Pipe Section Data Inputs

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Pipe Section Data Inputs

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Overview

The Pipe Section component is divided into the following three tabs:

Properties tab

Attachments tab

SIFs tab

This article describes the inputs and dialogs that are available from these tabs.

Pipe Section – Properties Tab

pipe_section

Input

Description

Specification:

This drop-down list is used to select the format in which the pipe section properties are specified. The options are Standard (the default) and Direct.

The Standard format references a Material component, while the Direct format allows you to explicitly specify structural properties (e.g. bending stiffness) without any reference to a material.

Main Properties

Click on this button to display the Main Properties – Define dialog. This button is only available when you select Standard from the Specification Type drop-down list. See the ‘Main Properties – Define Dialog section in this article for a detailed description of this dialog.

External Coatings

Click on this button to display the External Coatings – Define dialog. This button is only available when you select Standard from the Specification Type drop-down list. See the ‘External and Internal Coatings – Define Dialog section in this article for a detailed description of this dialog.

Internal Coatings

Click on this button to display the Internal Coatings – Define dialog. This button is only available when you select Standard from the Specification Type drop-down list. See the ‘External and Internal Coatings – Define Dialog section in this article for a detailed description of this dialog.

Direct Properties

Click on this button to display the Properties – Direct dialog. This button is only available when you select Direct from the Specification Type drop-down list. See the ‘Properties – Direct Dialog’ section in this article for a detailed description of this dialog.

 

Main Properties – Define Dialog

main_properties_define

Input

Description

Weight in Air / Unit Length:

The weight in air or dry weight of the pipe section. This may be either a number or the word “CALCULATED”, and defaults to “CALCULATED”.

Both the Weight in Air/Unit Length and the Weight in Water/Unit Length for a pipe section contain the value “CALCULATED” by default. This means that both of these are computed internally using the values you specify for pipe section outer diameter, wall thickness, material mass density and seawater density but you can override this computation, and input both values directly here.

Units: [N/m] or [lb/ft]

Weight in Water / Unit Length:

The weight in water or submerged weight of the pipe section. This may be either a number or the word “CALCULATED”, and defaults to “CALCULATED”. See the description above for Weight in Air/Unit Length for more information.

Units: [N/m] or [lb/ft]

Outer Diameter:

The outer structural diameter of the pipe section.

Units: [mm] or [in]

Thickness:

The wall thickness of the pipe section.

Units: [mm] or [in]

Material:

A drop-down list that allows the selection of a Material component from all those already defined in the project.

Moment of Inertia:

The moment of inertia of the pipe section. This may be either a number or the word “CALCULATED”, and defaults to “CALCULATED”.

If moment of inertia contains the value “CALCULATED”, the value is computed internally using the values you specify for the pipe section outer diameter and wall thickness, but you can override this computation and input the value directly. See Note (b).

Units: [m4] or [ft4]

Drag Diameter:

The effective diameter for hydrodynamic force calculations for the pipe section. This input is optional, and may be either a number or “OD”, signifying the pipe outer diameter including any coatings. The input defaults to “OD”.  If the Drag Diameter for a Pipe Section is manually overwritten then the elevation of the section over supports in the Model component is changed accordingly.

Units: [mm] or [in]

Normal Drag:

The Morison’s Eq. drag coefficient for the direction normal to the section, denoted .

Normal Inertia:

The Morison’s Eq. inertia coefficient for the direction normal to the section, denoted .

Tangential Drag:

The Morison’s Eq. drag coefficient for the direction tangential to the section, denoted . This entry is optional, and if omitted defaults to zero.

Tangential Added Mass:

The Morison’s Eq. added mass coefficient in the direction tangential to the section, denoted . This entry is optional, and if omitted defaults to zero.

Normal Added Mass:

The Morison’s Eq. added mass coefficient in the direction normal to the section, denoted . This entry is optional, and if omitted defaults to .

Joint Length:

The total length of an individual pipe joint, comprising of the specified pipe section, including any uncoated ends. See Note (a).

Units: [m] or [ft]

Cut-Back Length:

The length of the uncoated cut-back at the end of an individual pipe joint comprising of the specified pipe section (e.g. in the vicinity of field joints). See Note (a).

Units: [m] or [ft]

Cut-Back Infill Density:

The mass density of the cut-back infill material. The thickness of the infill material is equal to the sum of all external coating layers. A Joint Length & Cut-Back Length must be specified before the material density is used in calculating the weight of the infill material.

Units: [kg/m3] or [slugs/ft3]

 

Notes:

(a)The Joint Length and Cut-Back Length specifications allow PipeLay to consider the portions of bare pipe at the ends of a pipe joint when calculating the pipe section weights per unit length. A coated length for a joint is determined as follows and it, in conjunction with an uncoated length, is used to calculate average values for the weights per unit length of the pipe joint/section. This calculation only takes effect when the Weight in Air/Unit Length and the Weight in Water/Unit Length inputs for the pipe section are set to “CALCULATED”.

