rigid Riser Format.
(b)You must specify non-zero values for E, G and Do, and non-zero values for rho and Di would also be normal. E may be specified as a numerical value or defined in terms of a non-linear material stress/strain curve.
(c)If you do not specify values for A, I and J, Flexcom calculates them from Do and Di using the standard relations. You can specify values for one or two only of these three inputs and leave the others for Flexcom to calculate (for example, you might specify A only and let the program base I and J on Do and Di).
(d)Flexcom provides two options for specifying how buoyancy forces generated by elements are determined; Default and Distributed. For the majority of analyses, the default buoyancy formulation provides the most realistic and accurate approach to modelling the buoyancy forces on the elements. Please refer to Buoyancy Formulations for a detailed description of both approaches.
(e)If a non-linear material curve name is specified for E, then the non-linear material curve must be defined in the *STRESS/STRAIN DIRECT keyword.
(f)Contact diameter is relevant only when your Flexcom analysis includes guide surfaces or line clashing. Flexcom uses this input to determine when contact occurs. Note that this value is used only in contact calculations in the main Analysis module - it is not used by the clearance/interference postprocessing module Clear. Specification of a contact diameter is optional, and Dc defaults to the maximum of Dd, Db and Do if omitted.
(g)There are a number of different element diameters used by Flexcom. In the main Analysis module you can specify internal diameter, drag diameter, buoyancy diameter, outer diameter and contact diameter. In addition to these fundamental model inputs, you can specify separate internal and outer diameters for use in stress computations during postprocessing, and you can do this in either the main Analysis or Database Postprocessing modules. So it is conceivable that you could specify the outer diameter for a given element in three different places, and specify three different values if you so wish. Naturally, such a scenario can appear confusing, particularly for new users of the software. Refer to Diameter Inputs for a detailed discussion on the significance of each diameter input, in order to eliminate any possible ambiguity.
Input: |
Description |
Set Name: |
The element set to which the geometric properties are to be assigned. This defaults to all elements. |
Plastic Hardening: |
The name of the plastic hardening model associated with this element set. The plastic hardening model must be defined in the *PLASTIC HARDENING keyword. |
E: |
The Young’s Modulus for the elements of the set. |
G: |
The Shear Modulus for the elements of the set. See Note (b). |
Do: |
The outer diameter of the elements of the set. This is used for computing the area, moment of inertia and polar moment of inertia of the elements, if these are not specified directly. It is also used as the default drag and buoyancy diameters. |
Di: |
The internal diameter of the elements of the set. This is also used for computing the area, moment of inertia and polar moment of inertia of the elements, if these are not specified directly. It is also used for computing the buoyancy contribution of the internal fluid, if there is any. The default internal diameter is zero, although this would normally be a positive value. |
rho: |
The mass density (mass per unit volume) of the material for the elements of the set. |
A: |
The cross-sectional area of the elements of the set. This entry is optional. See Note (c). |
I: |
The moment of inertia (second moment of area) of the elements of the set. This entry is optional. See Note (c). |
J: |
The polar moment of inertia of the elements of the set. This entry is optional. See Note (c). |
Dd: |
The drag diameter. This is the effective outer diameter for hydrodynamic force evaluation using Morison’s Equation. This entry is optional. The drag diameter defaults to the outer diameter Do. |
Db: |
The buoyancy diameter. This is the effective outer diameter for buoyancy force calculations for the elements comprising the set. This entry is optional. The buoyancy diameter defaults to the outer diameter Do. |
Dc: |
The effective diameter for contact calculations. This is relevant only when your Flexcom analysis includes guide surfaces or line clashing. See Note (e). |
Buoyancy: |
This option allows you to specify how the buoyancy forces experienced by the elements of the set are calculated. The options are Default and Distributed. See Note (d). |
Compression Check: |
Flexcom will issue a warning if the compressive load experienced in any element exceeds the critical Euler load. Refer to Compression and Buckling for further information. The options are Automatic (the default), Manual and None. If you opt for Manual, you must explicitly set a Compression Limit also. |
Compression Limit: |
A manually defined compression limit to be used in the Euler load check. |
(a)For a discussion of the different formats available to you to define geometric properties, and the program options for specifying non-linear material properties, refer to Geometric Properties in Rigid Riser Format.
(b)You must specify non-zero values for E, G and Do, and non-zero values for rho and Di would also be normal. E may only be specified as a numerical value. The value of G will be overwritten to account for the Poisson's ratio.
(c)If you do not specify values for A, I and J, Flexcom calculates them from Do and Di using the standard relations. You can specify values for one or two only of these three inputs and leave the others for Flexcom to calculate (for example, you might specify A only and let the program base I and J on Do and Di).
(d)Flexcom provides two options for specifying how buoyancy forces generated by elements are determined; Default and Distributed. For the majority of analyses, the default buoyancy formulation provides the most realistic and accurate approach to modelling the buoyancy forces on the elements. Please refer to Buoyancy Formulations for a detailed description of both approaches.
