RF-CONCRETE NL Add-on Module for RFEM

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Physical and Geometrical Nonlinear Calculation of Reinforced Concrete Beam and Plate Structures

The RF-CONCRETE NL add‑on module is an extension of the RF‑CONCRETE module group and consists of two parts, just as the main module:

  • RF‑CONCRETE NL as an extension of RF‑CONCRETE Surfaces allows for realistic analysis of deformations, stresses and crack widths of members, plates, walls, planar structures and shells made of reinforced concrete by considering the nonlinear behavior of composite material when determining internal forces and deformations.
  • RF‑CONCRETE NL as an extension of RF‑CONCRETE Members allows for nonlinear analysis of 2D and 3D beam structures in the ultimate and serviceability limit states. For example, it is possible to perform a nonlinear calculation of compression elements prone to instability risks, or to calculate deformations of frame constructions consisting of reinforced concrete beams close to reality.
The following standards are available for nonlinear calculation:

With RF‑CONCRETE NL, you can quickly and easily perform the design for limiting the deformation of reinforced concrete members and surfaces in the cracked state (state II).

  1. Settings for non-linear calculation


    • Iterative nonlinear calculation of deformations for beam and plate structures consisting of reinforced concrete by determining the respective element stiffness subjected to the defined loads
    • Deformation analyses of cracked reinforced concrete surfaces (state II)
    • General nonlinear stability analysis of compression members made of reinforced concrete, for example according to EN 1992-1-1, Cl. 5.8.6
    • Tension stiffening of concrete applied between cracks
    • Numerous National Annexes available for the design according to Eurocode 2 (EN 1992-1-1:2004 + A1:2014, see EC2 for RFEM)
    • Optional consideration of long-term influences such as creep or shrinkage
    • Nonlinear calculation of stresses in reinforcing steel and concrete
    • Nonlinear calculation of crack widths
    • Flexibility due to detailed setting options for calculation basis and extent
    • Graphical results output integrated in RFEM, for example deformation or sag of flat slab
    • Numerical results clearly arranged in tables and graphical display of the results in the model
    • Complete integration of results in RFEM printout report
  2. Material properties for nonlinear calculation


    RF-CONCRETE Surfaces:

    The nonlinear calculation is activated by selecting the design method of the serviceability limit state. You can individually select the analyses to be performed as well as the stress-strain diagrams for concrete and reinforcing steel. It is possible to influence the iteration process by the control parameters of the convergence accuracy, the maximum number of iterations, the arrangement of layers in relation to the cross-section depth, or the damping factor.

    You can set the limit values in the serviceability limit state individually for each surface or a surface group. Allowable limit values are defined by the maximum deformation, the maximum stresses, or the maximum crack widths. The definition of the maximum deformation requires an additional specification whether the non-deformed or the deformed system should be used for the design.

    RF-CONCRETE Members:

    The nonlinear calculation can be applied to the ultimate and the serviceability limit state design. In addition, you can specify the concrete tensile strength or the tension stiffening between the cracks. It is possible to influence the iteration process by the control parameters of the convergence accuracy, the maximum number of iterations, and the damping factor.

  3. Non-linear calculation


    RF-CONCRETE Surfaces:

    The nonlinear deformation analysis is performed by an iterative process considering the stiffness in cracked and non-cracked sections. The nonlinear reinforced concrete modeling requires definition of material properties varying across the surface thickness. Therefore, a finite element is divided into a certain number of steel and concrete layers in order to determine the cross-section depth.

    The mean steel strengths used in the calculation are based on the "Probabilistic Model Code" published by the JCSS technical committee. It is up to you if the steel strength is increased until the ultimate tensile strength is reached (increasing graph in the plastic range). Regarding material properties, it is possible to control the stress-strain diagram of the compressive and tensile strength. For the concrete compressive strength, you can select a parabolic or a parabolic-rectangular stress-strain diagram. On the tension side of the concrete, it is possible to deactivate the tensile strength as well as to apply a linear-elastic diagram, a diagram according to the CEB-FIB model code 90:1993, and concrete residual tensile strength considering the tension stiffening between the cracks.

    Furthermore, you can specify which result values should be displayed after the nonlinear calculation at the serviceability limit state:

    • Deformations (global, local based on non-/deformed system)
    • Crack widths, depths, and spacing of the top and bottom side in principal directions I and II
    • Stresses of the concrete (stress and strain in principal direction I and II) and of the reinforcement (strain, surface, cross-section, cover, and direction in each reinforcement direction)
    RF-CONCRETE Members:
    The nonlinear deformation analysis of beam structures is performed by an iterative process considering the stiffness in cracked and non-cracked sections. The material properties of concrete and reinforcing steel used in the nonlinear calculation are selected according to a limit state. It is possible to apply the composite action of concrete tensile strength between the cracks (tension stiffening) using a modified stress-strain diagram of reinforcement steel, or the concrete residual tensile strength.
  4. Graphical results represented in RFEM with deformation in state II


    After the calculation, the module shows clearly arranged tables listing the results of the nonlinear calculation including all intermediate values. Graphical representation of design ratios, deformations, concrete and reinforcing steel stresses, crack widths, crack depths, and crack spacing in RFEM facilitates a quick overview of critical or cracked areas.

    Error messages or remarks concerning the calculation help you find design problems. Since the design results are displayed by surface or by point including all intermediate results, you can retrace all details of the calculation.

    Due to the optional export of input or result tables to MS Excel or OpenOffice.org Calc, the data remains available for further use in other programs. The complete integration of results in the RFEM printout report guarantees verifiable structural design.

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