Input to STAMOD
1. General Information
The input to the STAMOD MODULE
is divided into 3 main sections,
referred to as
Theoretical description of the static analysis procedures is given in
the chapters Static Catenary Analysis and Static Finite Element Analysis in the RIFLEX
Theory Manual. Guidance to static analysis is given in the Guidance to Static Analysis section of the Static Finite Element Analysis part of the RIFLEX
Theory Manual.
2. Static Analysis with Fixed Parameters and Parameter Variation
In static analysis with fixed parameters, loads types can be activated by the user specified input. For specification of the load types, see data group identifier LOAD GROUP DATA.
In static analysis with parameter variation, loads types are activated using the data group identifier Parameter VARIation DEFInition. The loads that can be activated by user specification are

Static offset variation

Current variation

Specified force variation

Bottom friction forces

Global and geotechnical springs

Material memory function

Boundary change
In addition, a set of load types are automatically activated using the data group identfier Parameter VARIation DEFInition. These loads types are

Volume forces

Tensioner forces

Roller contact forces

Initial stressed elements

Floater forces
Volume forces will be applied in DYNMOD if not activated by using the data group identifier
LOAD GROUP DATA.

If current, wind, floater forces and specified force are specified in STAMOD
but not activated using the data group identifier
LOAD GROUP DATA, current load, wind load, floater forces and
specified force will be applied in DYNMOD .

If not activated using the data group identifier LOAD GROUP DATA, inplane seafloor spring and friction contact will be activated in DYNMOD .

3. Data Group A: Control Information
This data group is mandatory for all types of analysis with STAMOD
.
3.1. Principal run parameters
3.1.1. Data group identifier, one input line
STAMod CONTrol INFOrmation CHVERS

CHVERS: character(8)
:RIFLEX
input file version, e.g. 3.6
3.1.2. Heading, three input lines
Identification of the run alphanumerical text. This text will be output
when running STAMOD
.
HEAD1 HEAD2 HEAD3

HEAD1: character
: Line 1 of heading text 
HEAD2: character
: Line 2 of heading text 
HEAD3: character
: Line 3 of heading text
Always 3 input lines which may all be blank
3.1.3. Options and print switches, one input line
IRUNCO IDRIS IANAL IPRDAT IPRCAT IPRFEM IPFORM IPRNOR IFILFM IFILCO

IRUNCO: integer, default: 0
: Run code for data check or executable run
IRUNCO = 0
: Data check run 
IRUNCO = 1
: Analysis run 
IRUNCO = 2
: Restart analysis. The data groupSpecification of restart run
must be given subsequent to this input line


IDRIS: character(6)
: Data set identifier corresponding to data for one riser system established byINPMOD

IANAL: integer
: Type of analysis to be performed
IANAL = 1
: Static analysis. Data group B must be provided for this analysis 
IANAL = 2
: Static analysis with parameter variation. Data groups B and C must be provided


IPRDAT: integer, default: 2
: Print switch for the amount of output from the data generation
IPRDAT=1
: Only identifiers and a few key data are printed 
IPRDAT>2
: Tabulated print of system and environmental data (recommended) 
IPRDAT=5
: Print of system presented by segment and print of environment data


IPRCAT: integer, default: 1
: Print switch for the amount of output from the catenary analysis
IPRCAT=1
: Gives print of final catenary solution 
IPRCAT=5
: Gives in addition print of stress free configuration 
IPRCAT=10
: Gives in addition print of the catenary iteration (for debug purposes)


IPRFEM: integer, default: 1
: Print switch for the amount of output fromFEM
analysis
IPRFEM=1
: Results are printed for the equilibrium configuration at the end of the final static load step. If the analysis includes parameter variation, results are also printed after the final parameter variation load step. 
IPRFEM=1
: AsIPRFEM=1
, but in addition roller contact forces are stored on files, see Riser type specification in INPMOD. Only available in standalone version ofRIFLEX
. 
IPRFEM=5
: Results are printed for equilibrium configurations at the end of each load group 
IPRFEM=10
: Results are printed for the equilibrium configurations at every load step


IPFORM: integer, default: 1
: Format for print ofFEM
results
IPFORM=1
: Debug format 
IPFORM=1
: Results are presented line by line. Moments and curvatures are given at both element ends 
IPFORM=2
: Results are presented line by line. Moments and curvatures are averaged at internal line nodes. Results at element ends are used at line ends (similar toOUTMO
processing) 
IPFORM=3
: Results are presented segment by segment. Moments and curvatures are averaged at internal segment nodes. Results at element ends are used at segment ends.


IPRNOR: integer, default: 1
: Print switch for convergence norms in staticFEM
analysis
IPRNOR=0
: No output of convergence norms 
IPRNOR=1
: Print of convergence norms


IFILFM: integer, default: 2
: Option for Matrix Plot file
IFILFM=0
: No print 
IFILFM
\(\mathrm {\neq }\)0
: Matrix Plot file named<prefix>_stamod.mpf
(IPRFEM
controls how often static key results are written to the Matrix Plot file)


IFILCO: integer, default: 0
: Print switch for storing system configuration to ascii files. Initial configuration used for FEanalysis and configurations after each loadgroup during the loading sequence are stored. The stored configurations may be used as start configuration for subsequentSTAFEM
analysis.
IFILCO=0
: No additional files 
IFILCO=1
:
Configurations stored to ASCii files:

<prefix>_configlg<i>
where the number<i>
indicates the load group number.


