Development Lenghts
Development Lenghts
(OP)
Sirs,
Good Morning!
Regarding development lengths, is it okay to ignore ldh for hooked bars but still hook it and let it equal to Ld for straight bars?
For more details please see attachment
Thank You in advance
Good Morning!
Regarding development lengths, is it okay to ignore ldh for hooked bars but still hook it and let it equal to Ld for straight bars?
For more details please see attachment
Thank You in advance






RE: Development Lenghts
It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
If it requires an Ld to develop a straight bar, then if you have the same length of straight bar and put a bend in it, one would think it would be at least as strong.
The only reason that I can think of is that the bar is 'pulling away' from the concrete at the outside of the radius... but, then it's pushing against the inside of the radius.
Can anyone explain why it would not be as strong?
Dik
RE: Development Lenghts
RE: Development Lenghts
http://www.dspace.rice.edu/bitstream/handle/1911/1...
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
Dik
RE: Development Lenghts
Take the extreme case in the detail. If you ignore ldh entirely you have the potential for the hook to be turned down immediately after the bar passes the face of the support. That can't work and would result in minimum coverage and the hook pulling through the face of the support and possibly from the face of the beam before reaching full capacity. This would also happen with thin walls and columns where ldh could not be observed.
I could see the detail working in some scenarios. Perhaps where there was supplemental reinforcement under the hook or where a reasonable ldh was "unofficially" observed.
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
RE: Development Lenghts
Dik
RE: Development Lenghts
I assume that question was for me.
BS8110 has a formula for bearing stress in the curve which is dependant on the radius and the force in the bar in clause 3.12.8.25.2. You can rearrange the formula to give a minimum radius for the amount of development of the bar required.
AS3600 says that the bar can be considered to develop stress around a curve (ignore cog benefit and treat it as a normal length of bar) if the radius of the bend is greater than 10 times the bar diameter. But really this should be related to concrete strength etc as BS8110 does.
RE: Development Lenghts
On the list for the next revision?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Development Lenghts
My understanding is that the question i raised is OK as per ACI code.
Please correct me if I am wrong..
RE: Development Lenghts
Dik
RE: Development Lenghts
Dik
RE: Development Lenghts
Sorry, I am away on holidays and no longer have access to a copy. The local engineering library should ahve a copy!
If you search on Bing for BS8110 + 3.12.8.25.2, it comes up!
RE: Development Lenghts
IMO I don't think the supplemental reinforcement can be said to reduce the ldh for a "standard hook" since ldh is a defined constant. But if you are using some modified configuration that includes supplemental reinforcement then I certainly agree than a "standard hook" should not always be necessary in order to obtain a reduced "lead in" as it was called.
We do this sort of thing all the time in anchor bolt design when Appendix D is not suitable for anchorage in small piers. The codes/standards should not prevent an engineer from using alternate rational methods such as strut and tie, etc.