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# Obtaining centre of rigidity in Etabs

## Obtaining centre of rigidity in Etabs

(OP)
CSI knowledge Base tells This:

""During analysis, ETABS automatically calculates this coordinate for each floor diaphragm. The diaphragm assignment must be present in the model. Center of rigidity and center of mass are then displayed by selecting Display > Show Tables > Analysis > Results > Structural Results > Centers of Mass and Rigidity > OK""

But the option 'Centers of Mass and Rigidity' is not there inside 'Structural Results' in Etabs.

Ravi K

### RE: Obtaining centre of rigidity in Etabs

Do you have your diaphragms set to 'rigid'?

### RE: Obtaining centre of rigidity in Etabs

(OP)
Forgotten to set the diaphragm rigid. Now it is showing the option 'Centers of Mass and Rigidity.

Thanks..

How can we increase the eccentricity in the model ?

if eccentricity = 1.5*structural + 5% accidental.

### RE: Obtaining centre of rigidity in Etabs

Go to Analyze > Set Load Cases To Run

Is "Calculate Diaphragm Centers of Rigidity" checked?

### RE: Obtaining centre of rigidity in Etabs

(OP)
Yes i did it @DETstru,

Now it is showing the option 'Centers of Mass and Rigidity.

Thanks

How can we increase the eccentricity in the model ?

if eccentricity = 1.5*structural + 5% accidental.

### RE: Obtaining centre of rigidity in Etabs

You can manually adjust the eccentricity of each floor in the Response Spectrum Load Case Data.
That's under Define > Load Cases
(I'm assuming you're running a response spectrum case)

### RE: Obtaining centre of rigidity in Etabs

(OP)
@DETstru

No, I am not running a response spectrum case. I am only applying lateral load calculated by seismic coefficient method at the frame joints. I wanted to increase the eccentricity value for safer design. But i could not find the the option in Etabs.

### RE: Obtaining centre of rigidity in Etabs

If you are referring to user loads you may find the eccentricity field on your bottom right corner when you hit modify load pattern

If you meant code static loads it should be on the top left corner

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