RAM Concept performs cracked section analyses by iteratively solving for a cross section strain (top strain and bottom strain) that results in the cross section bending moment and axial force being equal to the applied moment and axial force.

In the cracked section analyses, RAM Concept considers concrete to have no tension strength. Since concrete obviously does have some tension strength, RAM Concept ’s assumption is equivalent to considering that the concrete has been previously cracked by some other loading condition. RAM Concept ’s assumption is conservative. This pre-cracked assumption is used to determine the cracked cross section stresses and the cracked moment of inertia. This assumption does not effect the ECR calculations as Branson’s formula does not consider the cracked moment of inertia unless the cross section stresses exceed the modulus of rupture.

When a cross section with no concrete tension strains is analyzed with a cracked section analysis, RAM Concept ’s analysis methods result in a transformed section analysis.

The parameters considered in a Rule Set’s cracked section analysis are

• For ECR (Effective Curvature Ratio) Calcs Only - The creep coefficient as specified in the Load History / ECR tab of the Calc Options dialog. This coefficient is the value of (total strain under constant stress) / (initial strain under same stress); a typical value is 3.35 (1.0 for initial strain and 2.35 for creep strain)
• For ECR Calcs Only - The shrinkage strain as specified in the Calc Options dialog.
• The standard instantaneous concrete stress-strain curve as defined above.
• All mild steel reinforcement (from all rule sets) in each cross section – this is the value reported by the Design Status area of steel plots, which will often be somewhat less than the value of the detailed reinforcement (number of bars and lengths).
• The displacement of concrete by reinforcement is not considered.
• The tendon stress strain curve for the type of rule set (see "Tendons – External Load or Internal Force?"). Cracked section analysis is not available for rule sets – such as Minimum Design – that do not inherently have a tendon stress-strain curve type associated with them.