For configurations after parameter variation the files are named:

<prefix>_configlg<i><n>
where<n>
is the step number



Note that projection angles will only be printed to
<prefix>_stamod.res
for lines that consist of bar elements.
3.2. Specification of arclength calculation
This data group is optional.
This data group may be used to specify how the arclength coordinates are calculated. The arclength coordinates are used for result presentation, mainly on the .mpf files.
3.2.2. Options for arclength calculation, one input line
IOP_ARCLEN

IOP_ARCLEN: integer, default: 0
: option for arclength calculation for result presentation
IOP_ARCLEN = 0
: Accumulate arclength over all lines 
IOP_ARCLEN = 1
: Start at zero for each new line

Arclength coordinates were previously always accumulated over all
lines. This will continue to be the case if this data group is not
given or if IOP_ARCLEN = 0
is specified.
3.3. Specification of restart run
These input lines are only given for a restart run of STAMOD
(IRUNCO=2
in the previous data group, Options and print switches, one input line
), and should be given subsequent to
STAMOD CONTROL INFORMATION
.
Restart of STAMOD
makes it possible to continue computation from the
last successful load group.
A restart run of STAMOD
requires two data files from the previous run:

IFNDMP
which contains the entire work array 
IFNSTA
which contains the results to be processed byOUTMOD
During a run of STAMOD
, the entire work array (all data in core) can
be written to file IFNDMP
at the end of each completed load group.
This will be done if the data group STORE RESTART DATA is
specified.
The file is overwritten each time, so the content is always related to the last (successful) load group. Therefore a restart will normally start with the next load group. In case of restart from parameter variations, the analysis will continue with the next parameter variation step. This makes the parameter variation more flexible as the user can choose to vary one parameter at a time.
It is also possible to carry out several runs with parameter variations from the same static equilibrium configuration. The procedure to be used in this case is illustrated through the following example:

Run
STAMOD
in a normal way, (IANAL=1
) with the data group STORE RESTART DATA given. A file prefix of SA_ is inserted for the example. 
Make a copy of the files SA_IFNDMP.SAM and SA_IFNSTA.FFI to e.g. BACKUP.SAM and BACKUP.FFI, respectively.

Run restart with parameter variations, (
IANAL=2
). 
Now, a new restart can be made from the original static equilibrium configuration by copying BACKUP.SAM and BACKUP.FFI to SA_IFNDMP.SAM and SA_IFNSTA.FFI prior to execution.
The procedure with backup of files can easily be automated in a run command procedure.
Note that current must be present in the original run if restart with parameter variation of current data is specified. Otherwise, the original current will be loaded in the first parameters variation step.
RESTart PARAmeters STAMod
IDSTA

IDSTA: character(6)
: Identifier for original static analysis results
3.6. Export of element responses, one input line
This specification is optional. Specifying export of element responses
enables visualization of the incremental loading configurations by use
of the computer program SIMVIS
subsequent to static analysis. In
present version it is possible to specify element responses in form of
effective tension, resulting curvature and longitudinal stress (if
available).
STORe VISUalisation RESPonses
3.6.1. Detailed specification of exported element responses
This data group is optional.
By default effective tension for all lines will be exported. This input line makes it possible to limit or specify response types for selected lines in the system.
Number of input lines: as many as necessary.
OPTION CHRESP CHILIN

OPTION: character
:
= STORE

= NOSTORE


CHRESP: character
: Response type to be exported
= EFFAXFORCE
: Effective tension 
= RESCURV
: Resultant curvature 
= LONGSTRESS
: Longitudinal stress 
= ALL
: All of the above described responses


CHILIN: character
:
= LINEID
: Reference to line identifier 
= ALL
: All lines

3.7. Export of data for static restart, one input line
This specification is optional. If specified, the necessary data for a static restart will be stored on the _ifndmp.sam file at the end of each successfully completed static load group.
STORe RESTart DATA
3.8. Specification of FEM print
This data group is optional.
This data group may used to print FEM data to an Asciifile.
3.8.2. Options for FEM print, one input line
IOP_FEM_PRINT

IOP_FEM_PRINT: integer, default: 0
: option for print of FEM data to Asciifile
IOP_FEM_PRINT = 0
: No print of FEM data 
IOP_FEM_PRINT = 1
: Print of FEM data to file <prefix>_eledat.asc

The FEM data is stored for all beam and bar elements. For each element the following is stored in columns:

Line ID, local segment and element numbers, element end numbers

Coordinates of final static configuration

Arc length

Diameter and hydrodynamic diameter

Nondimensional drag coefficients

Current velocity in global x, y and xdirections
3.9. Specification of mass and inertia summary
This data group is optional.
This data group may be used to print a summary of mass, centre of mass, and mass moment of inertia for selected lines, in a user specified output reference system, to an Asciifile.
3.9.2. Type of output reference system, one input line
CHREF

CHREF: character(4)
: method for specifying output reference system
BODY
: Use a SIMO body coordinate system 
COOR
: User specified output coordinates

3.9.3. Specification of output reference system, one input line
The format of this input line depends on the value specified in the previous line:

Body coordinate system (i.e.
CHREF == BODY
)BODYID

BODYID: character(8)
: name of an existing SIMO body to use as output reference system


User specified output coordinates (i.e.
CHREF == COOR
)XPOS YPOS ZPOS ZROT

XPOS: real
: Xcoordinate of output reference frame, in global system, \(\mathrm {[L]}\) 
YPOS: real
: Ycoordinate of output reference frame, in global system, \(\mathrm {[L]}\) 
ZPOS: real
: Zcoordinate of output reference frame, in global system, \(\mathrm {[L]}\) 
ZROT: real
: rotation of the output reference frame about the global Zaxis, \(\mathrm {[deg]}\)

3.9.4. Load step configuration, one input line
CONFIG_STEP

CONFIG_STEP: character(4)
: load step where the summary is calculated in static analysis
CONFIG_STEP = INIT
: initial configuration 
CONFIG_STEP = FINA
: final static configuration

