Mixing rebar sizes
Mixing rebar sizes
(OP)
If I can design a concrete beam and the area of steel I need is best suited by mixing two different sizes of rebar (let's say #10 & #11), which would be recommended to be set on the outer sides and which in the inner part of the beam?






RE: Mixing rebar sizes
RE: Mixing rebar sizes
RE: Mixing rebar sizes
Also, consider two different sized bars (say #10 and #11) mixed together for the same purpose. Under load, both will stretch the same amount in the beam, but the stress will not be proportionally divided between the two sizes in the intended manner. The #11 will be more heavily loaded than expected. Edit: My statement in this paragraph is wrong, sorry. SRE
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Mixing rebar sizes
That I was not aware of by anything official or published. Would you be kind enough to give me any references to that? I am very interested in this. I have to confess that I suspected that the size difference could make either the smaller or the larger behave differently than expected. Any literature/reference on this matter will be very appreciated.
I was expecting actually an answer in case I do proceed with the two different sizes and I had thoughts such as:
A) Put the smaller sizes outside because smaller will better integrate with the concrete and will have less chance of cracking when close to two surfaces instead of one surface.
B) Put the larger bars outside because in case of torsion they will perform better than the smaller rebars
And irrelevant to the above mentioned, ... 'Don't mix them because someone will place them in the wrong order" which I did receive.
RE: Mixing rebar sizes
I think SlideRuleEra meant to say... The two bars will stretch the same, strain the same, so the stress in the two bars should be essentially the same. But, the forces in the two bars will be different in proportion to their areas. The primary thought trying to be conveyed is that to save a few bucks on steel, you should not do something (mixing bar sizes) which increases the potential of an error (rebar placement error) in the field. On the other hand, if the two bar sizes are significantly different in length or bending details, there is some less chance of confusing the two sizes during placement.
RE: Mixing rebar sizes
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: Mixing rebar sizes
dhengr - Thank you for "bailing me out".
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Mixing rebar sizes
RE: Mixing rebar sizes
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Mixing rebar sizes
RE: Mixing rebar sizes
As for placement of the larger bar, I agree with Jed that it will normally make sense to have additional bars shorter, in the area of maximum moment, and obviously the full length bars should go in the corner, but there will be times when it makes sense to use the smaller bar for full length, and the larger diameter for the additional shorter bars.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Mixing rebar sizes