AUTOMATIC OFFSHORE INSTALLATION AUTOMATIC OFFSHORE INSTALLATION

Both the strength and weakness of MOSES is its flexibility; there is virtually nothing that one cannot accomplish provided they are willing to spend the time. While the flexibility allows one to analyze everything, the price one pays is the cost of learning. If, however, one is willing to establish some rules and to decide on a fixed objective for a given analysis, then that analysis becomes routine.

A system of macros has been developed for the analyses of the installation of a jacket, deck, or other structure. In general, they can be used for loadout, transportation, lift, upend and launch. Considerable flexibility has been incorporated into this system so that most cases can be easily considered. This system has been designed so that several simulations that represent different phases of a structure can be performed, load cases generated, and one code check over all load cases can be produced.

With this system, one defines all of the data necessary for a transportation, launch, upend, lift or loadout analysis of a structure in a single data file with each analysis using the same data. There are two general rules here to which one must adhere:

     The dimension cannot be changed during the analysis
     One must use a barge which conforms to conventions

By a barge conforming to conventions, we simply mean that all of the basic variables have been set. A library of vessels is provided which conform. If one of these is not suitable, you can prepare a model of your own. In preparing this model, you should use the data file SAMPLE.DATA in the vessels library and which is discussed here.

To use this system, you should first read the documentation and then copy files install.dat and install.cif from /ultra/hdesk/tools/install to your working directory or by clicking here, and then modify them to suite your problem. Most of the work is involved with changing install.dat and we will discuss it first.

Most of the data required is defined in this file. The exceptions are the basic model data of the structures to be analyzed and the barge data. The structures data is assumed to be in other files which are inserted. The barge data is also inserted, but it is assumed to be in a special directory which contains all of the barge models.

Basic Data

The data required here is broken down into sections. The first section contains "basic" data required for any analysis and is basically self explanatory. The line

     &DIMEN -SAVE -DIMEN METERS K-NTS

defines the units which will be used in the analysis. Two definitions are available to control the pictures:


     I_SET DO_MOVIE = .TRUE.

and


     I_SET RENDER = -RENDER GL

If the first of these is set .TRUE. then "movies" of a launch and or upending will be created provided you are rendering the pictures with GL. The second one defines the rendering mode of the pictures. If -RENDER GL is set, then pictures will be rendered with GL. To save time, you could use -RENDER WF. Finally, if you are using a "TERMINAL" interface, all pictures will be rendered as WF pictures and no movies will be produced.

The following:


     I_SET WDEPTH = 390

defines the water depth. The "margins", or weight contingencies are defined by the two lines:


     I_SET MARGIN = 5

     I_SET PER_APPLY = 105

The first of these is for the basic steel in the model and the next is for any "joint loads".

The line


     I_SET T_CODE = API WS

defines the type of code checks which will be computed. Here one can specify any code that is accepted by the BEAM_POST or JOINT_POST commands. For transportation, the macros will automatically build the proper load cases, but more information is required:


     I_SET T_CODE = API LRFD  SO_FACTOR SM_FACTOR DM_FACTOR

Here, the static internal forces and restraints are multiplied by SM_FACTOR and combined with DM_FACTOR time the dynamic component before reporting or checking a code. Also, the static case times SO_FACTOR is also checked. One should not use an LRFD code for any other type of analysis.

The line


     I_SET CODE_LIM = 1.33,1e6  1.,1.33  0.9,1.0  0.,0.9

defines the limits for the code check and joint check reports. If you do not change this line, then the checks will be broken down ratios between 1. and 1.33, the next for ratios between .9 and 1, and the last for ratios between 0 and .9.

The elements for which code checks and/or fatigue will be performed are defined by the following:


     I_SET C_CODE = -SELECT @ -EXCEPT ~dum@

     I_SET N_CODE = -SELECT @ -EXCEPT

     I_SET N_FAT = -SELECT @ -EXCEPT

Here, CLASS defines a variable that is used to determine the classes which will be considered for all three categories. If a class is not defined here, no element in this class will be considered for Beam Check, Joint Check, or Joint Fatigue. N_CODE is a variable which defines the joints which will be considered. If a joint is not selected, no results for Joint Check or Joint Crushing will be produced for this joint. Finally, N_FAT defines the joint to be considered for Joint fatigue.

