Altering Connectors Altering Connectors

So that many different situations can be analyzed, MOSES provides the ability to partially alter the definition of the connector system. This is performed with one command, &CONNECTOR, which has several options, most being applicable to a particular class of connector. The form of this command is:


     &CONNECTOR, :CONN_SEL(1,1),  ..., :CONN_SEL(n,1), -OPTION(1), \
     :CONN_SEL(1,2),  ..., :CONN_SEL(n,2), -OPTION(2), \
     :CONN_SEL(1,m),  ..., :CONN_SEL(n,m), -OPTION(m)

where the options applicable to all connectors are:



     -INACTIVE


     -ACTIVE

which makes a set of connectors inactive or active. Each option operates on the list of connectors immediately preceding it. The first option defines the connectors whose names are selected by the selectors :CONN_SEL(i) to be inactive. Inactive connectors can be reactivated by simply issuing the second option.

For connectors with types of ROD, SL_ELEM, B_CAT, and H_CAT more things can be accomplished with &CONNECTOR. To alter the length of the first segment of a line, use the options:


     -LENGTH, LEN

     -L_DELTA, DLEN

     -L_HORIZONTAL, FORCE

     -L_TENSION, FORCE

Here, :CONN_SEL(i,j) are the selectors for lines whose length will be altered, and the method of specifying the new length is controlled by the options. If one uses -LENGTH, he is simply defining each line which matches the selectors to have a length of the first segment of LEN (feet or meters). Using -L_DELTA is similar to the above except that DLEN (feet or meters) is added to the existing length. Alternately, one could specify either -L_HORIZONTAL or -L_TENSION. With these options, a new length of the first segment will again be defined, but here, the new length is calculated so that either the tension or horizontal force has the value FORCE in the initial configuration.

To alter the location of the anchor, use the options:


     -ANCHOR, XA, YA, ZA

     -A_HORIZONTAL, FORCE

     -A_TENSION, FORCE

Here, :CONN_SEL(i,j) are the selectors for lines whose anchor location will be altered, and the method of specifying the new location of the anchor is controlled by the options. If one uses -ANCHOR, he is simply defining the global x, y and z coordinates (feet or meters) of the anchor of each line which matches the selectors. The z coordinate specified here is honored for all flexible connectors except a type of H_CAT, where it is ignored. Alternately, one could specify either -A_TENSION or -A_HORIZONTAL which instructs MOSES to compute the location so that either the tension or horizontal force has the value FORCE in the initial configuration.

The force of H_CAT connectors is computed with the aid of a "lookup table". The force properties of the line are computed as a function of distance from the anchor and stored in a table when the connector is defined or its properties changed. Now, this table produced quite accurate results for changes in horizontal directions, but the changes due to vertical motion are approximated. If one is interested in moving a body vertically, he may need to recompute the table as the body moves. The The option



     -G_TABLE}

will force MOSES to recompute the table at the current position.

For ROD connectors, three additional things can be altered with the &CONNECTOR command with the options:


     -A_STIFF, STADGX, STADGY, STADGZ

     -TOP_MOMENT, YES/NO

     -ST_ADDITION, INONUM, STADGX, STADGY, STADGZ

     -ZERO_BSTIF, YES/NO

Normally, the top of the rod is "pin" connected to the body, and a default stiffness is assigned for the connection at the first node (the "anchor"). The default depends on the type of rod: if it is a "straight rod" a large stiffness is used, while for a "mooring line" type of rod a much smaller stiffness is defined. The option -A_STIFF allows one to redefine the anchor stiffness. Here, STADGX, STADGY, and STADGZ are the global X, Y, and Z values of the stiffness in bforce/blength. If one uses -A_STIFF 0 0 0, then the rod will have no restraint at the anchor. Similarly, the -TOP_MOMENT option changes the connection behavior at the top. If it is used with a YES/NO of YES, then the top connection will apply a moment; otherwise, it will apply only forces. The -ZERO_BSTIF option changes the connection behavior at the bottom. If it is used with a YES/NO of YES, then the stiffness at the bottom will be applied, otherwise the bottom will be free to move.

The option -ST_ADDITION allows one to add a diagonal stiffness matrix at intermediate points along the rod. Here, INONUM is the intermediate node number where the stiffness will be added. These nodes are numbered with the bottom being 1, so that to add a stiffness one node above the bottom, it should be added with INONUM equal 2. STADGX, STADGY, and STADGZ are the same as for -A_STIFF.

