# Re: problem with ETABS

• To: seaint(--nospam--at)seaint.org
• Subject: Re: problem with ETABS
• From: "Michael Bryson" <mbryson(--nospam--at)bnflinc.com>
• Date: Tue, 04 Apr 2000 11:24:28 -0700
```ETABS allows you to add a torque to your diaphragm and do load
load distribution for each floor level:
Txi = Fxi * eyi
where Fxi is the force at level i for the x-direction
eyi is the 5% eccentricity at level i in the y-direction
Tyi = Fyi * exi
where Fyi is the force at level i for the y-direction
exi is the 5% eccentricity at level i in the x-direction

Use these torques as separate load cases, for example:
LC1 = Seismic in x-direction with no eccentricity
LC2 = Seismic in y-direction with no eccentricity
LC3 = Torque Txi only for y-direction eccentricity
LC4 = Torque Tyi only for x-direction eccentricity

The load combinations you would have to look at for walls and columns
are:
Comb1=  |LC1| + |LC3| + LC6         max. tension for x-direction seismic

Comb2=  -( |LC1| + |LC3| ) +LC5    max. compression for x-direction
seismic
Comb3=  |LC2| + |LC4| + LC6         max. tension for y-direction seismic

Comb4=  -( |LC2| + |LC4| ) +LC5    max. compression for y-direction
seismic
And for beams:
Comb5=  |LC1| + |LC3| + |LC5|    max. moment for x-direction seismic
Comb6=  |LC2| + |LC4| + |LC5|    max. moment for y-direction seismic

You could do all this for dynamic analysis as well, but there are some
options.

HAKAN EZCAN wrote:

> hi all.., i have a question to all who especially use
> etabs program , we are using the structural analysis
> program that own written about 20 years, i want to use
> etabs but im very new on it and i dont know yet how to
> fix that : in our  code we must check the building for
> quake loads when they effect center of gravity of
> slabs and 0.05 percent eccentricity + and - for each
> directions x ,y so we design the building for most
> significant forces of total 12 load cases (3 of each
> direction x,y -x,-y ) im workin on it, can any body
> tellme how to calculate that on etabs , because etabs
> has only 3 lateral load cases as ive seen
> thanks :)
>
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```