Fatigue Data

If one wants to consider fatigue, then he must define several things. One thing, which is essential, is that the duration data which will be used must be specified. This is with an option of the transportation macro and is discussed below. Also, one may wish to alter one or more of the following:


     I_SET FAT_LIM = 1.,1.e6 0.25,1 0,0.25

     I_SET SCF = Efthymiou

     I_SET SN = XP

     I_SET B_SN = AWSE

The first of these defines the limits for which the fatigue reports will be broken down. If this is not changed, one will receive 3 reports for joint and beam fatigue: The first will have CDRs above 1, the second will have CDRs between .25 and 1, and the last will have CDRs between 0 and .25. The next two lines deal with tubular joint fatigue. Here, SCF defines the type of SCFs which will be computed during fatigue. The SN variable defines the SN curve for Joint Fatigue. In either of the variables, multiple curves can be used. For example,


     I_SET SN = XP X

will produce fatigue results for both the XP and the X curves. The B_SN variable defines the SN curve which will be used for Beam Fatigue, and the &REP_SELECT command defines a new type of SN curve, AWSE. Here, the default SCFs for beam which are not tubes are set to 1, and the AWSE curve is used for beam fatigue.

Report Data

The following command defines the cover page for the report. Be sure to enclose the variables in single quotes(') if they are more than one word.


     I_BEGIN,-OPTIONS

And the available options are:



     -TLINE1, 'XYZ EXPLORATION and PRODUCTION'


     -TLINE2, '8 Pile Jacket for the COWABUNGA Field'


     -TLINE3, 'Installed Offshore Timbuktu'


     -CLIENT, 'QRS Engineering, Inc'


     -FOOTER, '8 Leg Jacket'

Barge Data

This data is necessary only for a launch or transportation.

     USE_VES BARGE

The data for the barge being used is more restrictive than that for the structure. Again, guidance on how to make your own barge model can be found here. The reason for this is that the barge tilt beam data and many other things are necessary. Thus, the barge used must be one of the barges supplied, or a new barge defined in the same format. Here, BARGE, should be the name of the barge one wishes to use.

Structure Data

This section of data needs to be completed for any analysis. Here, one is calling a macro which sets up the data required for each structure to be analyzed. The syntax of the macro is:


     MODEL_IN, NAME, FILE, X, Y, Z, -OPTIONS

And the available options are:


     -PORT_NODES, *P1, *P2, *P3 ...

     -STBD_NODES, *S1, *S2, *S3 ...

     -ORIENT, *O1, *O2, *O3

     -TOP_NODE, *TOP_NODE

     -EXTREMES, P_NAM(1), *P_NODE(1), P_NAM(2), *P_NODE(2) ...

The variable "FILE" defines the file which contains the model for the structure.

Even thou the -PORT_NODES and -STBD_NODES are listed as options they are necessary. If you have a transportation analysis with multiple structures, you should have a "MODEL_IN" for each structure. Sometimes you may have a jacket and deck on the same barge, or two deck sections on the same barge. The MODEL_IN command can also be used to input files that describe miscellaneous cargo, such as piles or boat landings. In this case, FILE for each cargo would contain the appropriate commands to adequately describe the cargo, such as PGEN and #WEIGHT.

The variable "NAME" defines the type of structure. Any name up to eight characters may be used, but the names JACKET and TRIPOD are special. Also, for multiple structures on one barge, the first three characters of the name must be unique. This definition controls the type of connections which are established for transportation and the initial setup for upending. For upending with a type of TRIPOD, the axes system will not be moved when slings are added.

The variables X, Y and Z define the location of the "origin" of the structure on the barge. Here, X is the location aft of the bow, Y the distance off of the centerline and Z is the height above the barge deck. The meaning of origin changes with how the structure is oriented. Normally, the two options -PORT_NODES and -STBD_NODES define the orientation. If they orient the body, the origin is the midpoint of the trailing port and starboard nodes. If the -ORIENT option is used, the origin is the first node specified.

