Automatic Installation Command File

The user 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:

     -GAPDIS, GAPDIS

     -LENSKD, LENSKD

     -FXLOC, FXLOC

     -PSUPNOD, PNODE1, PNODE2, ....PNODEn

     -SSUPNOD, SNODE1, SNODE2, ....SNODEn

     -TOPLOAD

     -VERT_RST

     -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 first three 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 fabricator 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_NOD and STBD_NOD. The variables PORT_NOD and STBD_NOD are defined in install.dat.

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.

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

     INST_TRANSP, -OPTIONS

And the available options are:

     -DRAFT, T_DRAFT

     -TRIM, T_TRIM

     -S_COND, S_C

     -BALLAST, BALSEL

     -AMOUNT, BAL_AMT

     -CMP_BAL, CMPBAL_S

     -EQUI

     -DAMAGE, DAMCMP

     -PERIOD, PERDS

     -HEADING, HDNGS

     -WIND, WI WD WV WS

     -MO_POINTS, P_NAMES

     -SPEED, SPEED

     -TYPE_SPEC, SPECT_TYPE

     -STEEP, STPNES

     -DO_FREQ

     -DO_TIME, TOB   TINC

     -NO_SEAKEEPING

     -NO_VORTEX

     -NO_STAB

     -NO_STRUCT

     -FLEXIBLE

     -TIETEN

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 BALSEL 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 CMPBAL_S 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 variable DAMCMP defines 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, WI is the wind speed for intact stability, WD for damaged stability, WV vortex shedding, and WS for structural analysis. The defaults are 100, 50, 100, and 100 knots respectively. If WS is zero then wind load is not included in structural load cases.

The option -MO_POINTS will provide statistics of motions 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 automated lift analysis needs almost no user involvement, and is invoked with the following command:

     INST_LIFT -NO_STRUCT

And the available options are:

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, BALSEL

     -AMOUNT, BAL_AMT

     -CMP_BAL, CMPBAL_S

     -EQUI

     -FRICTION, FRICT

     -MAXANGLE, MAXANGL

     -MAXTIME, MAXTIM

     -MAXOSC, MAXOSC

     -STOP_SEP

     -WINCH, WINCH

     -NO_REPORT

     -NO_STRUCT

     -FLEXIBLE

     -NONLINEAR

     -ALL_POINT

     -FLX_RIG

     -AMOD, L_AMOD

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 -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.

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:

• -FLEXIBLE Flexibility of the barge is included, pre-tipping and post-tipping load cases use gap elements.
• -NONLINEAR Rigid barge assumption, pre-tipping and post-tipping load cases use gap elements.
• -ALL_POINT Provides gap elements for post-tipping load cases. Without this option, post-tipping cases use the rocker load as applied loads based on a trapezoidal load distribution.
• -FLX_RIG Makes two passes through the structural solver. Before tipping, barge flexibility is included, after tipping, a rigid barge is assumed.

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, the following command is used:

     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 INST_UP command 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 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 overstressed 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.