Without further definition, the member elements react linearly elastically in and about all assigned degrees of freedom in such analysis. Basically, this behaviour is defined by Hooke's law, which states that the deformation u of a solid is proportional to the acting load F, or its strain Δl depends linerly on the acting force F.
In reality, not every element reacts linearly elastically. For example, a slender circular member, with regard to its cross-section resistance, absorbs more tension than compression. This property based on force can be conceived and simulated by means of member nonlinearity in the numerical calculation. In this case, the member strain depends on the acting force nonlinearly due to the premature stability failure (buckling) in the compression state.
Member nonlinearities exist in various forms. Usually, they do not depend on the forces relating linearly to each other, but on the final effect on the elements in the calculation.
Typical Member Nonlinearities
- Failure under tension
- Yielding when plastic resistance is reached
- Rigid from the defined deformation u
Entering in RFEM and RSTAB
In RFEM and RSTAB, member nonlinearities can be entered and defined graphically via 'Insert' → 'Model Data' → 'Member Nonlinearities' → 'Dialog Box', or manually by using the Data Navigator or the corresponding tables.
The RF-/STEEL EC3 add-on module automatically transfers the buckling line to be used for the flexural buckling analysis for a cross-section from the cross-section properties. In particular for general cross -sections, but also for special cases, the assignment of the buckling line can be adjusted manually in the module input.
SHAPE-THIN Table "6.2 Classification of the Cross-Section According to EN 1993-1" and Stress Diagram
The material model Orthotropic Masonry 2D is an elastoplastic model that additionally allows softening of the material, which can be different in the local x- and y-direction of a surface. The material model is suitable for (unreinforced) masonry walls with in-plane loads.
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Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions