Concrete Elasticity and tensile strength
Concrete Elasticity and tensile strength
(OP)
Hi, I have the following expressions to asses Concrete Elasticity and tensile strength. My problem is that they are much different between them. Which criteria would recommend me? Thanks
1-
Ec: 15000*(f'c)^0,5 [kgf/cm2]
fr: 2*(f'c)^0,5 [kgf/cm2]
---------------------------------
2-
Ec: 47000*(f'c)^0,5 [kgf/cm2]
fr: 6.3*(f'c)^0,5 [kgf/cm2]
---------------------------------
3-
Ec: 8000*(f'c^2+8)^(1/3) [kgf/cm2]
fr: 0.3*(f'c^2)^(1/3) [kgf/cm2]
1-
Ec: 15000*(f'c)^0,5 [kgf/cm2]
fr: 2*(f'c)^0,5 [kgf/cm2]
---------------------------------
2-
Ec: 47000*(f'c)^0,5 [kgf/cm2]
fr: 6.3*(f'c)^0,5 [kgf/cm2]
---------------------------------
3-
Ec: 8000*(f'c^2+8)^(1/3) [kgf/cm2]
fr: 0.3*(f'c^2)^(1/3) [kgf/cm2]






RE: Concrete Elasticity and tensile strength
RE: Concrete Elasticity and tensile strength
RE: Concrete Elasticity and tensile strength
RE: Concrete Elasticity and tensile strength
All the widely used international codes have equations for these values, and they give similar results, but you have to use the specified units.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Concrete Elasticity and tensile strength
The second are what we use here, the are usually written in MPa
Ec=4700*(f'c)^0.5[MPa] is intended for secant young's modulus at 0,5*f'c
fct= 0.63*(f'c)^0,5 [MPa] refers for non direct stresses.
The third are ones i found between my university notes.
If I took the first and second pairs of expressions only. i'll still get a big differences with n=Es/Ec, critical rotation, critical bending, neutral axis position, yielding beginning.
I'm only trying to get an approximation of deflections under earthquake I've been checking for effective EcIg considerations for RC, cracks influence and that's ok, but my initial values and stress-and-strain curve rely on this parameters and i think that 47000/15000~=3,1 is a big difference to start the analysis.
RE: Concrete Elasticity and tensile strength
That's not actually right. The first one appears to be about right with kgf/cm2 units.
The second one is the ACI metric equation, which should have a factor of 4700 with MPa units.
The units of the factors are (stress)^0.5, which explains why the results you are getting differ by a factor of about 3, since you have factored by 10, rather than 10^0.5.
If you want to compare the results, use the units they were written for, then convert the results to common units.
Both 1 and 2 give an E value of about 27 GPa.
I don't know what the intended units of the third one are.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Concrete Elasticity and tensile strength
RE: Concrete Elasticity and tensile strength
Thinking about the expression 4.700*sqrt(fc[MPa]) it's not just about making 4.700*sqrt(fc*10[kgf/cm2]),
this retrieves [MPa], so there should be a hidden sqrt(MPa) to achieve the result in proper units.
I mean 4.700*sqrt(fc[MPa])*sqrt([MPa]), so to change it i'll need:
4.700*sqrt(fc*10[kgf/cm2))*sqrt(10[kgf/cm2]), getting about 15.000*sqrt(fc), with fc expressed in Kgf/cm2 and also the result