equivalent lateral force model

[rodainnajjar1229]

Dear Sir
first question
Kindly find attached file

http://www.4shared.com/zip/TcRbjMkQ/Robot.html
i have model with seismic ( equivalent lateral force model )
when  i checked effective seismic weight from calculation note :
W =52167607 KG
but total mass ( result-advance-model analysis) =32063407 kg
secand question
i have to know when i insert load to mass conversion  i choose  add mass to global mass or
 model or dynamic mass

Best Regards

[Artur.Kosakowski]

Could you upload the file on another service please? I'm not able to download it. Thank you.

[rodainnajjar1229]

http://www.filemail.com/d/fydbuuyohucfutf

[Artur.Kosakowski]

In the current version of Robot it is not possible to exclude density from being taken into account for the Lateral force method (see http://forums.autodesk.com/t5/Autodesk-Robot-Structural/NBCC-Seismic-Equivalent-Static-Method/td-p/3...

In your model the self weight for the lateral force method is doubled (one time being included automatically and the other time as converted case 1)  whereas for the modal analysis it is taken into account only one time (from the conversion of case 1).

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[rodainnajjar1229]

In the current version of this Robot how i can insert only self weight for part of structure to mass conversion in dynamic analysis i see it include all self weight automatic to mass in seismic analysis+load to mass conversion in calculate base shear

[Artur.Kosakowski]

If you mean the response spectra analysis then mark disregard density in the modal analysis parameters, create a load case that contains self weight for selected part of the structure only and convert it into the mass.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[rodainnajjar1229]

Dear Sir
I mean when i use seismic analysis (not spectral )
reagards

[Artur.Kosakowski]

The seismic analysis in Robot is based on the response spectra approach. This type of analysis and the spectral one are the same in their principles. 

Is this the analysis you mean writing dynamic seismic analysis ?

[rodainnajjar1229]

dear sir
i created a load case that contains self weight for selected part of the structure only and convert it into the mass. but no solution
kindly find attached file pic1.2.3 in last post
regards

[Artur.Kosakowski]

Attach your model please.

[rodainnajjar1229]

kindly find attached file 

regards

[Artur.Kosakowski]

Which of these two self weight cases should include the whole model and which should be converted for dynamic analyses?

[rodainnajjar1229]

dear sir
kindly find attached file
1- i define two self weight  for top and bottom like your photo ( sw on part of model.png ‏)
2- i insert  only self weight for top to load to mass conversion

regars

[Artur.Kosakowski · Accepted solution]

The value in the calculation note in Robot 2013 incorrectly includes self weight but  the mass used for calculations is correct. The value in the note has been corrected for Robot 2014.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[rodainnajjar1229]

thank you

[Artur.Kosakowski]

Hi @rodainnajjar1229 

The option of neglecting self-weight for this type of analysis was introduced RSA 2020.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.