The two options -PORT_NODES and -STBD_NODES are used to define the names of the nodes on the "launch legs". The first node for each variable is the node at the leading edge of the jacket and the last is the node at the trailing edge of the jacket. The leading edge is defined as the end of the jacket that enters the water first. The PORT_NODES are on the port side of the barge while the STBD_NODES are on the starboard side. When specified, these nodes define the orientation of the structure on the barge. They are also used to define barge/structure connections if a V_LWAY connection is specified or if one performs a loadout analysis.

For a structure which is not symmetrical about the barge centerline the orientation scheme is different. Here, the -ORIENT option is used. This option defines three nodes. The first node is where distances for positioning will be measured and is normally at the bottom of the leg that is parallel with the deck edge, assuming the top of jacket faces aft. The second node is along the leg from the first node, and the third node is on the other side of the barge, usually along the horizontal level in line with the first node. Y is the distance from the centerline of the barge to the first node, positive towards starboard. Note that if one specifies starboard nodes and a negative Y then the jacket will be placed under the barge.

-TOP_NODE option is used for an initial guess during upending and stability springs for other types of analysis. This node should be on the face of the structure which is the highest above the water in the initial floating position and should not be attached to any slings.

Points used for reporting purposes can be specified with the -EXTREMES option. Here, a point name and node name is required for each point of interest. For a jacket, these are normally the top and bottom nodes of each corner leg.

For deep water fixed leg structures, the inside diameter of leg compartments can vary substantially. For these situations, there is a useful command for defining very accurate tank definitions, which has the following syntax:


     I_TANK, TANK_NAM, *BOT_NOD, *TOP_NOD, E_BOT, E_TOP, -OPTIONS

And the available options are:


     -F_VALVE, VF_DIA, VF_DIST

     -V_VALVE, VV_DIA, VV_DIST

     -ELEVATION

     -PERMEABILITY, PERM

     -B_NODES, BN(1), BN(2), ....

Here, TANK_NAM is the name given to the tank, and *BOT_NOD and *TOP_NOD are the names of the bottom and top nodes on the jacket leg where the tank resides. The variables E_BOT and E_TOP provide the locations of the bottom and top of the tank, respectively. These are the bulkhead locations inside the leg. If this information is not supplied, the bulkhead locations will be assumed to be at the bottom and top nodes. If the -ELEVATION option is used, these bulkhead locations will be assumed to be jacket elevations, where the jacket origin is at the inplace waterline, and Z is vertical up. Without this option, the bulkhead locations are assumed to be the length along the leg from the bottom node. Bulkhead locations are specified in feet or meters, depending on the current units. The diameter and location of the flood and vent valves are specified with the -F_VALVE and -V_VALVE options. For this information, valve diameter is specified in inches or millimeters, and the valve location is specified in feet or meters. The valve locations here are according to the use of -ELEVATION. If no valve information is provided, a 4 inch flood valve will be located at the bottom node, while a 4 inch vent valve will be placed at the top node. The -PERMEABILITY option allows one to specify the permeability for the tank. Normally legs which contain tanks are straight. The -B_NODES option allows one to specify joints at which the leg has a break in slope. The I_TANK command will use the jacket model to prepare the proper TUBTANK definitions, capturing all the changes to inside diameter along the elements defining a jacket leg, including changes to segments in the elements.

Connector Data

There are three different categories of connectors that can be defined for use in a simulation: SLINGS, TIEDOWN CONNECTORS and VERTICAL SUPPORTS. Each of these categories uses the I_CONNECTOR command, followed by a type description and then the required data.

To define an upending sling assembly for use in a jacket upending analysis, a type of UP_SLING is used, and has the following syntax:


     I_CONNECTOR UP_SLING, *U1, L1, *U2, L2, ...