(e)Contact diameter is relevant only when your Flexcom analysis includes guide surfaces or line clashing. Flexcom uses this input to determine when contact occurs. Note that this value is used only in contact calculations in the main Analysis module - it is not used by the clearance/interference postprocessing module Clear. Specification of a contact diameter is optional, and Dc defaults to the maximum of Dd, Db and Do if omitted.
(f)There are a number of different element diameters used by Flexcom. In the main Analysis module you can specify internal diameter, drag diameter, buoyancy diameter, outer diameter and contact diameter. In addition to these fundamental model inputs, you can specify separate internal and outer diameters for use in stress computations during postprocessing, and you can do this in either the main Analysis or Database Postprocessing modules. So it is conceivable that you could specify the outer diameter for a given element in three different places, and specify three different values if you so wish. Naturally, such a scenario can appear confusing, particularly for new users of the software. Refer to Diameter Inputs for a detailed discussion on the significance of each diameter input, in order to eliminate any possible ambiguity.
Input: |
Description |
Set Name: |
The element set to which the geometric properties are to be assigned. This defaults to all elements. |
EA: |
The axial stiffness for the elements of the set. |
m: |
The mass per unit length for the elements of the set. |
Do: |
The outer diameter of the elements of the set. |
Dd: |
The drag diameter. This is the effective outer diameter for hydrodynamic force evaluation using Morison's Equation. The drag diameter defaults to the outer diameter Do. |
Db: |
The buoyancy diameter. This is the effective outer diameter for buoyancy force calculations for the elements comprising the set. The buoyancy diameter defaults to the outer diameter Do. |
(a)For a discussion of different formats available to you to define geometric properties, and the program options for specifying non-linear material properties, refer to Geometric Properties in Mooring Line Format.
(b)There are a number of different element diameters used by Flexcom. In the main Analysis module you can specify outer diameter, drag diameter and buoyancy diameter. In addition to these fundamental model inputs, you can specify separate diameters for use in stress computations during postprocessing, and you can do this in either the main Analysis or Database Postprocessing modules. So it is conceivable that you could specify the outer diameter for a given element in three different places, and specify three different values if you so wish. Naturally, such a scenario can appear confusing, particularly for new users of the software. Refer to Diameter Inputs for a detailed discussion on the significance of each diameter input, in order to eliminate any possible ambiguity.
Input: |
Description |
Set Name: |
The element set to which the geometric properties are to be assigned. This defaults to all elements. |
EA: |
The axial stiffness for the elements of the set or the name of a non-linear material stress/strain curve that defines the axial stiffness. See Note (b). |
m: |
The mass per unit length for the elements of the set. |
Do: |
The outer diameter of the elements of the set. |
Di: |
The internal diameter of the elements of the set. This is used for computing the buoyancy contribution of the internal fluid, if there is any. The default is an internal diameter of 0. |
Dd: |
The drag diameter. This is the effective outer diameter for hydrodynamic force evaluation using Morison's Equation. The drag diameter defaults to the outer diameter Do. |
Db: |
The buoyancy diameter. This is the effective outer diameter for buoyancy force calculations for the elements comprising the set. The buoyancy diameter defaults to the outer diameter Do. |
Dc: |
The effective diameter for contact calculations. This is relevant only when your Flexcom analysis includes guide surfaces or line clashing. |
(a)For a discussion of different formats available to you to define geometric properties, and the program options for specifying non-linear material properties, refer to Geometric Properties for Truss Elements.
(b)Flexcom regards each set of truss elements defined under the *GEOMETRIC SETS keyword as a coherent structure. So it is important that you include a separate entry in the keyword for each discrete part of the model. For example, if you have a semi-submersible platform which is moored using a 3-line catenary system, then you should have 3 separate definitions of truss element properties under the *GEOMETRIC SETS keyword, even if all the material properties for each mooring line are identical. This helps to reduce the possibility of unnatural compression build up in truss elements, which can be an issue for severe environments. Refer to Compression in Truss Elements for further details.
(c)If a non-linear material curve name is specified for EA, then the non-linear material curve must be defined in the *FORCE-STRAIN keyword.
(d)Contact diameter is relevant only when your Flexcom analysis includes guide surfaces or line clashing. Flexcom uses this input to determine when contact occurs. Note that this value is used only in contact calculations in the main Analysis module - it is not used by the clearance/interference postprocessing module Clear. Specification of a contact diameter is optional, and Dc defaults to the maximum of Dd, Db and Do if omitted.
(e)There are a number of different element diameters used by Flexcom. In the main Analysis module you can specify outer diameter, drag diameter and buoyancy diameter. In addition to these fundamental model inputs, you can specify separate diameters for use in stress computations during postprocessing, and you can do this in either the main Analysis or Database Postprocessing modules. So it is conceivable that you could specify the outer diameter for a given element in three different places, and specify three different values if you so wish. Naturally, such a scenario can appear confusing, particularly for new users of the software. Refer to Geometric Properties for Truss Elements for a detailed discussion on the significance of each diameter input, in order to eliminate any possible ambiguity.