3.9.5. Number of lines and bodies included in summary, one input line
NLINES NBODIES

NLINES: integer
: number of lines to include in summary 
NBODIES: integer, default = 0
: number of bodies to include in summary
4. Data Group B: Static Analysis with Fixed Parameters
This section is mandatory, and the analysis must always be carried out before any type of dynamic analysis is started.
4.1. Definition of subsequent input
The below example specifies one nodal load, applies the 1st current profile and tells that wind is not used. Subsequent sections give further details.
'**********************************************************************
STATIC CONDITION INPUT
'**********************************************************************
'nlcomp icurin curfac iwindin
1 1 1.0 0
' static load components, units: kN/kNm
' lineid ilseg ilnode/ilelm ildof rlmag chicoo
shaft 2 1 4 1.0 LOCAL
'
' lcons = 1 : consistent load and mass formulation
' isolvr = 2 : sparse matrix storage
' lcons isolvr
1 2
4.1.2. External, static loads
NLCOMP ICURIN CURFAC IWINDIN

NLCOMP: integer, default: 0
: Number of additional load components. Loads to be specified in next data group,Additional, static load components', which is omitted if `NLCOMP=0
. 
ICURIN: integer, default: 0
: Current indicator
ICURIN = 0
: No current 
ICURIN = N
: Current profile no. N on referenced environmental description (IDENV
) is used. The profile may be scaled byCURFAC


CURFAC: integer, real: 1
: Scaling factor to amplify or reduce the referred current profile \(\mathrm {[1]}\) 
IWINDIN: integer, default: 0
: Wind indicator
IWINDIN = 0
: No wind 
IWINDIN = N
: Wind specification no. N on referenced environmental description (IDENV
) is used.

If current loads are applied in STAMOD
, the current active at the end
of the static analysis will be used in DYNMOD
. If current loads are
not applied in STAMOD
, the specified current profile ICURIN
will be
used in DYNMOD
with the scaling factor CURFAC
specified here.
CURFAC
must be 1.0 for a restart analysis.
4.1.3. Additional, static load components
This data specification is omitted if NLCOMP=0
. Otherwise NLCOMP
input lines are specified.
LINEID ILSEG ILNODE ILDOF RLMAG CHICOO

LINEID: character(8)
: Reference to line identifier. 
ILSEG: integer
: Segment number within the actual line. 
ILNODE: integer
: Local node (CHICOO=GLOBAL
) or element number (CHICOO=LOCAL
). 
ILDOF: integer
: Degree of freedom within the specified node/element.
ILDOF = 7….12
at end 2 of an element.


RLMAG: real, default: 0
: Magnitude of load component (F or FL). 
CHICOO: character(6), default: GLOBAL
: Reference system for application of nodal load components.
CHICOO = GLOBAL
: Force component refers to global system. The force is applied at the specified node. 
CHICOO = LOCAL
: Force component refers to local system. The force is applied to the specified element. 
If skew boundaries or vessel boundary are specified at the node
CHICOO=GLOBAL
means that the load component acts in the skew (vessel) system.

4.1.4. Load formulation and matrix format
LCONS ISOLVR

LCONS: integer, default: 0
: Switch for lumped or consistent load and mass formulation.
LCONS = 0
: Lumped load and mass formulation. 
LCONS = 1
: Consistent load and mass formulation. 
Applies also to DYNMOD


ISOLVR: integer, default: 1
: Matrix storage format. Applies also toDYNMOD
.
ISOLVR = 1
: Skyline, recommended for simple, single line riser models. 
ISOLVR = 2
: Sparse, recommended for coupled analysis and complex models with branch points. 
The free vibration option in
DYNMOD
requiresISOLVR = 1

When applying the lumped load and mass formulation (LCONS=0
), the
element nodes are assigned part of the distributed external element load
and mass directly. When using a consistent formulation (LCONS=1
), the
external element load and mass is distributed to the nodes using the
same interpolation (shape) functions as applied when determining the
element stiffness matrix. See the theory manual for more details.
The numerical solution speed for static and subsequent dynamic analysis
depends on the matrix storage format. For a typical single riser
analysis where the resulting stiffness matrix is rather narrow banded,
the skyline matrix storage method is the most efficient, ISOLVR=1
.
In case of many branch points, or when doing coupled analysis with many
mooring lines and/or risers connected to the same floating vessel, the
stiffness matrix may be significantly more broad banded. In such a case,
choosing sparse matrix storage may increase the numerical solution
speed, ISOLVR=2
.
Note: Since the difference in solution speed could be practically
negligible for small models, sparse matrix storage (ISOLVR=2
) may be a
good initial choice. Later, one could check if skyline matrix storage
gives better numerical performance.
4.2. Computational procedure selection
4.2.2. Method for static equilibrium computation
AMETH

AMETH: character(6)
: Code for computation method. The following options are available:
CAT
: Catenary analysis, bending stiffness neglected 
CATFEM
: Finite element method based on catenary start configuration 
STAFEM
: Finite element method based on start configuration read from file. 
FEM
: Finite element method based on stress free start configuration

Selection of options according to system type and whether a subsequent dynamic analysis is to be carried out or not:
4.3. Catenary analysis procedure, CAT
4.3.2. Parameters for catenary analysis
XL50 FL10 XU1TOL XU3TOL

XL50: real, default: see below
: Initial estimate of angle from vertical at the point where the catenary calculation starts \(\mathrm {[deg]}\) 
FL10: real, default: see below
: Initial estimate of axial force at the point where the catenary calculation starts \(\mathrm {[F]}\) 
XU1TOL: real, default: see below
: Tolerance of X1 coordinate at upper end \(\mathrm {[L]}\) 
XU3TOL: real, default: see below
: Tolerance of X3 coordinate at upper end \(\mathrm {[L]}\)
Default values will be computed for the standard riser system based on geometry and specified weights and forces, if the parameter is given a "slash"(/). For standard system SA, SB and SD the calculation of the catenary solution starts at the upper end, for SC it starts at the lower end.
For XL50
and FL10
default values are recommended. The values are
printed out on the result file. For the SC system these parameters are
dummy.
The default values of XU1TOL
and XU3TOL
are calculated as
\(\mathrm {10^{4}}\) (length of the riser).
4.4. Catenary and subsequent finite element analysis, CATFEM
4.4.2. Parameters for catenary equilibrium calculation
XL50 FL10 XU1TOL XU3TOL

