AS3600 - Development length around a curve 1

[Vito11]

Hey folks,
Can someone shed some light on clause 13.1.2.5 Development length around a curve?
Does this apply to horizontal bars at the corner of shear walls? Section 14 shows the bend for boundary element discontinuity only.
How does this match up with the closed fitments?
Which other standards require this?

 

[Just Some Nerd]

Snapshot from that section of the commentary for you, if that helps.

In practice I'd always stick to sharp bends (i.e. your picture on the right) rather than curves, I don't get the feeling curves are as good for restraining those corner bars and curves seem a lot more annoying to deal with on site if you start layering them in multiple directions like at a corner/junction. As a disclaimer I've never actually dealt with them before for this sort of purpose, so I'm not sure if it does or doesn't work in theory but I see little reason to find out aside from curiosity as I'd never detail it.

Clause 13.1.2.5 seems intended for a different scenario where for whatever reason you need 100% development at a certain location rather than starting with the 50% from a standard cog. With a curve diameter of 10db or greater, you can take your development length as though it were a straight bar.

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Why yes, I do in fact have no idea what I'm talking about

 

[Agent666]

That's some weird arse detailing if the code is saying you need a continuous radius like shown for walls in buildings of four or more storeys.

The detail in AS code for less than 4 storeys would be acceptable in NZ for any building as a comparison (one of several options we have for anchoring end region horizontal reinforcement). It's not clear to me what the 4 storey or greater detail is achieving that two 90 degree hooks in a ubar wouldn't. Additionally as Just Some Nerd notes, at intersections and corners it becomes really hard to do that and have any vertical reinforcement in the corners within the horizontal curved bar.

As long as you have a standard hook the assumption is your horizontal reinforcement is developed at the end of the wall, no specific calculation is really required in a similar manner as a beam stirrup anchoring around a bar. It's developed.

The around a curve stuff is I think more for say a situation where a bar going into the face of a wall where you cannot achieve a full development length for a 90 degree hook (say wall isn't thick enough to achieve this), if you limit the bend diameter you don't crush the concrete so much and code implies you can use an equivalent length to a straight development length continuing around the curve. British standards also allow this for development (in NZ its not allowed).

https://engineervsheep.com

 

[rscassar]

The boundary elements only says that bend radius to be considered in detailing. The lapped U-bars are still sufficient with the 5*db bend radius.

 

[rapt]

AS3600 says you do not get full development from a standard hook.

I think Eurocode has limits on it also.