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Hi Kajal,

The research is going on but it is still not clear at what value of strength
the material becomes classically brittle & the slope of the descending
branch of the stress - strain curve becomes vertical and therefore not
practically usable in design.
In design, it is desirable that the concrete not crush or substantially
enter the descending branch of the curve before the steel has reached its
yield point.
Above is the reason why codes do not specify a maximum limit on concrete
grade for seismic resistant design.

Regards,

Siddharth Subhedar

-----Original Message-----
Message From kajal.chopra[AT]red... [mailto:kajal.chopra[AT]red...]
Sent: Tuesday, November 07, 2006 1:01 AM
To: SUBHEDAR Siddharth
Subject: Concrete:Seismic Design-Basic Questions

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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