In order to estimate the structural behavior of masonry close to reality by using RFEM, it is necessary to select a material and a material model first. Since masonry responds to tension by cracking, you have to select a nonlinear material model. This can be selected if the RF-MAT NL add-on module is available.
With RFEM 5.6.1103 and RSTAB 8.6.1103, there is an improved result output for the nonlinear calculation of reinforced concrete design in RF‑CONCRETE Members and CONCRETE. The new result windows include tables with a wide range of loading results; for example, governing load with the maximum ratio. In addition, you can now display the envelope results for the maximum ratio graphically.
One of my earlier articles described the Isotropic Nonlinear Elastic material model. However, many materials do not have purely symmetrical nonlinear material behavior. In this regard, the yield laws according to von Mises, Drucker-Prager and Mohr-Coulomb mentioned in this previous article are also limited to the yield surface in the principal stress space.
In practice, an engineer often faces the task of representing the support conditions as close to the reality as possible in order to be able to analyze the deformations and internal forces of the structure subjected to their influence and to enable construction that is as cost-effective as possible. RFEM and RSTAB provide numerous options for defining nonlinear nodal supports. The first section of my article describes the options for creating a nonlinear free support and provides a simple example. For a better understanding, the result is always compared to a linearly defined support.
Strain hardening is the material ability to reach a higher stiffness by redistributing (stretching) microcrystals in the crystal lattice of the structure. A distinction is made between the material isotropic hardening as scalar quantities or tensorial kinematic hardening.
When designing reinforced concrete components according to EN 1992‑1‑1 [1], nonlinear methods of determining internal forces for the ultimate and serviceability limit states are possible. In this case, the internal forces and deformations are determined with respect to their nonlinear behaviour. The analysis of stresses and strains in cracked state usually provides the deflections, which clearly exceed the linearly determined values.
RFEM and RSTAB provide numerous options for nonlinear definitions of nodal supports. With regard to an earlier article, further possibilities of the nonlinear support design for a movable support are shown in a simple example in this article. For a better understanding, the result is always compared to a linearly defined support.
For structural dimensioning according to the valid rules, there are often several options or calculation methods to determine the internal forces. It is up to the engineer to decide which theory is suitable for designing the structure.
Shell buckling is considered to be the most recent and least explored stability issue of structural engineering. This is due less to a lack of research activities than to the complexity of the theory. With the introduction and further development of the finite element method in structural engineering practice, some engineers no longer have to deal with the complicated theory of shell buckling. Evidence of the problems and errors to which this gives rise is very well summarized in [1].
Orthotropic material laws are used wherever materials are arranged according to their loading. Examples include fiber-reinforced plastics, trapezoidal sheets, reinforced concrete, and timber.