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IRC 112 codes of practice for road bridges - Discussion

 
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Kooluthum Sukhesh
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PostPosted: Thu Feb 21, 2013 6:17 pm    Post subject: IRC 112 codes of practice for road bridges - Discussion Reply with quote

Dear Sefins,

The recent code of practice for design of concrete road bridge IRC 112 is based on Limit state design. The code gives rectangular stress distribution for design of flexural members. But as per IS-456 the stress block is parabolic. With the factors given in IRC- 112, the formula for limiting moment of resistance, moment of resistance of the section for the provided reinforcement etc. derives out to be same as that of what given in IS 456 for concrete mix below 60Mpa. But the shear design is different. Can we be able to use the interaction chart given in IS SP16 for design of biaxial columns and also procedure given for slender columns as per SP-16 for bridge piers also. I request engineers working in the area to participate in this discussions on various aspects of design guidelines as per IRC 112 especially on topics like design of prestressed concrete members, ultimate strength and limit state design for shear for PSC members , durability recommendations, and load combinations to be followed referring to IRC-6 2010 for ULS and SLS methods

With best regards

Sukhesh
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Dr. N. Subramanian
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PostPosted: Fri Feb 22, 2013 2:46 pm    Post subject: Re: IRC 112 codes of practice for road bridges - Discussion Reply with quote

Dear Er Sukhesh,

I thank you very much for sharing this info about IRC 112. Can you just post the page containing the stress block and the equation. I want IS 456 also to adopt rectangular stress block, since it will simplify the calculation. Most of the int. Codes such as ACI, British, Canadian, NZS codes have adopted the rectangular stress block only. Of course one can use the interaction curves in SP 16, even when they are using rect stress block. It was the brilliant idea by Whitney in the 1940s that has resulted in the simplified rect. Block, which produces results that is different from the actual stress block by 2to 4 % only!

Best wishes,
Subramanian
P.S. Only a few engineers and companies are involved in the design of bridges. My friend Er S. P. Srinivasan and Er Alok , who regularly contribute in SEFI are working in bridges. Hope they will reply to your comments.

Kooluthum Sukhesh wrote:
Dear Sefins,

The recent code of practice for design of concrete road bridge IRC 112 is based on Limit state design. The code gives rectangular stress distribution for design of flexural members. But as per IS-456 the stress block is parabolic. With the factors given in IRC- 112, the formula for limiting moment of resistance, moment of resistance of the section for the provided reinforcement etc. derives out to be same as that of what given in IS 456 for concrete mix below 60Mpa. But the shear design is different. Can we be able to use the interaction chart given in IS SP16 for design of biaxial columns and also procedure given for slender columns as per SP-16 for bridge piers also. I request engineers working in the area to participate in this discussions on various aspects of design guidelines as per IRC 112 especially on topics like design of prestressed concrete members, ultimate strength and limit state design for shear for PSC members , durability recommendations, and load combinations to be followed referring to IRC-6 2010 for ULS and SLS methods

With best regards

Sukhesh
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bsec
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PostPosted: Sun Feb 24, 2013 2:10 pm    Post subject: Re: IRC 112 codes of practice for road bridges - Discussion Reply with quote

Dear Mr Sukhesh,

IRC:112 gives 3 alternative stress-strain curve for concrete (i,e. Parabolic-rectangular, equivalent rectangular and Bi-Linear). This is in line with Euro Code - EC2. It is the designer's choice.

Your second querry - whether the curves of SP16 can be used for Bridges designed with IRC112 or not ....Answer is NO - Theoretically. This is because the strain diagrams at failure is different for reinforcement in IRC:112 as compared to IS 456.

However I have a feeling that the results will not be much different for Flexural Members, subjected to pure bending. For members subjected to axial load and bending, results are going to be different.

It may also be noted that as per IRC:112, the material safety factors (gamma 'm' and gamma 'c') are not constant and for accidental load combinations, these values also change. It would therefore be advisable that excel sheets be developed to take care of these aspects or alternatively use commerial softwares, which can take all these factors into account.

Best Wishes

Alok Bhowmick


Kooluthum Sukhesh wrote:
Dear Sefins,

The recent code of practice for design of concrete road bridge IRC 112 is based on Limit state design. The code gives rectangular stress distribution for design of flexural members. But as per IS-456 the stress block is parabolic. With the factors given in IRC- 112, the formula for limiting moment of resistance, moment of resistance of the section for the provided reinforcement etc. derives out to be same as that of what given in IS 456 for concrete mix below 60Mpa. But the shear design is different. Can we be able to use the interaction chart given in IS SP16 for design of biaxial columns and also procedure given for slender columns as per SP-16 for bridge piers also. I request engineers working in the area to participate in this discussions on various aspects of design guidelines as per IRC 112 especially on topics like design of prestressed concrete members, ultimate strength and limit state design for shear for PSC members , durability recommendations, and load combinations to be followed referring to IRC-6 2010 for ULS and SLS methods

With best regards

Sukhesh
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gautam chattopadhyay
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PostPosted: Fri Mar 01, 2013 9:10 am    Post subject: IRC 112 codes of practice for road bridges - Discussion Reply with quote

i feel we should develop new set of interaction curves as per stipulates of IRC 112 instead of following SP 16. Aloke is quite correct in saying that the curves of SP 16 are based on characteristic strengths of concrete stress block which is different from IRC 112. The formulations of SP 16 should be used with data from IRC 112 and new set of interaction diagrams should be developed.