The data that follows the connector type is a set of node names and harness lengths in feet or meters. The number of pairs defined gives the number of sling elements which will be attached. For a body name of JACKET, the order of the nodes is used to define the local body system. The origin of this system is the midpoint of the vector connecting the first two sling nodes. The local Y axis is in the direction of the first node toward the second, the local Z axis is from the second node to the third and the local X axis is given by the right hand rule.

To perform a lift analysis, you will need a connector type of LIFT_SLING:

     I_CONNECTOR LIFT_SLING, *L1, LEN1, *L2, LEN2, *L3, LEN3, *L4, LEN4

A sling will be constructed from each of the nodes specified to the common hook point.

Tiedown connectors for a transportation analysis can be defined using the following I_CONNECTOR types:


     I_CONNECTOR 4_TIE, ~TD_CLASS,  *TIE1, *TIE2, ...

     I_CONNECTOR V_BRACE, ~TD_CLASS,   *TIE1, *TIE2, ...

     I_CONNECTOR P_BRACE, ~TD_CLASS,   *TIE1, *TIE2, ...

     I_CONNECTOR H_BRACE, ~TD_CLASS,   *TIE1, *TIE2, ...

     I_CONNECTOR PCONNECT, TIEDOWN, DATA

     I_CONNECTOR XY_DELTA, ~TD_CLASS, DELTA_X, DELTA_Y, *TIE1, *TIE2, ...

When the 4_TIE connector type is specified, 4 tiedowns with the properties of ~TD_CLASS will be generated at each node specified. The ~TD_CLASS must be defined before it is referenced on the I_CONNECTOR 4_TIE command. The tiedowns will be arranged in star pattern, with each tiedown 45 degrees from a longitudinal axis that passes through the tiedown node and is parallel to the barge centerline. The longitudinal and transverse distance from the referenced structure node to the deck end of the tiedown is the same as the vertical distance of the referenced node above the barge deck.

Connectors types of V_BRACE, P_BRACE and H_BRACE are all very similar to one another. The names here refer to Vertical Brace, Pitch Brace, and Horizontal Brace, respectively. The V_BRACE takes only dynamic vertical load, no gravity load, and creates an element from the referenced node to the barge deck. The P_BRACE takes only longitudinal dynamic load, and creates a horizontal element that is 5 feet or meters long. The H_BRACE takes only transverse dynamic load, and creates a horizontal element from the referenced node to the side shell. As with the 4_TIE type, the referenced ~TD_CLASS must have been previously defined. For all these tiedown types, the connection at the barge end of the tiedown takes no moments, meaning a pinned connection.

If none of the above tiedown connector types are suitable, one can still define connectors explicitly, and place this definition in this file. For tiedowns, this is done with the ICONNECTOR PCONNECT command. While this format allows for any valid PCONNECT data, the following information is normally provided:


     I_CONNECTOR PCONNECT, DX, DY, DZ, ~TD_CLASS, *NOD, *B@

For structure descriptions that include tiedowns, the tiedowns should be removed from the structure file and placed in this file using the above I_CONNECTOR PCONNECT method.

The I_CONNECTOR XY_DELTA command provides an easy way to define tiedowns where the barge end remains at the same height as the referenced node on the structure. DELTA_X and DELTA_Y refer to the distance from the referenced node to the barge end of the tiedown.

Vertical supports that take gravity load can be defined with these I_CONNECTOR types:


     I_CONNECTOR V_LWAY

     I_CONNECTOR V_CAN, ~CAN_CLASS,   *C1, *C2, ... -OPTION

     I_CONNECTOR V_REST, ~REST_CLASS,  *R1, *R2, ...

The V_LWAY type will create a vertical connector using the node names provided on the -PORT_NODES and -STBD_NODES options of MODEL_IN. This will actually create a structural element that simulates the launchway on a barge, using the launchway information provided in the barge model. If this launchway information is not available, a WBOX beam is generated that is 48 inches deep, 48 inches wide, with 1 inch plates for the flanges and sides, and 2 inch plate for the center plate. The connections created here are gap elements. For spectral load cases, only a linear structural solution can be performed, so the gap elements have no effect on these cases. For time domain load cases, a nonlinear structural solution is performed, which involves iteration over the support nodes to release those supports that show tension.

