Modal mass Percentage & different elevation

04-Unexpected behaviour/errors
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Yasmin250
Posts: 1
Joined: 05 Nov 2020, 17:10

Modal mass Percentage & different elevation

Post by Yasmin250 »

hey Everyone;

I built a model with seismobuild, the building is two story build with underground story at part of entire area!
I am facing two problems:

1- how to overcome the different elevation of the foundations, since part of the building has an underground story and the rest are starts at ground level?
I tried building columns, but i guess it's not the best solution! In addition i don't want to add massive elements resulting a larger mass for earthquake forces, any suggestion?

2- Eigenvalue Analysis the building didn't reach over 50% of the mass, it has 22 modes!

any Idea what is the problem? or what should i check to make sure i am not doing something wrong,
I applied the loads on the slabs
I checked the reinforcement

I could send the model, if anyone has time to take a look

I appreciate any help or idea.

Thanks
Yasmin
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seismosoft
Posts: 860
Joined: 06 Jul 2007, 04:55

Re: Modal mass Percentage & different elevation

Post by seismosoft »

1. In the Building Modeller you can choose whether a column at the lowel level or in upper levels is supported or not through the 'restrained' property. Furthermore, you may change the foundation level through the Foundation Top level parameter
2. From the Main Window of the program go Toolbar>Analysis Parameters>Advanced Settings>Eigevalue and increase the number of eigenvalues sought

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