However, in these days of widespread comuterisation I feel, we should prepare programs for P - M interaction and compute stresses in reinforcement and concrete instead of using curves anymore. Use of curves always suffers from human errors.

On Sun, Feb 24, 2013 at 7:40 PM, bsec <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Mr Sukhesh,

IRC:112 gives 3 alternative stress-strain curve for concrete (i,e. Parabolic-rectangular, equivalent rectangular and Bi-Linear). This is in line with Euro Code - EC2. It is the designer's choice.

Your second querry - whether the curves of SP16 can be used for Bridges designed with IRC112 or not ....Answer is NO - Theoretically. This is because the strain diagrams at failure is different for reinforcement in IRC:112 as compared to IS 456.

However I have a feeling that the results will not be much different for Flexural Members, subjected to pure bending. For members subjected to axial load and bending, results are going to be different.

It may also be noted that as per IRC:112, the material safety factors (gamma 'm' and gamma 'c') are not constant and for accidental load combinations, these values also change. It would therefore be advisable that excel sheets be developed to take care of these aspects or alternatively use commerial softwares, which can take all these factors into account.

Best Wishes

Alok Bhowmick


      Kooluthum Sukhesh wrote:                Dear Sefins,

The recent code of practice for design of concrete road bridge IRC 112 is based on Limit state design. The code gives rectangular stress distribution for design of flexural members. But as per IS-456 the stress block is parabolic. With the factors given in IRC- 112, the formula for limiting moment of resistance, moment of resistance of the section for the provided reinforcement etc. derives out to be same as that of what given in IS 456 for concrete mix below 60Mpa. But the shear design is different. Can we be able to use the interaction chart given in IS SP16 for design of biaxial columns and also procedure given for slender columns as per SP-16 for bridge piers also. I request engineers working in the area to participate in this discussions on various aspects of design guidelines as per IRC 112 especially on topics like design of prestressed concrete members, ultimate strength and limit state design for shear for PSC members , durability recommendations, and load combinations to be followed referring to IRC-6 2010 for ULS and SLS methods[/color:50cebb1344]

With best regards

Sukhesh     
     



     


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spsvasan
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PostPosted: Sat Mar 09, 2013 12:40 am    Post subject: Reply with quote

Dear Sefians

There seems to be a printing error in clause 10.3.3.2 of IRC 112 - 2011. The term "z" is defined as "0.9". It should be "0.9 x d".

Regards
S.P.Srinivasan
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abhishek_ecs
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PostPosted: Mon Nov 27, 2017 1:40 pm    Post subject: Reply with quote

I want to ask two questions.
Q1.If I design a bridge pier for biaxial bending as per sp16 interaction curves, will the resultant section and reinforcement lead to an over safe section or under safe section vis-a-vis IRC 112.If we consider a circular pier, I feel Sp 16 gives an over safe section, because as per IRC 112 cl 8.3.2, eq 8.3 value of alpha will be 2 while as per is 456 it will be one.Since MEDx/MRDx (or Mux/Mux1 as per is 456) is less than 1 ,with alpha value of 2,sections which will be unsafe as per IS 456 can become safe as per IRC 112.Please comment.
Q2.Can you recommend a good book on bridge pier design.

Thanks.



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abhishek_ecs
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PostPosted: Sat Dec 02, 2017 1:06 pm    Post subject: Re: IRC 112 codes of practice for road bridges - Discussion Reply with quote

Sir,how is the strain diagram at failure for reinfocement in irc 112 and is 456 is different? In fig 6.2 irc 2011 factored simplified deaign bilinear diagram is same as fig 23 of is 456.For basic and seismic combination, irc and is 456 values are similar.

bsec wrote:
Dear Mr Sukhesh,

IRC:112 gives 3 alternative stress-strain curve for concrete (i,e. Parabolic-rectangular, equivalent rectangular and Bi-Linear). This is in line with Euro Code - EC2. It is the designer's choice.

Your second querry - whether the curves of SP16 can be used for Bridges designed with IRC112 or not ....Answer is NO - Theoretically. This is because the strain diagrams at failure is different for reinforcement in IRC:112 as compared to IS 456.

However I have a feeling that the results will not be much different for Flexural Members, subjected to pure bending. For members subjected to axial load and bending, results are going to be different.

It may also be noted that as per IRC:112, the material safety factors (gamma 'm' and gamma 'c') are not constant and for accidental load combinations, these values also change. It would therefore be advisable that excel sheets be developed to take care of these aspects or alternatively use commerial softwares, which can take all these factors into account.

Best Wishes

Alok Bhowmick


Kooluthum Sukhesh wrote:
Dear Sefins,

The recent code of practice for design of concrete road bridge IRC 112 is based on Limit state design. The code gives rectangular stress distribution for design of flexural members. But as per IS-456 the stress block is parabolic. With the factors given in IRC- 112, the formula for limiting moment of resistance, moment of resistance of the section for the provided reinforcement etc. derives out to be same as that of what given in IS 456 for concrete mix below 60Mpa. But the shear design is different. Can we be able to use the interaction chart given in IS SP16 for design of biaxial columns and also procedure given for slender columns as per SP-16 for bridge piers also. I request engineers working in the area to participate in this discussions on various aspects of design guidelines as per IRC 112 especially on topics like design of prestressed concrete members, ultimate strength and limit state design for shear for PSC members , durability recommendations, and load combinations to be followed referring to IRC-6 2010 for ULS and SLS methods

With best regards

Sukhesh
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