From the Canadian code...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

The following picture clarify what is needed
Thanks.

5.4.2.4 Modulus of Elasticity
In the absence of measured data, the modulus of elasticity, Ec, for concretes with unit densities between
1440 and 2500 kg/m3 and specified compressive strengths up to 105 MPa may be taken as:

Ec= 0.043* K1*(γc**1.5 )* SQRT( fc')

K1 = correction factor for source of aggregate to be taken as 1.0 unless determined by physical test,
and as approved by the authority of jurisdiction

γc = unit density of concrete (kg/m3);

fc' = specified compressive strength of concrete (MPa)

I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

Thanks HTURKAK... I'll add this to my program. This is the 2010 edition, I assume. Is this for SI reference? why output in Ksi, and not MPa?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

If you want to use the AASHTO formulas, why not just convert the concrete properties to English units?

Btw, if you read the commentary, you'll see that for the range of strengths that it covered (up to 10ksi), the equation in the 2010 spec can still be used (other documentation indicates it's actually more accurate). They changed it in the later specs so it would cover concrete strengths up to 15ksi. For lower strength concrete, the new curve doesn't fit the empirical data as well as the old one did. IOW, they sacrificed accuracy in the lower-strength ranges to have one equation for concrete strengths up to 15ksi. All that to say, if you're calculating Ec for concrete with strength of 10 ksi or less, it would be easier and better to just use the equation from the 2010 spec (same as equation C5.4.2.4-2). I pretty much always use Eq. C5.4.2.4-3.

Quote (dik

... I'll add this to my program. This is the 2010 edition, I assume. Is this for SI reference? why output in Ksi, and not MPa?)

-This is from AASHTO LRFD Bridge Design Specifications SI Units

- The output unit of Ec for this formula is MPa.

The excerpt from the AASHTO SI Units:





For your example ; ( γc = 2300 (kg/m3), fc' = 25 (MPa)) The formula suggested at AASHTO SI units yields ;

Ec= 0.043* (2300**1.5 )* SQRT( 25)=23715 MPa

I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

Thanks... a bps...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik