dia 10mm longitudinal bar

[7thSky]

Can we use dia 10mm bar in the beam as a top and bottom reinforcement as per British Standard.My problem is I can only use either dia 10mm or dia 20mm for longitudinal reinforcement for continuous beam due to availability of reinforcement on site.Code is specific for column not to be used dia 10 but I am not sure about beam.please help

 

[normm]

7thSky

In my experience, you can use 10 mm dia longitudinal bars, as long as you meet the minimum percentage requirement -- 0.13 percent.

 

[7thSky]

Normm
Thank you very much I have used dia 10mm as a top bar and hoping should be ok.
Thanks

 

[hokie66]

It's not a matter of hoping. You have to have enough reinforcement to take the tension due to bending. You have given no information about the beam, so we can't be very helpful.

 

[msquared48]

10mm is comparable to a #3 bar, and that seems awful light for a concrete beam, depending on the beam size and loading.

As Hokie suggested, more info would be helpful.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[7thSky]

my beam size is 300mm(12in) wide by 500mm(20in) deep.I have used 4 No. dia 10mm at and 4 No dia 20mm at the bottom for simply supported beam.I have added two extra dia 20(Top) at support in case of continuous beam.These bar is enough for bending and also it covers the minimum reinforcement 0.13%bh .Guys what do u say now.Is that seems ok ?

 

[hokie66]

I don't know where 0.13% steel comes from. That sounds like minimum shrinkage reinforcement, and minimum flexural reinforcement would be more in the range of 0.3%, but I am not up to date with British Standards. 0.13% would probably be less capacity than the cracking moment...especially bad for a simple span.

 

[normm]

0.13 percent is the minimum requirement for shrinkage requirements.

Of course you need to provide the amount of reinforcement required from bending considerations. I thought the question was once you know the amount of reinforcement you need, does it matter what dia bars are used to provide the area of reinforcement -- can it be as low as 10 mm?

My view is you can use as low as 10 mm. But you need to calculate the total amount you need and satisfy that. What that total amount is is a seperate question

 

[BAretired]

It would be much better if you could add 15M bars to your available stock. 10M bars are a bit too light for beam reinforcement.

BA

 

[hokie66]

7thSky,
You are obviously in a position where adequate support is not available. Perhaps if you can give us your actual problem in the form of loads on the beam or the beam moments, we could give better advice. Minimum steel percentage is only part of the solution.

 

[rapt]

Hokie66,

BS8110 uses .13% as miimum reinforcement for rectangular sections. Unfortunately, it is not related to concrete strength as it should be. .13% is correct for about 20MPa concrete. For "real" concrete strengths used these days, it should be significantly higher.

But nothing seems to fall down in UK because of it!

 

[7thSky]

For simply supported beam I have used 4 dia 10mm bar as a hanger bar at the top for a beam of 500 deep and 400mm wide.I havent seen any restriction using dia 10m bar in British code.

 

[dik]

Hokie... it's minimum flexural rfg depending on yield... Beams can be designed for min rfg (not TS) or designed for min moment increased by 33%.

Dik

 

[ahmedhegazi]

Yes you can use T10 bars for beams as tension Reinforcement and top mid span bars ,
IMO , would not recommend it as main bars ,but if you have to, then do it and do not worry.

 

[7thSky]

ok guys thanks all of you
cheers