Product(s):	SACS
Version(s):	ALL
Area:	Fatigue

 

Community Query:

Hello Bentley

I'm performing a Time History fatigue analysis due to sea-ice loading (these are inputted as external load, not generated by sacs).

The external loading due to sea-ice creates 35000 load cases in each CSF file, I would like to call these 35000 load cases in the fatigue input file to calculate fatigue results by using rainflow counting.

However, I am willing to call 8 CSFs in one ftginp i.e. one run. Then, SACS will generate internal load case = 35000* 8 = 280000 cases. 

I am not sure about the capacity of SACS to perform this kind of large analysis.

could you provide advice?

 

Recommendation

Until now, we haven't had reports about SACS issues in fatigue loads. In fact, the software could process all loads you wish input processing. The only setback that you may face is the time spent for the postprocessing of these ones Very large fatigue analyses are supported in principle; limitations are practical (runtime, memory, disk I/O), not solved.

If performance or stability issues occur, the recommended workflow is to split the fatigue analysis into multiple runs. And Fatigue damage should be progressively accumulated by reusing the damage output file from the previous run (e.g., run each direction separately and chain damage files).

This staged approach is currently the supported and reliable method for large-scale fatigue analyses.

here you have the procedure to follow

• 1.- Run Static Analysis to get the Super Element
• 2.- Run Dynamic Analysis to get the dynmod.DYN and dynmas.DYN files
• 3.- Run every wave response separately for each direction (000, 022, 045 ,, etc)
• 4.- Run spectral fatigue address 000 separately, requiring SACS to create the output damage file
• 5.- Run Spectral fatigue for direction 022 adding up the output file created from 000 direction
• 6.- Run Spectral fatigue for direction 045 calling the output file created from 022 direction
• 7.- Run Spectral fatigue for direction 067 and call the output file created from 045 direction
• 8.- Followed this procedure until finish all runs

We know that following this workaround it could take some time, but this is the only one way in which you can fatigue analysis considering all loads

Regards