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# Response Spectrum Analysis, defining input

## Response Spectrum Analysis, defining input

(OP)
Hello, started using ABAQUS three weeks ago for an undergrad project.

I'm looking to perform a response spectrum analysis and dynamic explicit analysis on an assembly imported from Solidworks. I was expecting to be able to define the input (acceleration as a function of frequency) at the load step, but have been unable to locate where to define the spectrum?

After I do this, I hope to be able to apply this acceleration excitation to three fixed surfaces and track both the nodal stresses and maximum response accelerations as functions of frequency. I do not know how to apply my acceleration input to these specific locations.

Thanks!

Best regards,
--Dave

### RE: Response Spectrum Analysis, defining input

Dave,

an explicit analysis is typically done in the time domain. As far I know its not possible to work with acc. vs. frequency in Abaqus explicit. Acc. vs. time is required.

If your excitation is harmonic I recommend to run a steady stat dynamic analyis with abaqus standard. Find a frame below. Its with basemotion excitation

CU

:
:
:
*NSET,NSET=fix
117,118,119,120,129,130,139,140,1460,1461,1462,1463,1464,1465,1466,1467
:
:
:
*AMPLITUDE,NAME=XI
34.7937, -1647.59, 35.936, -467.465, 38.257, 2279.74, 39.919, 1263.25,
:
:
:
*AMPLITUDE,NAME=XR
34.7937, 726.63, 35.936, 1938.45, 38.257, 255.67, 39.919, -1993.55,
:
:
:
*AMPLITUDE,NAME=YI
:
*AMPLITUDE,NAME=YR
:
*AMPLITUDE,NAME=ZI
:
*AMPLITUDE,NAME=ZR
:
**
** STEP 1
**
*STEP,NAME=FREQUENCY
*FREQUENCY,EIGENSOLVER=LANCZOS
10,,250.0000
**
** BOUNDARY
**
*BOUNDARY,TYPE=DISPLACEMENT
fix,1,3,1.000000
**OUTPUT,FIELD,VAR=ALL
*END STEP
**
**
*STEP,NAME=ACC
35.,168.,20,3
*MODAL DAMPING,MODAL=DIRECT
1,10,0.0176
*SELECT EIGENMODES,GENERATE
1,10,1
*OUTPUT,HISTORY,VAR=PRESEL
*NODE OUTPUT,NSET=POST,VAR=PRESEL
TA,
*END STEP
**
**
*STEP,NAME=STRESS
35.,188.,2,
*MODAL DAMPING,MODAL=DIRECT
1,10,0.036
*SELECT EIGENMODES,GENERATE
1,10,1
*OUTPUT,FIELD,V=ALL, FREQ=1
*ELEMENT OUTPUT,VAR=ALL
*END STEP

### RE: Response Spectrum Analysis, defining input

(OP)
Hi Pam,
Thanks for the tip regarding abaqus explicit. I had actually hoped to have a time history of some kind, but was only provided with the acceleration content as a function of frequency. The content represents (I believe) a shock transient over a moderate amount of time.
The base motion input should be quite useful in representing my loading - thanks!!

With regards to my other novice question, can anyone direct me to where I would input an acceleration spectrum in order to do a response spectrum analysis? I'm mostly a GUI user at this point, and everytime I attempt to update the keyword file of the database it gets re-written prior to submitting the job.

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