Material Behavior
Range I
In the range up to about σct ≤ 0.7·fctm, the concrete shows almost linear elastic behavior. The stiffness can be described easily by the tangent modulus Ec0m, derived for concrete subjected to compression.
Range II
If the load is further increased, the micro cracks already present in the unloaded concrete grow until they finally reach tensile strength fctm.
Furthermore, the stiffening effect of the concrete in the tension zone (tension stiffening) can be applied. The background to this is described in Chapter Tension Stiffening.