XL50: real, default: see below
: Initial estimate of angle from vertical at the point where the catenary calculation starts \(\mathrm {[deg]}\) 
FL10: real, default: see below
: Initial estimate of axial force at the point where the catenary calculation starts \(\mathrm {[F]}\) 
XU1TOL: real, default: see below
: Tolerance of X1 coordinate at upper end \(\mathrm {[L]}\) 
XU3TOL: real, default: see below
: Tolerance of X3 coordinate at upper end \(\mathrm {[L]}\)
Default values will be computed for the standard riser system based on geometry and specified weights and forces, if the parameter is given a "slash"(/).
For standard system SA, SB and SD the calculation of the catenary solution starts at the upper end, for SC it starts at the lower end.
For XL50
and FL10
default values are recommended. The values are
printed out on the result file. For the SC system these parameters are
dummy.
The default values of XU1TOL
and XU3TOL
are calculated as
\(\mathrm {10^{4}}\) (length of the main riser line).
Next data group is Incremental loading procedure.
4.5. Finite element analysis from start configuration, STAFEM
Preliminary test version.
In present version it is assumed that the start solution represent a catenary solution.
4.5.2. Name of file containing the start solution
CHFSTA KFORM

CHFSTA: character(60)
: File name with specification of start configuration . The content of this file is described in Define Start Configuration. 
KFORM: integer, default: 1
: Code for file format
KFORM = 1
: Coordinates and base vector system given for all FEMnodes in increasing node number order.

Next data group is Incremental loading procedure.
4.7. Incremental loading procedure
This data group describes the incremental loading procedure from
catenary solution (CATFEM
), from a specified start solution (STAFEM
)
or from stress free configuration (FEM
) to the final static
equilibrium configuration.
A brief summary of the incremental loading procedure applied, is given
in the following. For a more detailed description including analysis
guidance, see Static Finite Element Analysis
in the RIFLEX Theory
Manual.
Based on load groups, the user is free to specify an arbitrary load sequence. Incrementation and iteration parameters are specified separately for each load group. One or several load types can be applied within each load group. Simultaneous application of several load types and userdefined order of the load application is therefore possible.
The incremental loading is normally carried out in the following sequence:

Load group 1: Volume forces (weight and buoyancy)

Load group 2: Specified displacements (i.e. displacements to final position of nodal points with specified boundary conditions)

Load group 3: Specified forces (nodal point loads)

Load group 4: Position dependent forces (current forces)
All userdefined load types have to be specified within a load group in order to be applied during the incremental loading of the system. Examples are roller and tensioner contact forces (elastic contact surface), initially stressed segments or floater forces.
The user may specify the load group for application of inplane seafloor friction and springs. It is also possible to neglect friction and springs in normal static analysis and activate friction during static parameter variation or at the start of dynamic analysis.
4.7.1. CATFEM analysis
Volume forces have to be applied within one incremental step in the
first specified load group. This is because volume forces and prescribed
translations from stress free to final positions of terminal points are
included in the catenary start solution. Deviations between the catenary
and the final FEM
solution are, however, present due to different
mathematical formulations and neglection of bending stiffness in the
catenary analysis. The first load group applying volume forces in one
incremental step, is therefore a simple equilibrium iteration starting
from the catenary solution with weight and buoyancy forces acting. The
equilibrium iteration may fail if there are significant differences
between the catenary solution and the final solution due to bending
stiffness. It is therefore possible to apply the bending stiffness in
several incremental steps to reach the final solution.
The iterative approach on boundary conditions used in the catenary analysis will give deviations between specified translating boundary conditions (i.e. x and z coordinates) and boundary condition computed by the catenary analysis. Further, specified boundary conditions for rotations at the supports will not be satisfied by the catenary analysis due to neglection of bending stiffness. A load group for prescribed displacements should therefore be included to account for inaccuracies in boundary conditions from the catenary analysis.
4.7.2. STAFEM analysis
The load types applied for the start configuration have to be indicated in the first specified load group. These load types will act with full force while the residual forces will be offloaded the specified number of load steps. The residual forces are the unbalanced forces based on the indicated load types and the internal forces that appear when the start configuration is described in the finite element formulation.
Note that it is assumed that final boundary conditions are included in the start configuration. As a consequence the procedure will be indifferent to specification of prescribed displacements.
4.7.3. Load group specification
The input lines Data group identifier…
, Load group incrementation…
and Load types to be activated…
have to be given in one block for each
load group.
Load group incrementation and iteration parameters, one input line
NSTEP MAXIT RACU CHNORM EACU

NSTEP: integer
: Number of load steps 
MAXIT: integer, default: 10
: Maximum number of iterations during application of load 
RACU: real, default:
\(\mathrm {10^{6}}\): Required accuracy measured by displacement norm \(\mathrm {[1]}\) 
CHNORM: character(4), default: DISP
: Convergence norm switch
= DISP
: Use the default Euclidean displacement norm only 
= BOTH
: Use both the default Euclidean displacement norm and the energy norm


EACU: real, default:
\(\mathrm {10^{6}}\): Required accuracy measured by energy norm
Dummy if
CHNORM=DISP

Load types to be activated, one line for each load type to be activated within the load group
LOTYPE ISPEC

