Seismic analysis

[Ehsan1199]

I got the weightUsed from Auto Seimic UBC97 in ETABS and it is different with what I got from the sum of diaphragm mass data?

I do not know what is the problem?

 

[saeedHR]

How much is the difference. some times there are some parts that are not connected to the floor diaphragms. their weight is considered in Auto seismic loads but not in diaphragm mass. its netter to compare it with the story mass.

 

[Ehsan1199]

Dear Saeed

tanx for reply.
I have checked it and the difference is about 30000 KN which is really too much.
How can I check whether they are connected or not to the diaphragm.

 

[Ehsan1199]

How can I get the story mass from ETABS?

 

[nicus]

Display/Building Data/Mass Data/Diaphragm Mass Data - This are the ones from the mass source, you have to multiply the mass for the gravity.

Display/Building Data/Materials/Material list by story - you get the masses from each stories

 

[slickdeals]

Sometimes if your wall is meshed between floor diaphragms, then its mass is not captured in the floor diaphragm mass data.

I forget if it happens when you internally mesh the wall or if you explicitly mesh it. But it does happen if you have mesh points that lie between 2 floor diaphragms.

The best way to compare is to use point mass values.