Concrete Behavior
You define the concrete elastic modulus in the materials window. You can choose to use code equation 8.5.1 with the inclusion of wc or a specified value.
- Eci = value for initial service (transfer) cross section analyses
- Ec = value for all other conditions
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For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits.
See Concrete Stress-Strain Curves for a description of the stress-strain curves used in a detailed cross section analysis.
The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.
Where applicable, the lightweight concrete modification factor is calculated using the values in 8.6.1 as follows:
- Lightweight concrete (assumed density of 105 pcf): 0.75
- Sand lightweight concrete( assumed density of 115 pcf): 0.85
- Normalweight concrete (assumed density of 145 pcf): 1.0
Linear interpolation is used between these values, which is also explicitly permitted by 8.6.1. The maximum density for the cross section is used in the calculation.