6-Story Braced Frame Analysis

[teckert]

I am doing an Seismic Analysis on a 6-Story inverted Chevron Brace system, similar, to the Sabelli Report if anyone is familiar with that? The question i have is why did they have to include a "dummy column" - non Braced Frame Column to the system. As you can see from the attachment.

If anyone has an answer, please respond as soon as you can.

Thanks,
Tim

 

[Lion06]

Is it possible the "dummy column" is really the side view of a braced frame for the perpendicular direction? How do you know it's a dummy column?

 

[SteelPE]

I am not familiar with the specific report you are talking about but the “dummy column” could be placed in the computer model to account for the effects of “leaner” columns in a pdelta analysis? This would require linking the dummy column to the braced frame at each level which your sketch doesn’t know.

Maybe if you posted a link to the report you would get more accurate responses.

 

[priya15]

Teckert:

I think you are talking about dummy column as in "zipper column" in the V bracing system. This was developed by Dr. Leon from Georgia Tech University. I attended a seminar and he said he did some studies that showed that dummy column (zipper column, thats what he called) would help in the overall strength of the system. I do not have any report to send you. But I do have his e-mail address: rleon@ce.gatech.edu
He is avery nice professor and I am sure will be able to answer your questions. Please do share back with us your findings.

 

[JoshPlumSE]

I don't think priya15 was able to view the picture that was attached to the original poste. Because, the "dummy" column in the picture is clearly NOT a zipper column.

I agree with SteelPE that it is likely meant to represent the "leaner" columns that contribute to the P-Delta effect on the braced frame.

 

[sandman21]

The "dummy" column accounts for the gravity columns contribution to the lateral stiffness of the structure. Not sure which report you are referring to but if is the report about buckling restrained braces frames, the section that talks about it can be found on page 8.

 

[csd72]

Fascinating,

Has anyone ever used this method for wind analysis?

 

[WillisV]

Yes - its just a method of accounting for leaner columns on P-delta for systems where you don't model the entire gravity system along with the lateral system. Also called a "ghost" column method. It was more popular before commercial software like RAM let you easily develop a model for the entire building as opposed to just looking at 2-d frames.

 

[priya15]

Sorry, I saw the attachment it looks wierd. If I assign just a column as a lateral member and do not assign any beams framing into it as a lateral member, I wonder how computer model would analyze it. What is the member that can actually transfer lateral loads to the column in such a case for a proper load path? I have never done this before nor even heard of others who did it. Curious to know what you do further.