LOTYPE: character(4)
: Load type to be applied
= VOLU
: Volume forces 
= DISP
: Specified displacements 
= SFOR
: Specified forces 
= CURR
: Current forces 
= TENS
: Activate tensioner contact forces 
= ROLL
: Activate roller and tubular contact forces 
= PIPE
: Activate pipeinpipe contact forces 
= ISTR
: Initially prestressed segments 
= FLOA
: Floater forces 
= FRIC
: Activate bottom friction forces 
= SPRI
: Activate global and geotechnical springs 
= BEND
: Bending stiffness 
= TEMP
: Temperature variation 
= PRES
: Pressure variation 
= MEMO
: Activate material memory formulation (Isotropic/kinematic hardening) 
= BOUN
: Activate boundary change 
= WINC
: Run winch(es) 
= GROW
: Apply crosssection changes from growth profile 
= WIND
: Wind forces


ISPEC: integer
: Parameter used for further description of applied load type:
LOTYPE = PIPE
:
ISPEC = 0
(default): Possible pipeinpipe contact enabled (ENTERED) 
= 1
: Specify start condition for pipeinpipe contact


LOTYPE = TEMP
:
ISPEC = NLSPEC
: Number of subsequent input lines for specification of temperature variation.


LOTYPE = PRES
;
ISPEC = Nxxx
: Number of subsequent input lines for specification of pressure variation


LOTYPE = BOUN
:
ISPEC = NBOUND
: Number of nodes with change in boundary conditions.


LOTYPE = WINC
:
ISPEC = Nxxx
: Number of subsequent input lines for specification of winch run


LOTYPE = GROW
:
ISPEC = 0
(default): No scaling of growth profile. 
ISPEC = 1
: Number of subsequent input lines for specification of growth scaling.


LOTYPE = WIND
:
ISPEC = 0
(default): No wind on turbine blades 
ISPEC = 1
: Number of subsequent input lines for specification of wind on turbine blades.


ISPEC
is dummy for other load types

Some static loads will be incremented over NSTEP load steps
while others will be activated at the beginning of the load group. For
example volume forces and current forces are incremented over the
specified load steps while element memory and contact forces are
activated at the beginning of the load group in which they are
specified.

Volume forces have to be applied in the first specified load group in
case of CATFEM
or STAFEM
analysis. For CATFEM
analysis the number
of load steps in this load group has to be one (NSTEP = 1
).
The initial elongation of fibre rope segments is applied in the same
way as userdefined stressfree segment lengths, i. e. gradually
during a static load group. If ISTR Initially prestressed segments
is specified, the fibre rope elongation will be applied in this load
group together with any stressfree segment lengths specified by the
user. Otherwise, the elongation will be automatically applied in the
first load group.
Pipeinpipe contact; One input line given if LOTYPE=PIPE and ISPEC = 1
CHPCNT

CHPCNT: character
:
= ENTERED

= NOT ENTERED

ENTERED should be used for analysis of slender structures
such as risers, cables and umbilicals. NOT ENTERED is intended to be
used for marine operations.

The master and slave pipe in static free condition should be modelled as close to the final configuration as
possible, see illustration in the figures Example: pipeinpipe
modelled
as ENTERED
and Example: pipeinpipe
modelled as NOT ENTERED
below.
ENTERED
NOT ENTERED
Temperature variation, NLSPEC input lines only given if LOTYPE = TEMP
LINEID ISEG IEC TEMP

LINEID: character(8)
: Reference to line identifier 
ISEG: integer/character
: Segment number
= 0
/ "ALL": All segments in specified line


IEL: integer/character
: Element number
= 0
/ "ALL": All elements in specified line


Temp: real
: Temperature at end of temperature variation
The temperature is varied linearly during the load group from the
starting temperature given in the crosssectional data in INPMOD
and
ending with the temperature specified here.
A linear variation of temperature over a sequence of elements may be specified by giving a negative element number at the second end of the linear variation
Pressure variation, NLSPEC input lines if LOTYPE = PRES
MRLID PRESSI DPRESS VVELI

MRLID: character(8)
: Reference to Main Riser Line identifier 
PRESSI: real, default: 0
: Final pressure at inlet end \(\mathrm {[F/L^2]}\) 
DPRESS: real, default: 0
: Final pressure drop \(\mathrm {[F/L^3]}\) 
VVELI: real, default: 0
: Final fluid velocity \(\mathrm {[L^3/T]}\)
Dummy in present version

Boundary changes, 2 x NBOUND input lines if LOTYPE = BOUN
Identification of node for boundary change .
IREFID ILSEG ILNODE IOP

IREFID: character(8)
: Reference to line or supernode identifier. 
ILSEG: integer
:
If
IREFID
refers to a line,ILSEG
is the segment number within this line 
If
IREFID
refers to a supernode,ILSEG
must be zero


ILNODE: integer
:
If
IREFID
refers to a line,ILNODE
is the node number within segmentILSEG

If
IREFID
refers to a supernode,ILNODE
must be zero


IOP: integer
: Parameter for boundary change option
= 0
: Boundary conditions: fixed, prescribed or free 
= 1
: Boundary conditions: rigid node connection (The node will become a slave node.)

Ordinary (line end) supernodes and SIMO body nodes with
CHLOCA_OPT=POSI
may have boundary change.
Status for nodal degrees of freedom. To be given if IOP = 0
IPOS IX IY IZ IRX IRY IRZ

IPOS: integer
: Boundary condition type
IPOS = 0
: The node is fixed in global system 
IPOS = N
: The node is attached to support vessel no N


IX: integer
: Boundary condition code for translation in Xdirection
IX = 0
: Free 
IX = 1
: Fixed of prescribed


IY: integer
: Boundary condition code for translation in Ydirection
Same interpretation as for
IX
.


IZ: integer
: Boundary condition code for translation in Zdirection
Same interpretation as for
IX
.


IRX: integer
: Boundary condition code for rotation around Xdirection
Same interpretation as for
IX
.


IRY: integer
: Boundary condition code for rotation around Ydirection
Same interpretation as for
IX
.