The connector type V_CAN provides a vertical support can with the properties provided by the can class ~CAN_CLASS. A beam element is created from the referenced node to the barge deck, with moments about the local Y and Z axes released at barge end. If one specifies the option -DO_HORIZONTAL, then restraints will be added to prevent lateral motion of the cargo on the barge during stages when the tiedowns are not connected.

A connector type of V_REST works in a similar fashion. Here, simply specify the restraint class and support nodes, and restraints will be provided at each node.

Parametric Studies

For those analyses that will be examining the effects of a change in CG location, or an added weight there is the I_PCASE command. This command will make the requested change and include it as a seperate process.

Parametric studies can be done using the I_PCASE command.


     I_PCASE, BRANCH, PART, DATA

Branch can be: launch, transportation, loadout, upend or lift. The part is the part name as listed in the MODEL_IN command. This is followed by the data. There are 5 pices of data that are possible.

     weight, xcg, ycg, zcg, and friction

The data has to be put in this order. The data can be input as a negative value. The values can be entered as 0 for when that data is not to be changed. The change in CG is in the part system. Several I_PCASE commands can occur in one install.dat file.

Command File

After fixing up install.dat, one should turn to install.cif. Here one has the option to perform different installation simulations, perform the structural analyses, and do one comprehensive structural code check for all load cases. Below, we will discuss the commands to make this happen. The first of these is for a structural loadout analysis:


     INST_LOADOUT, -OPTIONS

And the available options are:


     -VERT_RST

     -GAPDIS, GAPDIS

     -LENSKD, LENSKD

     -FXLOC, FXLOC

     -TOPLOAD

     -PSUPNOD, PNODE(1), PNODE(2), ....PNODE(n)

     -SSUPNOD, SNODE(1), SNODE(2), ....SNODE(n)


     -NO_STRUCT

It is easier to discuss these commands assuming a jacket is the structure being loaded onto a barge, but this can just as easily be used for a deck loadout. This command will move the structure from the land onto the barge and create a load case for structural analysis whenever a structure hard point leaves the land support. Gap elements are used for the supports and a nonlinear structural solution is performed, unless -VERT_RST is used. In this case, rigid restraints would be used instead of gap elements.

The -GAPDIS, -LENSKD, and -FXLOC options define the geometry of the loadout. Here, GAPDIS is the distance between the land skidway and the beginning of the barge skidway and LENSKD is the length of skidway on the barge that actually provides support. FXLOC is the final location of the jacket on the barge. This is a distance from the end of the barge skidway (nominally the bow) to the trailing edge of the jacket. It is positive if the trailing edge of the jacket is aft from the bow, negative otherwise. The trailing edge is defined as the end of the jacket that would come off last if the jacket were being launched from the barge.

It is assumed that the jacket is loaded out with the base of the jacket moving onto the barge first, unless the option -TOPLOAD is exercised. It is further assumed that the stern of the barge is towards the fabrication bulkhead. An over the bow loadout can be analyzed by specifying the proper values for GAPDIS and FXLOC.

The options -PSUPNOD and -SSUPNOD can be used to specify support nodes, if the supports are different from PORT_NODES and STBD_NODES. The variables PORT_NODES and STBD_NODES are defined in install.dat.

This macro is designed to perform a simulation and a corresponding structural analysis by default.

Next, we will discuss the transportation analysis, which has the following syntax:


     INST_TRANSP, -OPTIONS

And the available options are:


     -NO_SEAKEEPING

     -NO_VORTEX

     -NO_STAB

     -NO_STRUCT

     -DRAFT, T_DRAFT

     -TRIM, T_TRIM

     -BALLAST, BAL_SEL

     -AMOUNT, BAL_AMT

     -CMP_BAL, CMP_SEL

     -EQUI

     -DAMAGE, DAM_CMP

     -S_COND, S_C

     -PERIOD, PERIOD(1), ....

     -HEADING, HEADING(1), ...