 Coated Length = Joint Length – 2 x Cut-Back Length

(b)A user specified moment of inertia will change the bending & torsional response of the pipe section. If the selected Material is linear, the bending (EI) & torsional (GJ) stiffness terms for the pipe section are calculated using the user specified I value. If the selected material uses a non-linear Moment-Curvature curve, the moment values on the input curve are scaled by the ratio between the user-input moment of inertia and the calculated moment of inertia. If the selected material is a non-linear Ramberg-Osgood (RO) material, the value for My in the RO equation is calculated using the user specified I value.
                                       
In the case of a Stress/Strain non-linear material format the pipe section inner diameter is adjusted based on the user specified I value when generating the non-linear bending stiffness curve, details of this generation process can be found in Technical Note 7. Note that this diameter adjustment is for the pipe stiffness calculation only and the other aspects of the analysis, including results post-processing, are based on the actual pipe inner diameter.

 

External and Internal Coatings – Define Dialogs

internal_coatings_define

Specifying external and internal coatings for a pipe section allows you to model the presence of, for example, insulation material or marine fouling on the pipe section. You can specify as many external and internal coatings as necessary for any particular pipe section. The weight per unit length, contact diameter, drag diameter and buoyancy diameter of the pipe section are all modified to account for the presence of coatings. The order of coatings is consistent with the order in which they appear in the respective coatings dialog. In other words, coating number one is closest to the pipe. The Internal Coatings dialog is described below:

Input

Description

Coating Name:

The name of the pipe coating. You may specify as many coatings as are required to describe the pipe section, provided that each coating name is unique.

Thickness:

The thickness of the pipe coating.

Units: [mm] or [in]

Mass Density:

The mass density of the pipe coating.

Units: [kg/m3] or [slugs/ft3]

Water Absorption:

The percentage increase in mass of the coating due to water absorption.

Units: [%]

For an external coating, you also have the option to reference a Material component for the coating and to specify a Bond Bending Resistance for the coating layer interface. These inputs allow for the augmentation of the pipe stiffness to account for coating effects. Refer to Technical Note 7 for a detailed description of the stiffness augmentation process. The External Coatings dialog is shown below:

external_coatings_define

Note

The stiffening effect of external coatings is not captured in PipeLay Starter Edition

 

Input

Description

Coating Name:

The name of the pipe coating. You may specify as many coatings as are required to describe the pipe section, provided that each coating name is unique.

Thickness:

The thickness of the pipe coating.

Units: [mm] or [in]

Mass Density:

The mass density of the pipe coating. See Note (a).

Units: [kg/m3] or [slugs/ft3]

Water Absorption:

The percentage increase in mass of the coating due to water absorption.

Units: [%]

Water Absorption Volume:

The percentage of the coating volume that is fully saturated with water and so no longer contributes to the displaced volume for the pipe section. This input does not add any mass to the pipe section but rather reduces the buoyancy of the pipe section when it is submerged.

If an absorption volume is specified in conjunction with the Water Absorption input above then the Water Absorption value takes precedence and is used on its own without any effect from the Water Absorption Volume.

Units: [%]

Material

A drop-down list of all the Material components defined in the project. It is used to select the material whose mechanical properties are to be associated with this coating. The default is <none>, in which case no mechanical properties are associated with this coating. See Notes (b)-(d).

Bond Bending Resistance

The bond bending resistance of the coating. This entry is optional, and if omitted the bond between this coating and the next inner one is assumed to be perfect with no slippage possible. See Notes (e)-(g).

Units: [MPa] or [ksi]

 

Notes:

(a)The mass density specified in the coating dialog takes precedence over any mass density defined on an associated Material component, which is effectively ignored when it comes to coatings.

(a)Coating materials must either use a Linear or Non-Linear Stress/Strain definition. When a material is assigned to an external coating then the pipe section material itself must also have a Non-Linear Stress/Strain specification. These constraints are necessary in order to ensure an effective stiffness augmentation calculation.

(b)If this entry is omitted, then the coating affects only the weight and the contact/drag/buoyancy diameter of the pipeline.

(c)If a coating material has both compressive and tensile Stress/Strain properties then, in order for the compressive properties to be taken into account, the pipe section material must also have compressive and tensile properties specified.

(d)Only the Bond Bending Resistance entry for the outermost coating is taken into account. This means that slippage is considered only at the outermost coating. The other external coatings are assumed to remain in perfect bond with the pipe and each other.

(e)If a positive non-zero value is specified, then you need to reference a Material component.

(f)If no value is specified, then the bond is assumed to be perfect with no slippage accounted for.

 

Properties – Direct Dialog

properties_direct_define

 

Input

Description

Weight in Air / Unit Length:

The weight in air or dry weight of the pipe section.

Units: [N/m] or [lb/ft]

Bending Stiffness:

The bending stiffness of the pipe section.

Units: [kNm2] or [kips.ft2]

Axial Stiffness:

The axial stiffness of the pipe section.

Units: [kN] or [kips]

Torsional Stiffness:

The torsional stiffness of the pipe section.

