Concrete Behavior
This elastic modulus of concrete is defined by the user in the materials window. You can choose to use the code equation in table 3.1 or a specified value.
When you directly specify values, there must be two elastic modulus values:
- Eci = value for initial service (transfer) cross section analyses
- Ec = value for all other conditions
When the EC2 code equation is selected the following values are used:
where
| Eci = 22,000[(fcki + 8)/10]0.3 MPa |
| Ec = 22,000[(fck + 8)/10]0.3 MPa |
| = | ||
| = |
For calculations based on the "concrete section", concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits.
For detailed cross section analyses three different stress strain curves are used. All three stress-strain curves are parabolic-linear curves as detailed in clause 3.1.7. The transition strain is at εc2.
- For initial stress conditions, the peak stress in the stress strain curve is
0.85fck / (SLS)γc
(γc = 1.0 for UK National Annex) - For service stress conditions, the peak stress in the stress-strain curve is
0.85fck / (SLS)γc
(γc = 1.0 for UK National Annex) - For strength conditions, the peak stress in the stress-strain curve is
0.85fck / (ULS)γc
(γc = 1.5 for UK National Annex)
The strength stress-strain curves are truncated at a strain of εcu2. The other stress-strain curves have no limit strain.
Note: Calculations on the gross cross-section always use the Ec values calculated above, while the cracked cross-section strain analyses use the stress strain curve of Figure 3.3. The elastic modulus for these two conditions will therefore be different for most concrete strengths. This may have an effect on initial concrete strains and ECR calculations.