IRZ: integer
: Boundary condition code for rotation around Zdirection
Same interpretation as for
IX
.

Identification of master node. To be given if IOP = 1
LINEID ILSEG ILNODE

LINEID: character(8)
: Reference to line identifier 
ILSEG: integer
: Segment number within the actual line 
ILNODE: integer
: Local node number within segment
Winch run, NLSPEC input lines only given if LOTYPE = WINC
IWINCH WILNG

IWINCH: integer
: Line number 
WILNG: real
: Total run length \(\mathrm {[L]}\)
WILNG > 0
: winching out, i.e. the winch run will increase the active
length.
Growth profile, ISPEC=1 input lines only given if LOTYPE = GROW
GFAC

GFAC: real, default: 1.0
: Scaling of growth profile
Wind force, ISPEC=1 input lines only given if LOTYPE = WIND
WindOnTurbineBlades

WindOnTurbineBlades: character(8), default: OFF
: Code for wid loads on turbine blades
WindOnTurbineBlades = OFF
: No wind loads on turbine blades in static analysis. 
WindOnTurbineBlades = ON
: Wind loads on turbine blades in static analysis.

Note that wind loads will be applied on turbine blades and the rest of the structure in dynamic analysis.
4.8. Define stressfree configuration
This data group is optionally available for AR systems. It enables the user to define an arbitrary stressfree configuration without having to establish a complex line/supernode system model. The option is useful for effective modelling of prebent sections.
This data group will redefine the stressfree configuration, but will not
affect the coordinates for static equilibrium position given as input to
INPMOD
, data group
Specification of boundary conditions, stressfree configuration and static equilibrium configuration.
4.8.2. File name
CHFCON

CHFCON: character(80)
: File name with definition of stress free configuration
4.8.3. File format
KFORM

KFORM: integer, default: 1
: Code for file format
KFORM = 1
: Stress free coordinates given for allFEM
nodes in increasing node number order. The content of this file is described in Section 7.1.1

4.9. Bottom geometry file
This data group is given if IBOT 3D = 1
in the INPMOD
input file,
and allows the user to define an uneven seabed, using depth data in a
regular grid with equidistant spacing.
4.9.2. File name
CHFBOT

CHFBOT: character(80)
: File name with seabed geometry data
The content of this file is described in Define uneven seabed geometry.
4.9.3. Coordinates of the seabed file reference system
XOS YOS ZOS ANGOS

XOS: real, default: 0
: xcoordinate of the origin of the seabed file reference system, in the global reference system, see Seabed reference system to global coordinates. \(\mathrm {[L]}\) 
YOS: real, default: 0
: ycoordinate of the origin of the seabed file reference system, in the global reference system, see Seabed reference system to global coordinates. \(\mathrm {[L]}\) 
ZOS: real, default: 0
: zcoordinate of the origin of the seabed file reference system, in the global reference system, see Seabed reference system to global coordinates in zdirection. \(\mathrm {[L]}\) 
ANGOS: real, default: 0
: Angle between the xaxis of the seabed file reference system and the xaxis of the global reference system (positive anticlockwise), see Seabed reference system to global coordinates. \(\mathrm {[deg]}\)
5. Data Group C: Static Analysis with Parameter Variation
5.1. Parameter variation definition
5.1.2. Number of variations and variation codes
NSTVAR IOFPOS ICUVAR IFOVAR MAXIPV RACUPV CHNORM EACUPV

NSTVAR: integer
: Number of steps in parameter variations 
IOFPOS: integer, default: 0
: Code for static offset variation
IOFPOS = 0
: The parameter is not varied 
IOFPOS = 1
: The parameter is varied inNSTVAR
steps according to subsequent specification


ICUVAR: integer, default: 0
: Code for current variation
ICUVAR = 0
: The parameter is not varied 
ICUVAR = 1
: The parameter is varied inNSTVAR
steps according to subsequent specification


IFOVAR: integer, default: 0
: Code for specified force variation
IFOVAR = 0
: The parameter is not varied 
IFOVAR = 1
: The parameter is varied inNSTVAR
steps according to subsequent specification


MAXIPV: integer, default: 1
: Maximum number of iterations for each variation 
RACUPV: real, default:
\(\mathrm {10^{5}}\): Required accuracy measured by displacement norm 
CHNORM: character(4), default: DISP
: Convergence norm switch = DISP
: Use the default Euclidean displacement norm only = BOTH
: Use both the default Euclidean displacement norm and the energy norm 
EACUPV: real, default:
\(\mathrm {10^{5}}\): Required accuracy measured by energy norm  Dummy ifCHNORM=DISP
The total number of load steps in parameter variation is NSTVAR
.
All parameter for which variations are specified, are varied simultaneously
Information about parameter values are to be specified in the subsequent data groups. The initial configuration as specified according to data section B is automatically taken as the first case.
ICURIN
must be greater than zero and CURFAC
must be 1.0 (See
External, static loads).
5.1.3. Load types to be activated. One line for each load type. Optional input, maximum 4 specifications.
LOTYPE ISPEC

LOTYPE: character(4)
: Load type to be applied
= FRIC
: Activate bottom friction forces 
= SPRI
: Activate global and geotechnical springs 
= MEMO
: Activate material memory formulation (Isotropic/kinematic hardening) 
= BOUN
: Boundary change


ISPEC: integer
: Parameter used for further description of applied load type:
LOTYPE = BOUN
:
ISPEC = NBOUND
; Number of nodes with change in boundary conditions.


