DDAM reference acceleration and velocity

During the response evaluation, the software uses the following equations to calculate the reference acceleration and reference velocity for each mode.

Reference acceleration

Reference velocity

where W is modal weight in kips; AA, AB, AC, AD, and AF are the coefficients for acceleration; and VA, VB, VC, and VF are the coefficients for velocity.

When you perform a response evaluation, using the reference velocities and reference accelerations, the software calculates the shock design values of acceleration for each mode using:

where D is the shock design value of acceleration, Vo is the reference velocity, Ao is the reference acceleration, and ω is the natural frequency (in rad/sec). gmin is the user-specified minimum acceleration (Minimum G).

User Defined Formulation

You can use the User Defined Formulation to enter your own custom coefficients for the AA, AB, AC, AD, AF, VA, VB, VC, and VF terms. For steps, see Define custom DDAM shock coefficients.

Standard Formulation

You can use the Standard Formulation to enter multipliers that the software applies to standard reference values (listed in the following table) that follow the DDS-072-1 specification. For steps, see Define multipliers to adjust the standard DDAM shock coefficients.

Ship type and mounting location	Standard Formulation Coefficients	Standard Formulation Equations
Submarine, all mounting locations	AA=10.4AB=480AC=20AD=20VA=20VB=480VC=100AF=user-specified multiplierVF=user-specified multiplier
Surface ships, shell and hullThis includes items mounted on the main structural members of the ship, including structural bulkheads and structural bulkhead stiffeners below the main deck, and shell plating above the waterline.	AA=20AB=37.5AC=12AD=6VA=60VB=12VC=6AF=user-specified multiplierVF=user-specified multiplier
Surface ships, deckThis includes items mounted on the main deck and above, and on decks, platforms, and non-structural bulkheads below the main deck.	AA=10AB=42AC=6AD=6VA=60VB=12VC=6AF=user-specified multiplierVF=user-specified multiplier

How do I

Create an event

Clone an event

Copy an event from one Response Dynamics solution process to another

Set up sequential transient events

Define multipliers to adjust the standard DDAM shock coefficients

Define custom DDAM shock coefficients

Learn more

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DDAM reference acceleration and velocity, Simcenter 3D 2021.1 Series

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