Define multipliers to adjust the standard DDAM shock coefficients

You can define your proprietary shock coefficients for reference acceleration and reference velocity as input to the DDAM event by entering multipliers. The multipliers adjust the reference acceleration and reference velocity that are calculated by the DDS-072-1 equations. For details about the equations and standard coefficients, see DDAM reference acceleration and velocity.

You can enter the multipliers in the Input DDAM Coefficients dialog box each time you perform the response evaluation, or you can predefine them in a text file.

Predefine the multipliers in a text file

You can predefine the shock coefficients in a text file for the response evaluation to reference.

1. Open a text editor and create a new text file.

2. Copy the text below and paste it into the text file you created. C C  *** DDAM Confidential Shock Design Value Multipliers *** C       C ---Submarine--- C ----------------------- C --Mount Location= Shell C Loading Direction=Normal to Hull C   Elastic_Design C    AF         VF     0.0        0.0 C Loading Direction=Tangential to Hull      0.0       0.0 C Loading Direction=Longitudinal to Hull     0.0        0.0 C ---------------------- C --Mount Location= Hull C Loading Direction=Vertical C   Elastic_Design           Elastic-Plastic_Design C    AF         VF             AF           VF     0.0        0.0            0.0          0.0 C Loading Direction=Athwartship     0.0        0.0            0.0          0.0 C Loading Direction=Longitudinal     0.0        0.0            0.0          0.0 C ---------------------- C --Mount Location= Deck C Loading Direction=Vertical C   Elastic_Design           Elastic-Plastic_Design C    AF         VF             AF           VF     0.0        0.0            0.0          0.0 C Loading Direction=Athwartship     0.0        0.0            0.0          0.0 C Loading Direction=Longitudinal     0.0        0.0            0.0          0.0 C C ====================================================== C  C ---Surface Ship--- C ----------------------- C --Mount Location= Shell C Loading Direction=Normal to Hull C   Elastic_Design C    AF         VF     0.0        0.0 C Loading Direction=Tangential to Hull     0.0        0.0 C Loading Direction=Longitudinal to Hull     0.0        0.0 C ---------------------- C --Mount Location= Hull C Loading Direction=Vertical C   Elastic_Design           Elastic-Plastic_Design C    AF         VF             AF           VF     0.0        0.0            0.0          0.0 C Loading Direction=Athwartship     0.0        0.0            0.0          0.0 C Loading Direction=Longitudinal     0.0        0.0            0.0          0.0 C ---------------------- C --Mount Location= Deck C Loading Direction=Vertical C   Elastic_Design           Elastic-Plastic_Design C    AF         VF             AF           VF     0.0        0.0            0.0          0.0 C Loading Direction=Athwartship     0.0        0.0            0.0          0.0 C Loading Direction=Longitudinal     0.0        0.0            0.0          0.0 This coefficients file contains your multipliers for reference acceleration (located under the AF columns) and reference velocity (located under the VF columns).

3. For the AF and VF values, enter the appropriate reference acceleration and reference velocity multipliers. You only need to modify the values for the coefficients you plan to use in your analysis. However, all other unused options must still be present in the file and set to 0.0.

4. Save the text file with a .dcf extension and make note of its location.

5. Create a new DDAM event.

6. In the New Event dialog box, select the appropriate Ship Type and Mounting type.

7. Under Response Type, select the type of deformation that is permitted due to shock. Elastic does not permit permanent deformation. Elastic-Plastic permits limited deformation.

8. From the Formulation list, select Standard.

9. In the Minimum G box, accept the default minimum acceleration 6 or type a different value. For details about how the minimum g is used in the shock spectrum equation, see DDAM reference acceleration and velocity.

10. Under Coefficient Definition Method, click By Coefficient File.

11. In the Coefficient File box, browse to the location where you saved the coefficients text file in the previous steps.

12. Click OK to dismiss the New Event dialog box.

13. Open the New Translational DDAM Excitation dialog box and define the DDAM excitation. Under Loading Type, select the direction of the shock (Vertical, Athwart Ship, or Fore and Aft). This determines the coefficients the software will use from your coefficients file.From the Components list, select the component direction for the excitation. The available components depend on the directions that were solved for when you solved the model. For example, if the enforced motion location was defined in the X and Y directions, only X and Y will be available for selection as the component. The direction component you select should correspond to the Loading Type direction.

14. Perform the response evaluation.

15. Click OK. When you perform the response evaluation, the software uses the coefficients in the .DCF file that correspond to the Loading Type you specify in the New Translational DDAM Excitation dialog box when you create the excitation.

Define the multipliers during each response evaluation

Alternatively, you can enter the reference acceleration and reference velocity multipliers each time you perform the response evaluation. The multipliers are not stored after the software completes the evaluation calculation.

1. Create a new DDAM event.

2. In the New Event dialog box, under Coefficient Definition Method, click Input Manually.

3. Follow steps 6-9 from the above procedure.

4. Click OK to dismiss the New Event dialog box.

5. In the New Translational DDAM Excitation dialog box, define the DDAM excitation. Under Loading Type, select the direction of the shock (Vertical, Athwart Ship, or Fore and Aft). From the Components list, select the component direction for the excitation. The available components depend on the directions that were solved for when you solved the model. For example, if the enforced motion location was defined in the X and Y directions, only X and Y will be available for selection as the component. The direction component you select should correspond to the Loading Type direction.

6. Perform the response evaluation. The Input DDAM Coefficients dialog box appears.

7. Type a unitless multiplier for the reference acceleration coefficient (Coefficient AF) and reference velocity coefficient (Coefficient VF).Note: The direction of the excitation (fore/aft, athwartship, or vertical) is determined by the Loading Type you choose in the New Translational DDAM Excitation dialog box when you create the excitation.

8. Click OK to dismiss the Input DDAM Coefficients dialog box.

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