     -WIND, W_INTACT, W_DAMAGED W_VORTEX, W_STRUCTURAL

     -MO_POINTS, P_NAMES

     -SPEED, SPEED

     -TYPE_SPECT, SPECT_TYPE

     -STEEP, STEEPNESS

     -DO_FREQ

     -DO_TIME, TOB   TINC

     -FLEXIBLE

     -DURATION, DUR_FILE DUR_TIME DUR_VELOCITY

     -TIETEN

     -SACS_TOW, RAO   SNAPSHOT

If one does not want some of the default results, they can turn them off with the -NO_SEAKEEPING, -NO_VORTEX, -NO_STAB, or -NO_STRUCTURAL options. The two options -DRAFT and -TRIM define the draft at the bow and the trim for the tow. If these two options are not used, then a trim of .57 degrees will be used and the draft will be set so that the draft amidships is half the depth. A weight is then computed so that the specified condition is achieved. If, however, the -BALLAST option is used, the situation is different. Here, the variable BAL_SEL is a string containing a set of pairs of tank names and percentages full. If this is specified, then this ballast condition will be used and equilibrium found as the transportation condition. In a similar fashion, the -AMOUNT option allows one to specify a ballast amount, in the current big force units. This must also be in the form of tank name and amount pairs. If the -CMP_BAL option is invoked, MOSES will compute the ballast amount required in each tank listed in CMP_SEL to achieve the specified draft and trim. If the -EQUI option is used, MOSES will consider all the information in the barge and cargo input files, and find an equilibrium condition. The -DAMAGE option defines DAM_CMP which is a list of compartment names which are damaged. If this is omitted, only intact stability will be computed.

The option -S_COND defines the sea states to be considered. Here, specify several sea triples. These three tokens are first a character sea-state identifier, next a wave height and finally a period.

The options -PERIOD and -HEADING define the periods and headings at which the response operators will be computed. If they are omitted, then headings of 0, 45, 90, 135, 180, 225, 270 and 315 and periods of 4, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 13, 15 and 20 seconds are used.

The option -WIND defines the wind speeds used in the analyzes. Here, W_INTACT is the wind speed for intact stability, W_DAMAGED for damaged stability, W_VORTEX for vortex shedding, and W_STRUCTURAL for structural analysis. The defaults are 100, 50, 100, and 100 knots respectively. If W_STRUCTURAL is zero then wind load is not included in structural load cases.

The option -MO_POINTS will provide statistics of g-forces at a point for the point names specified with P_NAMES. This is an easy way to determine the motion accelerations at specified locations on the cargo.

Control of the spectral motions computation is provided with the -SPEED, -TYPE_SPECT and -STEEP options. Here, SPEED is the forward speed of the vessel in knots, and the default is 0 forward speed. SPECT_TYPE can be either ISSC, JONSWAP or a previously defined user spectrum, where ISSC is the default. The -STEEP option specifies the reciprocal of wave steepness, and uses a value of 20 as the default. A value of SPECTRAL can also be used, in which case the first environment specified on -S_COND will be used to linearize the equations of motion.

The default for producing structural load cases for transportation is to create frequency domain spectral load cases, and no particular option is required to make this happen. However, one can also prepare time domain load cases by using the -DO_TIME option. Here, TOB is the total time of observation in seconds, while TINC is the time step increment. What happens next is quite involved for such a deceptively simply option. A time domain synthesis will be performed for the motions of the center of gravity for each piece of cargo, for each environment specified on -S_COND. Then, for each of these environments, the time for the extreme force or moment for each of the six degrees of freedom will be determined. By extreme here, we mean a maximum or minimum, such as positive and negative roll. These times are then used in the creation of deterministic structural load cases. Regardless of the time of observation specified with TOB, the results will be adjusted to reflect a 3 hour simulation. Note that the time domain results used here come from a time domain synthesis, where the waterplane is assumed to remain constant. If only the -DO_TIME option is used, only time domain cases will be created. To provide the frequency domain and time cases in the same run, use both the -DO_FREQ and the -DO_TIME options.

It is prudent to make a quick preliminary run to check the position of the structures on the barge before investing in the longer duration run that performs the entire analysis. For these types of runs, use of the various -NO_ options will turn off the specified computation.