ISPEC
is dummy for other load types

If specified load type is activated before, the input given here is disregarded.
Activation of sea floor friction is given by FRIC
.
Specification of boundary change, 2 x NBOUND lines
Identification of node for boundary change
IREFID ILSEG ILNODE IOP

IREFID: character(8)
: Reference to line or supernode identifier. 
ILSEG: integer
:
If
IREFID
refers to a line,ILSEG
is the segment number within this line 
If
IREFID
refers to a supernode,ILSEG
must be zero


ILNODE: integer
:
If
IREFID
refers to a line,ILNODE
is the node number within segmentILSEG

If
IREFID
refers to a supernode,ILNODE
must be zero


IOP: integer
: Parameter for boundary change option
= 0
: Boundary conditions: fixed, prescribed or free 
= 1
: Boundary conditions: rigid node connection (The node will become a slave node.)

Ordinary (line end) supernodes and SIMO body nodes with
CHLOCA_OPT=POSI
may have boundary change.
Status for nodal degrees of freedom. To be given if IOP = 0
IPOS IX IY IZ IRX IRY IRZ

IPOS: integer
: Boundary condition type
IPOS = 0
: The node is fixed in global system 
IPOS = N
: The node is attached to support vessel no N


IX: integer
: Boundary condition code for translation in Xdirection
IX = 0
: Free 
IX = 1
: Fixed of prescribed


IY: integer
: Boundary condition code for translation in Ydirection
Same interpretation as for
IX
.


IZ: integer
: Boundary condition code for translation in Zdirection
Same interpretation as for
IX
.


IRX: integer
: Boundary condition code for rotation around Xdirection
Same interpretation as for
IX
.


IRY: integer
: Boundary condition code for rotation around Ydirection
Same interpretation as for
IX
.


IRZ: integer
: Boundary condition code for rotation around Zdirection
Same interpretation as for
IX
.

Identification of master node. To be given if IOP = 1
LINEID ILSEG ILNODE

LINEID: character(8)
: Reference to line ID 
ILSEG: integer
: Segment number within the actual line 
ILNODE: integer
: Local node number within segment
5.1.4. Variation of static positions
This data group is relevant only if IOFPOS=1
.
Static position increments
CHIREF DXOFF DYOFF DZOFF IROT DROT

CHIREF: character(8)
: Reference to moving point
CHIREF = IVES
: Support vessel numberIVES

CHIREF = SNOD_ID
: Supernode identifier.SNOD_ID
must refer to a supernode with specified position


DXOFF: real, default: 0
: Displacement increment, Xdirection \(\mathrm {[L]}\) 
DYOFF: real, default: 0
: Displacement increment, Ydirection \(\mathrm {[L]}\) 
DZOFF: real, default: 0
: Displacement increment, Zdirection \(\mathrm {[L]}\) 
IROT: integer, default: 0
: Rotation code
IROT = 0
: No rotation 
IROT = 1
: The given rotation is taken about Xaxis 
IROT = 2
: The given rotation is taken about Yaxis 
IROT = 3
: The given rotation is taken about Zaxis


DROT: real, default: 0
: Rotation increment \(\mathrm {[deg]}\)
Dummy if
IROT=0

If a support vessel is specified (IREF=IVES
) the displacement
increments refer to the support vessel coordinate system. Otherwise the
increments refer to the global coordinate system.
Only rotation around the Zaxis may be given if IREF = IVES
If the supernode has boundary conditions specified in a skew coordinate
system or in the vessel system, displacements and the rotation increment
DROT
take place in the skew / vessel system. It should also be noted
that the orientation of such a skew coordinate system is kept constant
during the static position incrementation (relevant for AR systems
only).
5.2. Variation of current velocity and direction
This data group is relevant only if ICUVAR=1
.
5.2.2. Current velocity and direction increments
DCUVEL DCUDIR

DCUVEL: real, default: 0
: Current velocity increment \(\mathrm {[L/T]}\) 
DCUDIR: real, default: 0
: Current direction increment \(\mathrm {[deg]}\)
In the case of multilayer current specification, these increments are interpreted as follows.

DCUVEL: This applies directly to the uppermost layer. The lower layers are incremented in the same proportion, so that the shape of the current profile is maintained.

DCUDIR: This applies to all current layers, so that the whole current profile is rotated the same amount.
5.3. Variation of specified forces
This data group is relevant only if IFOVAR=1
and NLCOMP >= 1
(See
Definition of subsequent input).
5.4. Control parameters for printing of results
5.4.2. Control parameters for print of results from static parameter variation analysis
ISTEP ISFOR ISPOS

ISTEP: integer, default: 1
: Step interval for print of specified parameters.
Print is given for the following steps: 1, 1+
ISTEP
, 1+2 \(\mathrm {\times }\)ISTEP
, 1+3 \(\mathrm {\times }\)ISTEP, …, NSTVAR

ISTEP = 1
: Gives print of results for all variation steps


ISFOR: integer, default: 1
: Parameter for print of forces
ISFOR = 0
: No print of external forces 
ISFOR = 1
: Print of external force components in global x, y, z direction at all supernodes with the following status codes:TSNFX, TSNFX2, TSNPOSI1

Not yet implemented


ISPOS: integer, default: 1
: Parameter for print of position
ISPOS = 0
: No print of positions 
ISPOS = 1
: Print of x, y and z coordinates for all free supernodes (i.e. status codeTSNBRA
andTSNFRE
)

6. Static Analysis with Updated Drag Forces
An important consequence of VIV response is increased inline current
forces. One of the key results from the VIVANA
program is therefore
drag amplification factors along the structure. The objective of this
input is to enable static and dynamic analysis using the updated drag
forces.
To use this option the RIFLEX
program modules must be run in the
following order:  INPMOD
 STAMOD
 VIVANA
 STAMOD
with the
drag amplification data group specified
Note that drag amplication cannot be used in combination Specification of marine growth profile.
6.2. Specification of file for input of drag amplification, one input line
CHFDRG CHIOP

