Input to STAMOD 1. General Information The input to the STAMOD MODULE is divided into 3 main sections, referred to as Data Group A: Control Information Data Group B: Static Analysis with Fixed Parameters Data Group C: Static Analysis with Parameter Variation 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, in-plane 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 group Specification 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 by INPMOD 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 from FEM 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: As IPRFEM=1, but in addition roller contact forces are stored on files, see Riser type specification in INPMOD. Only available in standalone version of RIFLEX. 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 of FEM 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 to OUTMO 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 static FEM 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 FE-analysis and configurations after each load-group during the loading sequence are stored. The stored configurations may be used as start configuration for subsequent STAFEM-analysis. IFILCO=0: No additional files IFILCO=1: Configurations stored to ASCii files: <prefix>_config-lg<i> where the number <i> indicates the load group number. For configurations after parameter variation the files are named: <prefix>_config-lg<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. 3.2.1. Data group identifier, one input line SPECify ARCLength COORdinates 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 by OUTMOD 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 3.4. Data set identifier for present analysis 3.4.1. Data group identifier, one input line RUN IDENtification 3.4.2. Data set identifier for results, one input line IDRES IDRES: character(6): Data set identifier for this run 3.5. Identifier of environment data 3.5.1. Data group identifier, one input line ENVIronment REFErence IDENtifier 3.5.2. Identifier of environment data, one input line IDENV IDENV: character(6): Identifier of environment data given as input to the INPMOD module This data group is dummy for coupled analysis. 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 = EFF-AX-FORCE: Effective tension = RES-CURV: Resultant curvature = LONG-STRESS: Longitudinal stress = ALL: All of the above described responses CHILIN: character: = LINE-ID: 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 Ascii-file. 3.8.1. Data group identifier, one input line STAMod FEM PRINt 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 Ascii-file 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 Non-dimensional drag coefficients Current velocity in global x, y and x-directions 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 Ascii-file. 3.9.1. Data group identifier, one input line STAMod MASS CALC 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) BODY-ID BODY-ID: 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: X-coordinate of output reference frame, in global system, \(\mathrm {[L]}\) YPOS: real: Y-coordinate of output reference frame, in global system, \(\mathrm {[L]}\) ZPOS: real: Z-coordinate of output reference frame, in global system, \(\mathrm {[L]}\) ZROT: real: rotation of the output reference frame about the global Z-axis, \(\mathrm {[deg]}\) 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 3.9.6. Lines to include in summary, NLINES input lines LINE-ID LINE-ID: character(8): name of line to include in summary, one line name per input line 3.9.7. Bodies to include in summary, NBODIES input lines BODY-ID BODY-ID: character(8): name of body to include in summary, one body name per input line 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 ' line-id 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 4.1.1. Data group identifier STATic CONDition INPUt 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 by CURFAC 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. LINE-ID ILSEG ILNODE ILDOF RLMAG CHICOO LINE-ID: 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 to DYNMOD. 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 requires ISOLVR = 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 4.2.1. Data group identifier, one input line COMPutational PROCedure 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: Figure 1. Available options for static and dynamic analysis 4.3. Catenary analysis procedure, CAT 4.3.1. Data group identifier CATEnary ANALysis PARAmeters 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 4.4.1. Data group identifier CATFem ANALysis PARAmeters 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. 4.5.1. Data group identifier STAFem ANALysis PARAmeters 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: Co-ordinates and base vector system given for all FEM-nodes in increasing node number order. Next data group is Incremental loading procedure. 4.6. Finite element analysis, FEM 4.6.1. Data group identifier FEM ANALysis PARAmeters 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 user-defined 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 user-defined 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 in-plane 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 co-ordinates) 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 off-loaded 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. Data group identifier, one input line LOAD GROUP DATA 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 pipe-in-pipe contact forces = ISTR: Initially pre-stressed 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 cross-section changes from growth profile = WIND: Wind forces ISPEC: integer: Parameter used for further description of applied load type: LOTYPE = PIPE: ISPEC = 0 (default): Possible pipe-in-pipe contact enabled (ENTERED) = 1: Specify start condition for pipe-in-pipe 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 user-defined stress-free segment lengths, i. e. gradually during a static load group. If ISTR Initially pre-stressed segments is specified, the fibre rope elongation will be applied in this load group together with any stress-free segment lengths specified by the user. Otherwise, the elongation will be automatically applied in the first load group. Pipe-in-pipe 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: pipe-in-pipe modelled as ENTERED and Example: pipe-in-pipe modelled as NOT ENTERED below. Figure 2. Example: pipe-in-pipe modelled as ENTERED Figure 3. Example: pipe-in-pipe modelled as NOT ENTERED Temperature variation, NLSPEC input lines only given if LOTYPE = TEMP LINE-ID ISEG IEC TEMP LINE-ID: 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 cross-sectional 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 MRL-ID PRESSI DPRESS VVELI MRL-ID: 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 . IREF-ID ILSEG ILNODE IOP IREF-ID: character(8): Reference to line or supernode identifier. ILSEG: integer: If IREF-ID refers to a line, ILSEG is the segment number within this line If IREF-ID refers to a supernode, ILSEG must be zero ILNODE: integer: If IREF-ID refers to a line, ILNODE is the node number within segment ILSEG If IREF-ID refers to a supernode, ILNODE must be zero IOP: integer: Parameter for boundary change option = 0: Boundary conditions: fixed, pre-scribed 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 X-direction IX = 0: Free IX = 1: Fixed of prescribed IY: integer: Boundary condition code for translation in Y-direction Same interpretation as for IX. IZ: integer: Boundary condition code for translation in Z-direction Same interpretation as for IX. IRX: integer: Boundary condition code for rotation around X-direction Same interpretation as for IX. IRY: integer: Boundary condition code for rotation around Y-direction Same interpretation as for IX. IRZ: integer: Boundary condition code for rotation around Z-direction Same interpretation as for IX. Identification of master node. To be given if IOP = -1 LINE-ID ILSEG ILNODE LINE-ID: 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 pre-bent 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. 