If the -FLEXIBLE option is exercised, the flexibility of the barge will be considered. Otherwise, the barge will be considered as rigid. If tiedowns are included in the model, a sequential structural analysis will be performed. The first pass through the structural solver will create a dead load case without tiedowns, while the second pass will create dynamic load cases including tiedowns. The default action regarding tiedowns is to assume that a tension connection does not exist at the barge end of the tiedown. Another way to say this is the footprint of the tiedown brace lands on a doubler plate, and the welding of the barge deck plate to the web frames underneath is not sufficient to develop tension. For these situations, the load cases for the tiedowns are conservatively multiplied by two. The assumption here is that tiedowns are arranged as inboard/outboard pairs, and the tension that would have otherwise developed on one side goes into compression on the opposite side. If the tiedowns can really develop tension at the barge deck, use the -TIETEN option. In this case, the multiplier for the tiedown load cases will be one.

The -DURATION option is used to define the duration data for fatigue during this process. DUR_FILE is a file containing the duration data for the tow. Also, DUR_TIME is the total time for which the data in DUR_FILE will act and DUR_VELOCITY is the average velocity of the tow.

The -SACS_TOW option is used to emit RAO or acceleration load cases in a format that can be read into SACS as a SACS Tow file. The RAO option will output RAOs for all requested periods and frequencies. The SNAPSHOT option will output accelerations for a SACS Tow file. The SNAPSHOT creates a time synthesis and reports the extremes for each degree of freedom. The extremes are the minimum and the maximum event. The routine filters out any events that occur twice. These accelerations and RAOs are defined at the cg of the jacket model.

One can issue several INST_TRANSP commands. For each command issued a process will be created and the results will be post-processed. This is an automated way in which to consider situations with different drafts, trims, etc and still have a single fatigue results for all of them.

The automated lift analysis needs almost no user involvement, and is invoked with the following command:


     INST_LIFT, -OPTIONS

And the available option is :


     -NO_STRUCT

This command will use the information provided in install.dat to setup the analysis, and prepare lift load cases with appropriate load factors according to API-RP2A. If you only want to determine the equilibrium position using the specified sling lengths and not perform the structural analysis, use the -NO_STRUCT option.

The syntax for the automated launch analysis is shown below:


     INST_LAUNCH, -OPTIONS

And the available options are:


     -DRAFT, L_DRAFT1, L_DRAFT2 ...

     -TRIM, L_TRIM1, L_TRIM2  ...

     -BALLAST, BAL_SEL

     -AMOUNT, BAL_AMT

     -CMP_BAL, CMP_SEL

     -EQUI

     -FRICTION, FRICT

     -MAXANGLE, MAX_ANGLE

     -MAXTIME, MAX_TIME

     -STOP_SEP

     -MAXOSC, MAXOSC

     -WINCH, WINCH

     -NO_REPORT

     -NO_STRUCT

     -FLEXIBLE

     -NONLINEAR

     -ALL_POINT

     -FLX_RIG

     -AMOD, L_AMOD

     -saclcase

This command assumes that an equal number of drafts have been specified with the -DRAFT option and trims have been specified with the -TRIM option. It will perform a launch for each draft and trim pair. If no draft and trim are specified, a single launch will be performed with a trim of 3 degrees and a draft so that the tilt pin is at the water surface. The draft specified on this command is measured at midships.

The data expected after the -BALLAST, -AMOUNT, -CMP_BAL and -EQUI options are the same as for the INST_TRANSP command defined above.

The skidway friction is specified via the -FRICTION option. Likewise, the maximum angle of tilt for the primary tilt beam is specified with the -MAXANGLE option. Normally a launch will proceed until the maximum time (specified with -MAXTIME) is reached or until 5 oscillations of the jacket have been made. However, if the -STOP_SEP option is used, the simulation will stop when the jacket separates from the barge. The -MAXOSC option is used to specify the number of jacket oscillations allowed after separation before the simulation stops. The initial winch speed of the jacket is specified with -WINCH, and the default is 1 foot/second.

