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Beam reinforcement details

 
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ramu_se
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Joined: 30 Oct 2017
Posts: 75

PostPosted: Tue Aug 09, 2022 4:59 am    Post subject: Beam reinforcement details Reply with quote

Dear All,

The area of steel required in the tension zone is 1000 mm2, and the size of the beam is 225 x 450 mm continuous beam.

Reinforcement required is 3 T16 main bar and 2T16 extra bar which is required in one particular span of the continuous beam.

How to arrange the main bar and extra bar?

If provide 3 T16 throughout the beam which is uneconomical since it is needed in one particular span of the continuous beam.

The remaining spans of the continuous beam hold good with 2T16.

Can we provide 3T16 only in that particular span, and curtail the bar?
or can we provide the main bar as 2T16 and an extra bar as 3T16?

Attached is the image for your reference. The clouded area is the tension zone which required steel 3 T16 + 2 T 16.

Kindly provide your guidance.

Thanks & Regards,
Ramu.



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vikram.jeet
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Joined: 26 Jan 2003
Posts: 3559

PostPosted: Tue Aug 09, 2022 7:26 am    Post subject: Reply with quote

For detailing please see structural drawings attached at the end of SP34. These drawings may teach you better detailing skills.

In yr case it seems bottom reinf is 10 cm2 for mid span of end span , you can provide 3 nos 16 dia continued in all spans at bottom , and provide balance requirement I.e 2 nos 16 in end span at bottom in second layer , but these bars can be curtailed at about 0.10 L from support face on either side. For other inner spans requirements would be less and extra bars in second layer could be 2-12 dia or even 2-10 dia.at bottom face.

For top bars , better to have 2 -16  dia all through with extra bars at support s, but if u want to economise , you can provide 2-12 dia all thru and extra bars at supports  ( if need be there support bars can be added in second layer ) .

As I always say :
ANALYSIS is UNIVERSAL
DESIGN IS NATIONAL
DETAILING IS PERSONAL

AND
MODELLING HAS TO BE IDEAL ( In this age of softwares)
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spsvasan
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Joined: 18 Dec 2008
Posts: 364

PostPosted: Sun Aug 14, 2022 10:27 am    Post subject: Reply with quote

[quote="vikram.jeet"]For detailing please see structural drawings attached at the end of SP34. These drawings may teach you better detailing skills.

Dear Er.Ramu

I fully agree with Er.Vikramjeet.

it is essential to study SP34 to develop proper detailing skills.

But in the case of continuous beam with wildly differing adjacent spans, even SP34 leaves a lot to be desired. In your case, at grid F, the adjoining spans are 6'9" and 14'10". In such cases, it is better to get the bending moment diagram and calculate curtailment points for top reinforcement in accordance with clause 26.2.3 of IS 456.

In some extreme cases, the shorter span may be completely in hogging

S.P.Srinivasan
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vikram.jeet
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PostPosted: Mon Aug 15, 2022 3:30 pm    Post subject: Reply with quote

[quote="spsvasan"]
vikram.jeet wrote:
For detailing please see structural drawings attached at the end of SP34. These drawings may teach you better detailing skills.

Dear Er.Ramu

I fully agree with Er.Vikramjeet.

it is essential to study SP34 to develop proper detailing skills.

But in the case of continuous beam with wildly differing adjacent spans, even SP34 leaves a lot to be desired. In your case, at grid F, the adjoining spans are 6'9" and 14'10". In such cases, it is better to get the bending moment diagram and calculate curtailment points for top reinforcement in accordance with clause 26.2.3 of IS 456.

In some extreme cases, the shorter span may be completely in hogging

S.P.Srinivasan


Yes , it is very sane advice from Er SPS.
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