4.8.1. Data group identifier DEFIne STREssfree 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 co-ordinates given for all FEM-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. 4.9.1. Data group identifier BOTTom GEOMetry FILE 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: x-coordinate 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: y-coordinate 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: z-coordinate of the origin of the seabed file reference system, in the global reference system, see Seabed reference system to global coordinates in z-direction. \(\mathrm {[L]}\) ANGOS: real, default: 0: Angle between the x-axis of the seabed file reference system and the x-axis of the global reference system (positive anti-clockwise), see Seabed reference system to global coordinates. \(\mathrm {[deg]}\) Figure 4. Seabed reference system to global coordinates Figure 5. Seabed reference system to global coordinates in z-direction 5. Data Group C: Static Analysis with Parameter Variation 5.1. Parameter variation definition 5.1.1. Data group identifier, one input line 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 in NSTVAR 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 in NSTVAR 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 in NSTVAR 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 if CHNORM=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). See also Note: Static Analysis with Fixed Parameters and Parameter Variation. 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 IREF-ID ILSEG ILNODE IOP IREF-ID: character(8): Reference to line or supernode identifier. ILSEG: integer: If IREF-ID refers to a line, ILSEG is the segment number within this line If IREF-ID refers to a supernode, ILSEG must be zero ILNODE: integer: If IREF-ID refers to a line, ILNODE is the node number within segment ILSEG If IREF-ID refers to a supernode, ILNODE must be zero IOP: integer: Parameter for boundary change option = 0: Boundary conditions: fixed, pre-scribed 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 X-direction IX = 0: Free IX = 1: Fixed of prescribed IY: integer: Boundary condition code for translation in Y-direction Same interpretation as for IX. IZ: integer: Boundary condition code for translation in Z-direction Same interpretation as for IX. IRX: integer: Boundary condition code for rotation around X-direction Same interpretation as for IX. IRY: integer: Boundary condition code for rotation around Y-direction Same interpretation as for IX. IRZ: integer: Boundary condition code for rotation around Z-direction Same interpretation as for IX. Identification of master node. To be given if IOP = -1 LINE-ID ILSEG ILNODE LINE-ID: 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. Data group identifier STATic OFFSet INCRements Static position increments CHIREF DXOFF DYOFF DZOFF IROT DROT CHIREF: character(8): Reference to moving point CHIREF = -IVES: Support vessel number IVES CHIREF = SNOD_ID: Supernode identifier. SNOD_ID must refer to a supernode with specified position DXOFF: real, default: 0: Displacement increment, X-direction \(\mathrm {[L]}\) DYOFF: real, default: 0: Displacement increment, Y-direction \(\mathrm {[L]}\) DZOFF: real, default: 0: Displacement increment, Z-direction \(\mathrm {[L]}\) IROT: integer, default: 0: Rotation code IROT = 0: No rotation IROT = 1: The given rotation is taken about X-axis IROT = 2: The given rotation is taken about Y-axis IROT = 3: The given rotation is taken about Z-axis 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 Z-axis may be given if IREF = -IVES If the supernode has boundary conditions specified in a skew co-ordinate 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 co-ordinate 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. 5.2.1. Data group identifier, one input line CURRent VARIation INCRements 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). 5.3.1. Data group identifier, one input line SPECified FORCe INCRements 5.3.2. Force increments, NLCOMP input lines to be given DRLMAG DRLMAG: real, default: 0: Force increment on specified forces RLMAG (F or FL). See Additional, static load components. 5.4. Control parameters for printing of results 5.4.1. Data group identifier, one input line STAMod PRINt CONTrol 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 code TSNBRA and TSNFRE) 6. Static Analysis with Updated Drag Forces An important consequence of VIV response is increased in-line 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. 6.1. Data group identifier, one input line DRAG AMPLIFICATION INPUT 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 ASCII-file. 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 of FEM-nodes for which coordinates for stressfree configuration are specified. In this version NFSNOD must be equal to the total number of FEM-nodes 7.1.2. Coordinates for stressfree configuration, NFSNOD input lines INOD X Y Z INOD: integer: Node number 1 ≤ INOD ≤ NFSNOD X: real: x-coordinate describing stressfree configuration Y: real: y-coordinate describing stressfree configuration Z: real: z-coordinate 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 ASCII-file. 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 of FEM-nodes for which coordinates for stressfree configuration are specified. In this version NFSNOD must be equal to the total number of FEM-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 stress-free to the start configuration. In the stress-free 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 x-coordinate describing start configuration YG: real: Global y-coordinate describing start configuration ZG: real: Global z-coordinate describing atart configuration Nodal rotation from the stress-free to the start configuration. Since the stress-free 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 x-axis in global system T11: real: component in global x-direction T12: real: component in global y-direction T13: real: component in global z-direction Nodal y-axis in global system T21: real: component in global x-direction T22: real: component in global y-direction T23: real: component in global z-direction Nodal z-axis in global system. Dummy input. The z-axis is found as the cross product of the x-axis and the y-axis. T31: real: component in global x-direction T32: real: component in global y-direction T33: real: component in global z-direction 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. 7.3.1. Description text of geometry CHBOTT CHBOTT: character: Descriptive text of geometry 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: x-coordinate of the origin of the grid, in the seabed file reference system \(\mathrm {[L]}\) YOL: real: y-coordinate 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 anti-clockwise) \(\mathrm {[deg]}\) 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 &. Figure 6. Grid reference system Figure 7. Grid reference system to seabed system References Input to DYNMOD