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Deflection Interaction on Structure

Deflection Interaction on Structure

(OP)
I have been trying to wrap my head around how the deflections interact in the following problem I am presented with.

A structure with masonry endwalls, roof diaphragm, and portal frames has been eluding me. As seen in the attachment, I envision the wall bending as a simply supported beam while transferring the load to the roof diaphragm. This in turn, will cause the roof diaphragm to deflect as a beam with maximum deflection seen at the midspan. The roof diaphragm then transfers the load to the sidewalls and into the portal frames which also deflects.

How would one design the masonry wall for deflection? The only information I can find is per strength design procedures in ACI 530 and the deflection is limited based upon midheight deflection for a simply supported condition. I would think you would start by designing the steel portal frame for deflection and work backwords, but how does this deflection interact with the other deflections that are occurring.

RE: Deflection Interaction on Structure

While I get what you're saying, I think that most engineers would just check the mid-span deflection of the wall assuming that it was simply supported top and bottom and leave it at that.

To answer your specific question, a rigorous determination of lateral wall deflection would go something like this:

1) Find drift at top of moment frames.
2) Find diaphragm deflection at plan location of interest.
3) Find wall deflection at vertical location of interest.
4) Add up one through three.

This is pretty much just what you've described above.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Deflection Interaction on Structure

(OP)
I do agree with your opinion on the typical approach taken by most engineers. The reason I am concerned with this is due to having stack bond construction for the masonry wall. I was mainly unclear if all three deflections could be added together to arrive at the total deflection.

RE: Deflection Interaction on Structure

Stack bond... barf. Particularly where you'll be introducing horizontal curvature into the top of the wall. Still, nothing new under the sun here.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

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