ETABS - Axial load in braced frame beams

[tpsk]

Hi all,

I was reading this old post that dealt with axial loads in beams part of braced frames.
[URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=235107[/url]

In my model I am using a semi-rigid diaphragm to capture the axial loads in beams due to eccentric braced frames, but I would like this axial load to be carried by the steel only and not shared with the concrete slab...
I tried setting the membrane stiffness of the slab to 0.01, but I don't seem to be getting the actual axial load I would expect. Moreover, I am not confident at all with how the seismic loads are distributed in a diaphragm for which I set the axial stiffness to 0.01.

Does anyone have any idea on this?
Thanks a lot for your help.

 

[slickdeals]

You could try using a plate element (no in-plane stiffness). In the past, I have used f11=f22=f12=0.01.

As a matter of fact, ETABS recommends using this in the staggered truss module in order for the truss to carry all the load with no benefit of composite action.

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN

 

[tpsk]

I am using a metal deck section for floors with f11=f22=f12=0.01 also.
I am just wondering how accurate the load distribution in my diaphragm is once I have set that membrane stiffness to 0.01...

Do you have any experience on that?
Thanks a lot