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*Properties |
 
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*Properties
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*Properties |
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To assign effective structural properties to element sets for use in calculating stresses.
Refer to Stress Properties for further information on this feature.
A block of two lines repeated as often as necessary. Each property specified on the second line can be omitted, in which case a default value will be used for stress calculations:
SET=Set Name
Do, Di, A, Iyy, Izz, Tmin
The properties specified here are used in calculating timetraces of stresses during an analysis, for use in subsequent Timetrace Postprocessing or Time Domain Fatigue Analysis. This keyword is optional and may be ignored if requested timetrace output does not include stresses, or if you wish to use the actual properties in the computation of stress timetraces. A similar keyword may be included in the Database Postprocessing keyword inputs, and if present, those properties will be used to compute stresses during database postprocessing. However, if the keyword is not included in the database postprocessing keyword file, the values specified here are carried through to the database postprocessor.
If any of the parameters A, Iyy, Izz or Tmin are omitted, default values are computed based on the specified (or default) values of Do and Di. The minimum wall thickness (Tmin) is only used in the alternative computation of von Mises stress, according to API-2RD.
Input: |
Description |
Set Name: |
The name of the element set to which the stress properties are to be assigned. This defaults to all elements. |
Do: |
The effective outside diameter for the elements of the set. The default depends on the format used to specify geometric data. If you used the Flexible Riser Format, then the default is the drag diameter for the elements of the set. If you used the Rigid Riser Format or Mooring Line Format, then Do here defaults to Do input in the properties data. See Note (a). |
Di: |
The effective internal diameter for the elements of the set. The default is the internal diameter specified in the geometric data. See Note (b). |
A: |
The effective cross-sectional area for the elements of the set. The default is given by:
where Do and Di are the inputs described above, default or otherwise. See Note (a). |
Iyy: |
The second moment of area about the local y-axis for the elements of the set. The default is given by:
where Do and Di are the inputs described above, default or otherwise. See Note (a). |
Izz: |
The second moment of area about the local z axis for the elements of the set. The default is Iyy above. |
Min. Wall Thickness: |
The minimum wall thickness for the elements of the set. The default is given by:
where Do and Di are the inputs described above, default or otherwise. See Note (e). |
(a)The purpose of this table is to input values to be used in calculating timetraces of stresses during an analysis, for use in subsequent Timetrace Postprocessing or Time Domain Fatigue Analysis. Among the parameters you can specify for timetrace output are hoop, bending, axial and von Mises stresses. To calculate these, the program requires inputs whose effective values may be different when used for calculating stresses than they are when calculating, for example, hydrostatic and hydrodynamic forces. For example, to calculate bending stress at the outer surface of the cross section, the effective outer diameter is required, and this can in general be different from either the drag or buoyancy diameters specified as part of the geometric data in Flexible Riser Format.
(b)You will recall that the internal diameter you specify is used only in calculating the effects of internal fluid when you use the Flexible Riser format. Therefore, if your structure has no internal fluid present, you can specify an internal diameter of zero as part of the geometric data. However, an effective internal diameter is required to calculate hoop and von Mises stresses, which is why an internal diameter option is provided in this table.
(c)Timetrace output from Flexcom is optional, and therefore so is this table. This table can also be ignored if you request timetrace output which does not include stresses (other outputs available include axial force, effective tension, bending moments, torques and shear forces).
(d)The other type of output produced by Flexcom is database output. Flexcom does not output stresses to the results database. If stresses are required, they are calculated by the Database Postprocessor. For this reason, the Database Postprocessor provides a table similar to this one to specify similar inputs. Therefore, if you propose to recover stresses from database output, you do not need to use this table. You may do so if you wish however, and any values specified here will carry through to the Database Postprocessor and be used there.
(e)The minimum wall thickness is only used in the computation of von Mises stress according to API-2RD. Refer to Von Mises Stress (API-2RD Method) for further details.