If one uses the option, -NO_REPORT, then detailed post-processing will not be performed. This macro is designed to perform a simulation and a corresponding structural analysis by default. If the structural analysis is not required, simply use the -NO_STRUCT option. If SACS compatible loadcases are desired, use the -SACLCASE option. Note that this option has no effect if a nonlinear type of analysis is specified. Also note that this option should only be used in conjunction with the &EMIT -SACS command. See the documentation of that command for further details. When the above conditions are met, the -SACLCASE option will write out the launch loadcases at times of interest. See the LCASE documentation for more details about these launch loadcases. These SACS load cards will be written to the root.ppo file. Load cases correspond to times of interest as found dynamically during the launch process. Note that the loadcases are not processed further. SACS users must supply fixities to use these launch cases appropriately.

The options -FLEXIBLE, -NONLINEAR, -ALL_POINT, -FLX_RIG and -AMOD are used to control various aspects of the structural analysis of a jacket launch. The -AMOD option specifies the allowable stress modifier for the structural code check, and has a default of 1. The other options control the way the solution is constructed:

Of course, with any option that provides gap elements, a non-linear structural solution is produced. If none of the above options are used, a rigid barge is assumed, and the reactions between the jacket and barge are applied to the jacket as distributed loads.

To perform an Automated Upend analysis, one uses the INST_UP command. Which assumes a typical upending sequence, which includes lifting the jacket to provide the specified minimum bottom clearance, flooding the bottom side legs, and then flooding the top side legs. The flooding is performed with a constant hook height. Two upending simulations are actually performed to determine the proper lifting height needed to obtain the minimum clearance. The syntax of the command is:


     INST_UP, -OPTIONS

And the available options are:



     -LIFT_INCREMENT, L_INCREMENT


     -FILL_INCREMENT, F_INCREMENT


     -VENTS_CLOSED, C_LEGS


     -MIN_BOTTOM_CLEAR, MIN_BOT


     -TOP_OF_LEG, TOP_OF_LEG

     -FIRST_FLOOD, FF_TANKS, FF_DESC

     -SECOND_FLOOD, SF_TANKS, SF_DESC

     -DAMAGED_LEG, DAMAGED_LEG

     -NO_STRUCT

The options of this command are used to convey the information needed to perform the upend analysis, and the variable names used here are fairly obvious. The variable L_INCREMENT is the lift increment for the lifting stage of the upend, in the present big length units. F_INCREMENT is the flood increment for the flooding stages, in percent. C_LEGS refers to the names of tanks that have their vent valves closed during flooding, and can be a list of tank names, a selection criterion, or a wild character. MIN_BOT specifies the minimum bottom clearance, and TOP_OF_LEG specifies the distance from the waterline to the top of leg in the final installed position. If this option is used, the jacket will be lowered to this location. In this position, the reported hookload would also be the on bottom weight. The -FIRST_FLOOD option provides input for the names of the tanks to be flooded first, along with a description of these tanks. Tank names used here would normally use the wild character, as shown:

     -FIRST_FLOOD B@ Row B Legs

In this example, all tanks beginning with "B" would be flooded, and tank names would normally be defined as B1Leg and B2Leg, for instance. In a similar fashion, the second stage flooding is described using the -SECOND_FLOOD option. The -DAMAGED_LEG option is used to define the tank assumed to be damaged. With this option, MOSES will return to the original undamaged floating position, and compute a new floating position assuming the specified tank to be open to sea.

This macro is designed to perform a simulation and a corresponding structural analysis by default. If the structural analysis is not required, simply use the -NO_STRUCT option.

The final command in this sequence of simulations and structural solutions provides structural post-processing for all the load cases previously created, and has the following syntax:


     INST_SPOST, -OPTIONS

And the available options are:


     -RESIZE

     -UP_CLASS

     -MEMLOD

     -DEFL

The -RESIZE option instructs MOSES to automatically resize any over stressed members in the model. If the -UP_CLASS option is used, these changes are saved to the database. The -MEMLOD and -DEFL options will provide detailed member loads and joint deflections, respectively.