Units: [kNm2 / radian] or [kips.ft2 / radian]

Outer Diameter:

The outer structural diameter of the pipe section.

Units: [mm] or [in]

Thickness:

The wall thickness of the pipe section.

Units: [mm] or [in]

Buoyancy Diameter:

The effective diameter for buoyancy force calculations for the pipe section. This input is optional, and may be either a number or “OD”, signifying the pipe section external diameter. The input defaults to “OD”.

Units: [mm] or [in]

Drag Diameter:

The effective diameter for hydrodynamic force calculations for the pipe section. This input is optional, and may be either a number or “OD”, signifying the pipe section external diameter. The input defaults to “OD”.

Units: [mm] or [in]

Normal Drag:

The Morison’s Eq. drag coefficient for the direction normal to the section, denoted .

Normal Inertia:

The Morison’s Eq. inertia coefficient for the direction normal to the section, denoted .

Tangential Drag:

The Morison’s Eq. drag coefficient for the direction tangential to the section, denoted . This entry is optional, and if omitted defaults to zero.

Tangential Added Mass:

The Morison’s Eq. added mass coefficient in the direction tangential to the section, denoted . This entry is optional, and if omitted defaults to zero.

Normal Added Mass:

The Morison’s Eq. added mass coefficient in the direction normal to the section, denoted . This entry is optional, and if omitted defaults to .

 

Pipe Section – Attachments Tab

attachmets_tab

Input

Description

Attachments:

This is a drop-down list that allows you to specify whether or not the pipe section is fitted with continuous buoyancy foam, buoyancy modules, and/or strakes.

The specification of attachments is only possible for Standard specification types, so this input, and the remaining inputs on the Attachments tab, are disabled when the selected Specification Type is Direct.

Buoyancy Continuous

Click on this button to display the Buoyancy Continuous – Define dialog. This button is only available when you select Buoyancy Continuous from the Attachments drop-down list. See the ‘Buoyancy Continuous – Define Dialog’ section in this article for a detailed description of this dialog.

Buoyancy Modules

Click on this button to display the Buoyancy Modules – Define dialog. This button is only available when you select Buoyancy Modular from the Attachments drop-down list. See the ‘Buoyancy Modules – Define Dialog section in this article for a detailed description of this dialog.

Strakes

Click on this button to display the Strakes – Define dialog. This button is only available when you select Strakes from the Attachments drop-down list. See the ‘Strakes – Define Dialog section in this article for a detailed description of this dialog.

 

Buoyancy Continuous – Define Dialog

buoyancy_continuous_define

Input

Description

Weight in Air / Unit Length:

The weight in air per unit length of the buoyancy material. This defaults to zero.

Units: [N/m] or [kips/ft]

Net Buoyancy / Unit Length:

The net buoyancy per unit length of the buoyancy material. This defaults to zero.

Units: [N/m] or [kips/ft]

 

Buoyancy Modules – Define Dialog

buoyancy_modules_define

Input

Description

Weight in Air of Module:

The weight in air of a single buoyancy module. This value defaults to zero.

Units: [kN] or [kips]

Net Buoyancy of Module:

The net buoyancy of a single buoyancy module. This value defaults to zero.

Units: [kN] or [kips]

Length:

The length of a single buoyancy module.

Units: [m] or [ft]

Centre to Centre Spacing:

The centre-to-centre spacing of the buoyancy modules along the pipe section.

Units: [m] or [ft]

 

Strakes – Define Dialog

strakes_define

Input

Description

Weight in Air / Unit Length:

The weight in air per unit length of the strakes. This value defaults to zero.

Units: [N/m] or [lb/ft]

Weight in Water / Unit Length:

The weight in water per unit length of the strakes. This defaults to zero.

Units: [N/m] or [lb/ft]

 

Pipe Section – SIFs Tab

Note

This tab is not available in PipeLay Starter Edition

 

You can use this tab to specify the Stress/Strain Intensity Factors (SIFs) of the pipe section for fatigue analysis. These factors are used to scale the bending stress or strain predictions along the pipe section during all types of postprocessing and fatigue analysis. Note that SIFs form part of the PipeLay model and so should be defined prior to running a full analysis. If SIFs are defined after the full analysis has been run then they may not take effect during subsequent postprocessing only runs.

sifs_tab

Input

Description

Constant

Click on this button to display the SIF Constant – Define dialog. See the ‘SIF Constant – Define Dialog section for more information about this dialog.

Variable

Click on this button to display the SIF Variable – Define dialog. See the ‘SIF Variable – Define Dialog section for more information about this dialog.

 

SIF Constant Dialog

sif_constant_define

Input

Description

Constant SIF:

The constant SIF value for the pipe section. PipeLay factors bending stresses and bending strains on the pipeline.

SIF Variable Dialog

sif_variable

Input

Description

Bending Strain:

The bending strain value that defines a point on the SIF relationship. You can specify as many bending strain values as necessary to define the relationship.

Units: [%]

Strain Intensity Factor:

The variable SIF value that corresponds to the bending strain value.