Hi
With respect to the response spectrum analysis, please would someone clarify how to combine responses for x,y and z directions:
While inputting the spectrum with dyrinp file, do I need to specify the spectrum in 1 direction while setting the spectrum in other two directions as 0.0! Then repeat this for other two directions? Thus while doing this I will be creating 3 dyrinp files for spectra in x,y and z directions (therefore 3 common solution files!)! Subsequently, would I be correct in my approach to use combine module to create 3 load cases to combine responses using SRSS method? This will be achieved using leading response file as primary file ‘P’ while second file as secondary ‘S’ and third file as ‘3’ –repeat this for all 3 directions while changing primary and secondary files as below:
Combined loading 1: x response (P), y response (S), z response (3)
Combined loading 2: y response (P), x response (S), z response (3)
Combined loading 3: z response (P), x response (S), y response (3)
Please advise.
SACS uses SRSS to combine modal responses to spectral loading. Refer to Section 3.1.3 of the Dynamic Response manual for more information.
Hi aaa123,
I understand that your question is
Do you need to split SPLOAD command to be 3 commands for X Y and Z.
The answer is "NO NEED".
You can make it the same line. Directional spectrum will be combined by using SRSS method by SACS default. You no need to specify SRSS for directional combination, if you put all Spectrum in the same SPLOAD command.
Nonetheless, if you still need to split into 3 SPLOAD commands. It is not wrong. Btw, you no need to create 3 dyninp. You can repeat SPLOAD in the same dyninp.
Finally, you will have only 1 CSF which you also can combine the solution inside that CSF for directional combination. In your combine input file, all will be "P".
If you go this way, you also have to combine your seismic solution with static load by using 'PRSC' and 'PRST' at the end.
Geoff, please correct me. If I understand something wrong.
Regards,
Kasiphon
Answer Verified By: Geoff McDonald