Structural X-Bracing

Structural X-Bracing

Postby oring1981 » Sun Mar 10, 2019 3:56 pm

Hello All-

I am retaking PPD AGAIN in a week and I have been studying for a good three months and I am still looking for some good examples of where to find X-Bracing placement. I would really use any ones help on this. The only place someone has told me to look is in Kaplan and I have yet to find anything in their. Please Help.
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Re: Structural X-Bracing

Postby Anob » Mon Mar 11, 2019 3:35 am

I found good examples in “Building Structures” by Ambrose (there’s a free pdf floating around)
and “Statics Strength and Mateirals”.
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Re: Structural X-Bracing

Postby tua97770 » Mon Mar 11, 2019 7:37 pm

Anob wrote:I found good examples in “Building Structures” by Ambrose (there’s a free pdf floating around)
and “Statics Strength and Mateirals”.


I am testing this week, do you know which chapter I can find "x" bracing topics in Ambrose?

Thanks!
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Re: Structural X-Bracing

Postby sofiasalvat » Wed Mar 27, 2019 1:36 pm

Did you find any good references? Looking for guidance on this as well.
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Re: Structural X-Bracing

Postby kranjerj » Sun Mar 31, 2019 3:15 pm

Not sure if this is exactly what you're looking for but I've found the FEMA earthquake pdf to be pretty good (chapters 4, 5, & 7)
https://www.fema.gov/media-library-data ... mplete.pdf

The chapters aren't terrible to skim. lots of diagrams.
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Re: Structural X-Bracing

Postby architectco » Mon Apr 01, 2019 4:37 am

from what i understand the bracing is for lateral stability of the building and is generally centrally located in steel frame walls, on two opposing walls and stacked directly on top of each other from first floor to top floor.

although for smaller buildings say one floor ideally should be centrally located but i am not completely sure and should be looked up may be located a-centrally
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Re: Structural X-Bracing

Postby Anob » Mon Apr 01, 2019 6:11 am

It really sucks that with all these resources there isn't a definitive answer. I found this discussion to be helpful, especially Benjamin's last comment. Also found this in "Building Structural Illustrated"
https://are5community.ncarb.org/hc/en-u ... ce-framing
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Re: Structural X-Bracing

Postby ccolley12 » Thu Apr 04, 2019 12:49 pm

Like many aspects of design, there is no singular correct answer to this. There are more efficient and less efficient ways to resist lateral loads.. so the way a specific question is worded is important.
First, X bracing is there to resist lateral forces... wind and seismic are the primary lateral forces that act on a building. Seismic is often the strongest load and so it typically governs the lateral design and thus often times people refer to X bracing as seismic bracing... but really, it is lateral bracing. There are many types of lateral bracing systems... X bracing refers to the shape of the diagonal braces within a steel frame... some engineers refer more generically to these frames as simply Braced Frames (BF). They could be chevron shaped, K shaped, etc. In some light structures, the bracing is actually steel rods, though they are typically HSS or WF steel shapes. The diagonal members, regardless of shape or orientation are all designed to be in tension and thus they often are paired as an X, that way depending on which direction the lateral force is coming from, one of the members will always be in tension.

In terms of placement, the number and location are largely dependent on 2 main factors; the geometry (shape) of the building footprint and the type/strength of the lateral load itself. Assuming a mostly rectilinear building and a desire to use the most efficient system, frames should be placed at the building perimeter, on all 4 sides and roughly in the middle of each side. In the case of a multi-story building, the frames should be aligned floor to floor.

If the building footprint is irregular, I typically try to break it into squares/rectangles and then follow the rules above as best as one can. This will get you close... close enough that a structural engineer won't totally laugh at you!
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Re: Structural X-Bracing

Postby greek22 » Wed Apr 17, 2019 6:09 am

Hey anob - is this the book you're referencing? If so, do you recommend this book for PPD? I have Building Code Illustrated and Building Construction Illustrated.
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Re: Structural X-Bracing

Postby Anob » Wed Apr 17, 2019 6:33 am

I do recommended it. It has a lot of great illustrations. Great combination with 4.0 Kaplan structures.
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