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Unbraced length for Wood Compression Brace

Unbraced length for Wood Compression Brace

Unbraced length for Wood Compression Brace

(OP)
The attached sketch shows an existing diagonal wood member, 2x8, that extends from the top of an existing masonry pier to an existing floor joist above. There are a number of such braces to carry the wind load from the first floor down to the piers. The wind load acts on the exterior wall above the first floor.

My question is what should be used for the unsupported length for the design of the diagonal brace?

Should it be the 77" length (see attached sketch) which is the distance between the intersections of the centrelines of the members, or should it be the 67" which is the clear distance? Or should it be something between these values to allow for the fact that the nails fastening the members will not be right at the edge?

RE: Unbraced length for Wood Compression Brace

Centre to centre with K=1 for a new design. If it's existing and you're hungry, you could throw some screws in there and probably call it K = 0.7 about the weak axis. I can't view the sketch so I had to make some assumptions about the nature of the connection.

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: Unbraced length for Wood Compression Brace

(OP)

Kootk - I am curious as to why you cannot view the sketch. Did you click on the line at the bottom that has a paper clip image and starts http? It took me a while to make that sketch.




RE: Unbraced length for Wood Compression Brace

Eh, take no stock of it. I'm on my phone in Jamaica.

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: Unbraced length for Wood Compression Brace

(OP)
ok, not a problem

RE: Unbraced length for Wood Compression Brace

IMHO, there is no exact answer. I would say 72" to get back to the nailed area and work with that.

Forgive me, but I have to chuckle at the "precision" of your sketch... distances to three decimal places (67.211" to 77.191"). On a slide rule that would be 67.2" to 77.2" and even that would be way too precise an answer.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Unbraced length for Wood Compression Brace

Don't drink too much of that Jamaican Rum, KootK and go easy on the Ganja; enjoy! Irie, man!

BA

RE: Unbraced length for Wood Compression Brace

Considering the brace is loaded eccentrically, I would suggest using the c/c distance.

BA

RE: Unbraced length for Wood Compression Brace

(OP)
To SlideRuleEra - I am from slide rule era too, so I appreciate your comment. The sketch is not accurate to 3 decimal places; it's just that I find it seems to be easier to mark off the distances in Bluebeam when I set it to greater accuracy.

To BARetired: ok, you always seem to have wise advice, so I will use c/c but then of course the slenderness ratio > 50 and the capacity is therefore zero. I am likely to get some push-back from the contractor's engineer whom he hired after I pointed out a number of things built wrong.

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