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Development length cog - AS 3600 3

LR11

LR11

Structural
Sep 13, 2001
169
Hi, getting different opinions on this, but wanted to confirm if reading of AS 3600 is correct.

For a bar in tension, let's say 1000mm (Lsy.t) is needed to achieve full development, from formula Lsy.t = Lsy.tb = 0.5.k1.k3.fsy.db/k2.√fc' ≥ 0.058.fsy.k1.db

If there is a cog, then is approximately 500mm (0.5Lsy.t) needed to achieve full development?
So effectively half the space is required?
 
Solution
icebloom
Correct, provided there is a cross bar in the corner of the cog. Without a cross bar you can only take the bar stress to 400MPa as per the clause in chapter 13.
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Correct, provided there is a cross bar in the corner of the cog. Without a cross bar you can only take the bar stress to 400MPa as per the clause in chapter 13.
 
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Solution
Thanks for confirming icebloom.

What if you had a straight portion of 0.25Lsy.t, what would the overall contribution be?

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What if you had a straight portion of 0.25Lsy.t, what would the overall contribution be?

Without a transverse bar the cog can develop 0.5Lsy,t=Lsy,t*400/fsy. You would then get another 0.25Lsy,t from the straight extension.
So for fsy=500MPa you could get (0.4 +0.25)Lsy,t =0.65Lsy,t. [AS3600 13.1.2.6]. Well that's my interpretation.

If you're having trouble getting anchorage the first thing I would suggest is to use smaller bars. Next would be headed anchors and these don't require a transverse bar.

The code does not specify where the transverse bar must be located which seems an omission.
 
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13.1.2.5 Development length around a curve

Tensile stress may be considered to be developed around a curve if the internal diameter of the curve is 10db or greater.
 
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