Provide an SI equation for Modulus of Elasticity of Concrete in Accordance to AASHTO LRFD Bridge Design Specification of 9th edition
I have attached US unit.
Thank you.
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.
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.