One may alter the settings of a propulsion connector with: with the option:



     -SET_PROPULSION, T_MULT, T_ANGLE, R_ANGLE

of the &CONNECTOR command. Here, T_MULT is the fraction of the maximum thrust ( -1 <= T_MULT <= 1) which will be applied, T_ANGLE is the angle that the thrust will be applied, and R_ANGLE is the angle of the rudder. Both of these angles should be -90 <= ANGLE <= 90.

One may alter a tug connector with: with the options:



     -T_FORCE, FORCE


     -T_LOCATION, ANG, DIST


     -T_DYNAMIC, PERCENT_FORCE, PHASE

of the &CONNECTOR command. The values for FORCE, ANG, DIST, PERCENT_FORCE and PHASE have the same meaning as on the commands defining the connector.

To define the special states of a foundation element for checking, one uses the option



     -SET_STATE, TYPE, MULT

of the &CONNECTOR command. Here, TYPE must be either PRELOAD or NOMINAL, and if TYPE is NOMINAL, then MULT is a multiplier which will be use in computing the unity ratios otherwise it should be omitted. See the discussion in the section on Process Post-Processing of Connectors for details on the unity ratio computation.

A launchway assembly can be activated or deactivated by using the name &LWAY for :CONN_SEL(i,j). Also, one can alter some of the settings for the assembly of launchways with the options:


     -LWA_FRICT, DYNFRC

     -LWA_ANGLE, MAX_ANGLE

Here, one selects the launchways which will have their properties altered with :CONN_SEL(.). The -LWA_FRICT option sets the dynamic coefficient of friction of the selected runners to DYNFRC, and the -LWA_ANGLE option sets the maximum angle for the first tiltbeam on the selected launchways to MAX_ANGLE (degrees). The names of the launchways are &LLEGi where i is a number assigned as the launchways were defined.

Some things with pipe assemblies can also be changed with the &CONNECTOR command. The options are:


     -PIPE_TENSION, TLOWER, TUPPER

     -DAV_LENGTH, NEWLEN,

     -MOVE_ROLLER, DX, DY, DZ,

     -LOC_ROLLER, X, Y, Z,

     -A_STIFF, STADGX, STADGY, STADGZ

     -TOP_MOMENT, YES/NO

     -ST_ADDITION, INONUM, STADGX, STADGY, STADGZ

Unless otherwise specified, :CONN_SEL should be &PIPE. The -PIPE_TENSION option sets the lower and upper bounds for the tensioner tension, TLOWER and TUPPER (bforce). The -DAV_LENGTH option changes the length of the davit elements selected by :CONN_SEL to be NEWLEN (feet or meters). If :DELEM selects the first davit element, then the entire assembly will be re-initialized and all of the lengths will be changed as when the assembly was defined. If the first element is not altered, then the selected lengths will be changed and a new equilibrium configuration of the pipe will be computed. The two options -MOVE_ROLLER and -LOC_ROLLER both result in the assembly being completely re-initialized. The first of these options moves rollers which match :CONN_SEL from their current location by an amount DX, DY, and DZ (feet or meters). The second simply defines the new location of the roller to be X, Y, and Z, (feet or meters), in the stinger body system. The last three options: -A_STIFF, -ST_ADDITION, and -TOP_MOMENT operate on the pipe exactly as they do for a simple rod connector, and were discussed above.

Winch assembly properties can also be altered with the &CONNECTOR command by using the option



     -L_DYNAMIC, ACTION, MULT, BOUND

where :CONN_SEL selects the winches to be altered. Here ACTION must be either MOTOR, BRAKE or the name of a CT_LENGTH "curve" that defines the rate of change of length (feet or meters/sec) of the line. For the first of these, the MAX_TORQUE will be multiplied by MULT and the winch motor will be turned on and the brake will be released. For the second, S_MOMENT and D_MOMENT will but multiplied by MULT and winch motor will be turned off and the brake will be engaged. For the last action, the velocity curve will be multiplied by MULT. Here, BOUND is a bound on the line length. If MULT is greater than zero (letting out line) the BOUND is an upper bound on the line length. If MULT is less than zero (letting in line) the BOUND is an lower bound on the line length.

Normally control assemblies are changed only in the time domain. One can use the -SET_PROPULSION option to set the values for statics, or use the option



     -CONTROL

With this option, the control system will attempt to counteract the static mean wind, current, and wave forces.