CHFDRG: character(60)
: File with drag amplification coefficient; e.g. case22_vivana.mpf 
CHIOP: character(60)
: Format of file with drag amplification coefficients
The CHFDRG
file may be generated by running VIVANA
.
The only file type currently available is the MatrixPlot file format.
Thus; CHIOP = MPF
.
7. Description of Additional Input Files
7.1. Define Stressfree Configuration
The file CHFCON
specified in Data Group B: Static Analysis with Fixed Parameters, contains definition of
stressfree configuration. The file is a free format sequential
ASCIIfile.
The file description depends on the parameter KFORM
specified in
Define stressfree configuration.
File description: KFORM = 1
.
7.1.1. Number of nodes, one input line
NFSNOD

NFSNOD: integer
: Number ofFEM
nodes for which coordinates for stressfree configuration are specified. In this versionNFSNOD
must be equal to the total number ofFEM
nodes
7.1.2. Coordinates for stressfree configuration, NFSNOD input lines
INOD X Y Z

INOD: integer
: Node number 1 ≤INOD
≤NFSNOD

X: real
: xcoordinate describing stressfree configuration 
Y: real
: ycoordinate describing stressfree configuration 
Z: real
: zcoordinate describing stressfree configuration
The coordinate must be consistent with the stressfree element length
7.2. Define Start Configuration
The file CHFSTA
specified in Finite element analysis from start configuration, STAFEM, contains definition
of start configuration. The file is a free format sequential ASCIIfile.
The file description depends on the parameter KFORM
specified in
Finite element analysis from start configuration.
File description: KFORM = 1
.
7.2.1. Number of nodes, one input line
NFSNOD

NFSNOD: integer
: Number ofFEM
nodes for which coordinates for stressfree configuration are specified. In this versionNFSNOD
must be equal to the total number ofFEM
nodes
7.2.2. Coordinates and nodal rotations for start configuration, NFSNOD input lines
The start configuration is defined by the global coordinates of the node and the nodal rotations from the stressfree to the start configuration. In the stressfree configuration the nodal axes are parallel with the global system.
Note that node numbers must be given increasing order
INOD X0 Y0 Z0 T11 T12 T13 T21 T22 T23 T31 T32 T33

INOD: integer
: Node number 1 ≤INOD
≤NFSNODI

XG: real
: Global xcoordinate describing start configuration 
YG: real
: Global ycoordinate describing start configuration 
ZG: real
: Global zcoordinate describing atart configuration
Nodal rotation from the stressfree to the start configuration. Since the stressfree nodal axes are parallel with the global, this is equivalent to specifying the nodal axes in the global coordinate system Dummy for nodes only connected to bar elements.

Nodal xaxis in global system

T11: real
: component in global xdirection 
T12: real
: component in global ydirection 
T13: real
: component in global zdirection


Nodal yaxis in global system

T21: real
: component in global xdirection 
T22: real
: component in global ydirection 
T23: real
: component in global zdirection


Nodal zaxis in global system. Dummy input. The zaxis is found as the cross product of the xaxis and the yaxis.

T31: real
: component in global xdirection 
T32: real
: component in global ydirection 
T33: real
: component in global zdirection

7.3. Define uneven seabed geometry
The seabed geometry data is given on a regularly spaced grid. The grid can be rotated and translated relatively to the reference system of the seabed geometry file. (In addition the reference system of the seabed geometry file can be rotated relatively to the global reference system ref. Coordinates of the seabed file reference system).
A MATLAB script is available, to generate such a file from data given as a set of x, y, z coordinates, see MATLAB script to generate a 3D seafloor grid.
At each step of the static and dynamic analysis, it is checked that every node of the model has x and y coordinates that are within the grid. Excursions from the grid will cause the program to terminate.
7.3.2. Grid dimension and extension, one input file
NGX NGY XSmin XSmax YSmin YSmax DGX DGY

NGX: integer
: Number of points in the grid in the x direction 
NGY: integer
: Number of points in the grid in the y direction 
Xsmin: real
: Coordinate of the first point in the grid in the x direction \(\mathrm {[L]}\) 
Xsmax: real
: Coordinate of the last point in the grid in the x direction \(\mathrm {[L]}\). Used to check consistency of the grid input and whether a node is outside the grid. 
Ysmin: real
: Coordinate of the first point in the grid in the y direction \(\mathrm {[L]}\) 
Ysmax: real
: Coordinate of the last point in the grid in the y direction \(\mathrm {[L]}\). Used to check consistency of the grid input and whether a node is outside the grid. 
DGX: real
: Distance between grid points in the x direction \(\mathrm {[L]}\) 
DGY: real
: Distance between grid points in the y direction \(\mathrm {[L]}\)
The x and y coordinates of the grid corners and the distances between grid ponts are converted to integer values with unit \(\mathrm {[L/100]}\).
7.3.3. Grid orientation, one input line
XOL YOL ANGOL

XOL: real
: xcoordinate of the origin of the grid, in the seabed file reference system \(\mathrm {[L]}\) 
YOL: real
: ycoordinate of the origin of the grid, in the seabed file reference system \(\mathrm {[L]}\) 
ANGOL: real
: Angle between the x axis of the grid and the x axis of the seabed file reference system (positive anticlockwise) \(\mathrm {[deg]}\)
For details see Grid reference system to seabed system.
7.3.4. Seabed gridpoint coordinates, NGY input lines
IZBOT1 ........ IZBOTngx

IZBOT1: integer
: 100 \(\mathrm {\times }\) vertical coordinate of the seabed at the first x value \(\mathrm {[L/100]}\). Given in the seabed file reference system. 
.

.

.

IZBOTngx: integer
: 100 \(\mathrm {\times }\) vertical coordinate of the seabed at the last x value \(\mathrm {[L/100]}\). Given in the seabed file reference system.
The seabed file reference system is defined in Coordinates of the seabed file reference system and shown in Grid reference system and Grid reference system to seabed system.
The input line may be given over several lines of text by using
the continuation character & .
