Slow Calculations/Results Modal Analysis

[Anonymous]

Hi,

I'm modeling a long building (36x140 m2) and when I run the modal analysis it takes quite a long time calculating. It also says that mass participation is not satisfactory. When I try to see the modes of vibration it gets even slower and I dont get to see them.

Structure has 8 slabs, bottom 2 slabs are simply supported to portray the underground walls. Beam is just on contour of slabs, and slab is simply supported on internal columns. I used emmiters above columns for a better meshing option (High number of nodes). 

RT file is quite large aprox. 80MB.

Not sure if its normal to take so long due to being a large building, or I am doing something wrong.

Thanks in advance!

File to large for attachment. 

[Rafacascudo]

1. Save the file with a different name and without results(save as) , and then attach it here. Zip/rar it if it is still too big.

[Anonymous]

Sorry, forgot to delete the part where it says file to big for attach. Its zipped in attachment already and I also did it the way you said.

Thanks.

[eear_gabriel]

Rafael, do you recommend any tutorial for learning Robot?

[Simau · Accepted solution]

Hi @Anonymous

you have not converted cases en masse. Case 8 that you tried to convert does not contain any load.
You also neglected the density and you did not convert case 10.
I run your model by converting only the 10 selfwiegth case. And it works fine.
As you have 2 fixed floors on 8 levels, you will never be able to vibrate the 2 lower levels, so 25% of non-convertible masses.
For the message "missing eigenvalues", just clik "No"

[Rafacascudo]

Well , some 17 years ago I learned Robot by myself consulting the manuals ,help files  ,and in last case, emailing the support Guys( the same that are here tody)with my doubts .

Now there are lots of sources . Search the fixed threads especially

https://forums.autodesk.com/t5/robot-structural-analysis-forum/robot-vault-lots-of-information-for-n...

https://forums.autodesk.com/t5/robot-structural-analysis-forum/latest-updates-new-knowledge-network-...

The official RSA webinars on Build your Robot Structural Analysis IQ - YouTube 

A good book on https://www.amazon.co.uk/s/ref=dp_byline_sr_book_1?ie=UTF8&text=Ken+Marsh&search-alias=books-uk&fiel...

And of course  ,now we have this forum which ,in my opinion , is the best soucefor easy and fast RSA knowledge .

By far the best among all Structural software packages in the market

[Anonymous]

Thanks for the help.

Ive considered just case 10 for mass conversion and I have not considered the "disregard density" option. When I run it on my laptop it takes about 25 mins for the full process (verification and analysis). I started the calculations at 20h49 and got through the whole process at 21h13. Does that seem reasonable? 

The modes I am retrieving are different from the ones you posted. Not sure what it is I'm missing here. 

[Simau]

@Anonymous

looking at your results, we get the same mobilzed masses.

Frequencies are slightly different.

Did you get warning about "missing eigenvalues" and what did you reply: "yes" or "no"?

[Anonymous]

"No" as you said. 

How long does it take you to run the calculations?

[Simau · Accepted solution]

Yes

calculation time is reasonable, 24 min also here.

You may reduce time by increasing mesh size, you have 161280 finite elements and 902088 degres of freedom

[eear_gabriel]

Cheers mate..I`ll definitely have a look at these sources..thanks again