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Concrete:Seismic Design-Basic Questions

 
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kajal.chopra
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Joined: 26 Jan 2003
Posts: 102

PostPosted: Mon Nov 06, 2006 2:00 pm    Post subject: Concrete:Seismic Design-Basic Questions Reply with quote

I have some basic questions:

1.) As the concrete grade increases, the peak/crushing strain
decreses?Hence concrete of higher grade has less ductility as it
behaves in a more brittle mode due to less value of peak strain.

Then, why don't the codes specify a maximum limit on concrete grade for seismic resistant design?

2.)Modulus of Elasticity of concrete as per IS Code is given as
5000*squareroot(cube strength of concrete)

But , with reinforcement in it concrete would become more stiff.IS
there any prescribe approximate value for reinforced concrete in any
country code?

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rajmane
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Joined: 26 Jan 2003
Posts: 160
Location: Chennai

PostPosted: Thu Nov 09, 2006 8:13 am    Post subject: Concrete:Seismic Design-Basic Questions Reply with quote

9-11-2006

Dear all

1.) It is generally correct to say that as the concrete grade increases, the peak/crushing strain decreases. However, we should look at ductile behaiour of actual reinforced concrete member and this would depend on detailing also. It may not be adequate to look at concrete in isolation and therefore, it may not be necessary for the codes to specify a maximum limit on concrete grade for seismic resistant design.

2.) The value of Modulus of Elasticity of concrete given in IS Code  [ 5000 * squareroot (cube strength of concrete)],is for design purpose. The behaiour of actual reinforced concrete member would have the effect of confinement provided by the reinforcement, especially the stirrups, etc. The confinement effect would be often beneficial.

N P Rajamane
Deputy Director and Head, Concrete Composites Lab,
Structural Engg Research Centre, CSIR, Taramani, Chennai 600113
(Ph : 22549152 (D), 22549150 (CCLab), Res: 224417882)
Email : rajmane[AT]ser..., rajamanenp[AT]yah...

PS : The above opinion is personal and it may not be necessarily the view of SERC.

Struct

kajal.chopra[AT]red... wrote:

Quote:
I have some basic questions:

1.) As the concrete grade increases, the peak/crushing strain
decreses?Hence concrete of higher grade has less ductility as it
behaves in a more brittle mode due to less value of peak strain.

Then, why don't the codes specify a maximum limit on concrete grade for seismic resistant design?

2.)Modulus of Elasticity of concrete as per IS Code is given as
5000*squareroot(cube strength of concrete)

But , with reinforcement in it concrete would become more stiff.IS
there any prescribe approximate value for reinforced concrete in any
country code?


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