ddaspec

SpectrumOptions.ddaspec(keyref='', shptyp='', mountloc='', deftyp='', amin='', **kwargs)

Specifies the shock spectrum computation constants for DDAM analysis.

Mechanical APDL Command: DDASPEC

Parameters:

keyrefint or str

Key for reference catalog:

• 1 - The spectrum computation constants are based on NRL-1396 (default). For more information, see Dynamic Design Analysis Method

shptypstr

Select the ship type:

• SUBM - Submarine

• SURF - Surface ship

mountlocstr

Select the mounting location:

• HULL - Hull mounting location. These structures are mounted directly to basic hull structures like frames, structural bulkheads below the water line, and shell plating above the water line.

• DECK - Deck mounting location. These structures are mounted directly to decks, non-structural bulkheads, or to structural bulkheads above the water line.

• SHEL - Shell plating mounting location. These structures are mounted directly to shell plating below the water line without intervening foundations.

deftypstr

Select the deformation type:

• ELAS - Elastic deformation (default)

• PLAS - Elastic-plastic deformation

aminstr

Minimum acceleration value. It defaults to 6g, where g is the acceleration due to gravity.

Notes

The excitation along one of the fore and aft, vertical or athwartship directions is required to calculate the spectrum coefficients. Issue the sed command before issuing ddaspec. For example, if you want to apply the excitation along the fore and aft direction, you should specify SEDX = 1.0 on sed. Similarly, for excitation along vertical or athwartship direction, specify SEDY = 1.0 or SEDZ = 1.0, respectively, on sed.

addam and vddam may alternatively be used to calculate spectrum coefficients.

In order to perform a DDAM spectrum analysis using a units system other than BIN (default), you must specify the units system complying with the mass and length units of the model using the units command. Issue the units command before defining the shock spectrum computation constants ( ddaspec ). The DDASPEC command is not supported with the user-defined units system ( Label = USER on units ).

This command is also valid in PREP7.