29 November 2019

FAQ 004252 EN

Gerhard Rehm



In a model with surface supports, the calculation does not converge or the result has very large deformations and implausible stresses. What are the reasons for this?


The definition of surface supports should be as realistic as possible. Experience shows that the equation solver works most effectively with this. To simplify matters, degrees of freedom are often defined as 'fixed'. However, this can have a big impact on the overall stiffness matrix and cause numerical problems (see Figure 01).

It is better to work with springs in order to avoid the numerical problems. It is often sufficient to define very stiff springs (see Figure 02). The same applies to the foundation perpendicular to the surface. You can find more information in [1] and in the links below this FAQ.


Surface support Convergence


[1]   Christian Barth und Walter Rustler. Finite Elemente in der Baustatik-Praxis. Bauwerk, Berlin, 2010.


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