 Analysis button
Material constitutive law for analysis
Prestressed Steel
CivilFEM has the option of choosing the analysis type in order to define the material behavior that the program will use during the solving process. Steel analysis types may be both linear and bilinear.
Linear
The linear elastic model is the most commonly used model to represent typical engineering materials. This model, that showcases a linear relationship between stresses and strains, is represented by Hooke’s Law. The figure below shows that stresses are proportional to strains in a uniaxial tension test. The ratio of stress to strain is the familiar definition of modulus of elasticity (Young’s modulus) of the material.
E (modulus of elasticity) = (axial stress)/(axial strain)
Linear analysis has the characteristic of not limiting the strain while stresses increase.
We could say that a linear diagram does not follow the real material behavior. However, this diagram is very useful if the user wants to perform an analysis in the linear stages of the material and doesn't need a more detailed but slower non-linear calculation.
If the user does not choose a particular analysis type, CivilFEM will apply a linear analysis by default.
Bilinear
Bilinear analysis is a non-linear analysis type, that behaves according to the following diagram.
A non-linear analysis can be applied in such cases as:
When a geometric non-linearity exists.
When a material non-linearity exists.
When a boundary condition non-linearity takes place, such as in cases having contacts, heat transmission...
The non-linear behavior described in the graphic shows that when a steel material has already reached the strain-stress limit, this value can't be surpassed.
That is, if material passes this strain-stress boundary, a plastic fracture will take place.
On the other hand, if bilinear analysis is active for a steel material, reinforced steel or prestressed steel, the properties bar shows the added "Hardening type" option. This utility will apply a different work hardening rule depending on the established option.
The hardening contains three different options: isotropic, kinematics and combined. Further information is detailed in the "work hardening rules" section.
| 
