RF-CONCRETE Surfaces Version 5

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RF-CONCRETE Surfaces Version 5

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2.7.4 Cross-Section Properties

Cross-Section Properties

The cross-section properties are determined for both reinforcement directions Φ and both cross-section states c (cracked/uncracked). For state I (uncracked cross-section), a linear-elastic behavior of the concrete on the tension side is applied. For state II (cracked cross-section), the tensile strength of concrete is not applied.

If no axial forces nΦ act (e.g. in the type of model 2D - XY (uZ / φX / φY), this part of the calculation is independent of internal forces, and a direct calculation of the cross-section properties is possible. In the other cases, the compression zone depth is calculated by means of an iterative method of calculation, the so-called "binary method". For numerical reasons, the program uses the minimum value for the reinforcement ratio ρmin = 10- 4 in every iteration step, meaning if there is no reinforcement, a virtual minimum reinforcement area is applied. Such a small value has no appreciable influence on the results (stiffnesses).

The calculated ideal cross-section properties (related to the concrete cross-section) in a reinforcement direction φ and the crack state c are the

  • moment of inertia to the ideal center of gravity IΦ,c,
  • moment of inertia to the geometric center of the cross-section I0.Φ,c,
  • cross-section area AΦ,c,
  • eccentricity of the ideal center of gravity eΦ,c.

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