Skip to content

Home > List of Keywords > *STIFFPRO

*STIFFPRO

Data format:

Two lines

IPRO ITYPE IEVOL IADD

If ITYPE = 1 Eso EIYZo GCTo ESe EIYZe GCTe

Or if ITYPE = 2 DEXTo THo DEXTe THe

Status : Optional

Purpose :

To define stiffener property

Details :

Parameter Description
IPRO property number
ITYPE Data type
* = 1 mechanical
* = 2 geometrical
IEVOL Type of evolution
IADD Define the resulting stiffness of the global system stiffener + pipe inside. This flag is useful for the STIFFENER type segments only since for TAPERED segment, the stiffener and the inside pipe may not be distinguished.
* = 0. The stiffener contribution is limited to the bending stiffness.
The system stiffener + pipe inside is given the properties of the pipe inside except for the bending stiffness which is the sum of both stiffness.
EA = EAriser
EI = EIriser + EIstiffener
GCt = GCtriser
* = 1. The stiffener imposes its stiffness to the whole structure. This option is actually used for TAPERED (see note)
* = 2 The stiffener contribution is added to the pipe for all the stiffnesses.
ESo axial stiffness at the beginning of the stiffener
EIYZo bending stiffness on y-axis or z-axis at the beginning
GCTo torsion stiffness at the beginning
ESe axial stiffness at the end of the stiffener
EIYZe bending stiffness on y-axis or z-axis at the end
GCTe torsion stiffness at the end
Or
DEXTo external diameter at the beginning of the stiffener
THo thickness at the beginning of the stiffener
DEXTe external diameter at the end of the stiffener
THe thickness at the end of the stiffener

Note

From conception phase, the STIFFENER segments defines a flexible pipe which has been given the stiffening structure. This is quite explicit in the panel where two boxes are used :

IADD offers several options to combine the stiffnesses of the flexible and the stiffnening structure. From users feed back, the following two options proved to be useful :

IADD = 0; The stiffener contribution is limited to the bending stiffness but the axial and torsion stiffness are those of the flexible pipe.

IADD = 2; The stiffener stiffnesses are added to the pipe.

On the contrary, for TAPERED segments, the pipe and the stiffening structure are nothing but the same pipe with a varying section.

Thats why, the panel TAPERED is quite similar to a RIGID pipe and no specific options are available about the combination of mechanical properties.

For both types STIIFENER or TAPERED, the same translation procedure into the input file (*.LOG) is used :

  1. An original inside property is created. This property is a flexible property in case of a STIFFENER segment and for a TAPERED segment, a virtual rigid property is created taking the smaller outside diameter;

  2. The stiffener property is translated defining the variation of diameter and thickness (*STIFFPRO);

  3. The stiffener is defined as a group of N elements associated with the inside property (*STIFFENER).

From this definition, the program automatically generates N new properties rooted from the original one but the following data are re-calculated with respect to the variation introduced by the stiffener :

For a conical variation, the Outside diameter (OD) and the thickness (WT) are taken at the middle of each element length (see figure below);

The mechanical properties are calculated according to the OD and WT according to the selected option for IADD;

For TAPERED : The internal cross section is defined for the whole stiffener segment whatever the couples (OD, WT) defined. For STIFFENER, the internal cross section of the flexible pipe is used.

In any case, the buoyancy diameter and the hydraulic diameter are imposed by the external diameter of the stiffening structure.

Note

N properties are then created as such :

  • if IADD = 1 : EA = EAstiffener

EI = EIstiffener

GCt = GCtstiffener