Today I wrote the first time a contribution to a plug-in. The issue is more complex, so I will divide into several parts. The first part deals with some theoretical basis.
Most modules in RSTAB or RFEM're proof modules. The normal operation is that the internal forces with RSTAB or RFEM be identified and passed the qualifications of the components according to relevant standards with modules.
something different is the module RF-STABLE. This is not a normative Detection performed. Why do you need the module then?
At the beginning of structural analysis one is trying to decide whether the forces may be determined under the first-order theory, or whether the deformations have a significant influence on the forces, so the calculation is necessary for second-order theory.
What exactly "first-order theory" and "second-order theory" is, I will take in a later figure does something more closely. Here are just a very brief explanation. In the first-order theory assumes that the stress and strain are linearly related. If, for example, doubled in a single-span beam exposure, then doubled and the deflection. The balance of power can be placed on the undeformed system. Anders II on the theory of procedure. Here, no longer a linear relationship between stress and strain can be assumed. be the equilibrium of forces on the deformed system set up. Here is a very simple example of such a structure:
stress and deformation depend not together anymore linear. The lateral deformation is increased because of the lateral displacement by the vertical force. This cantilever column is a geometrically nonlinear structure or in other words, there is a stability problem.
For the detection of such a structure is no longer enough, a simple stress analysis. It must also be performed on a stability proof. Could be conducted so that the forces are determined on the deformed system, ie, after second-order theory, and then a stress analysis is conducted.
The calculation for second-order theory with modern structural analysis software, today no more no art. If one can expect to first-order theory, then that has some real advantages. Instead of load groups can also use load combinations. on the exact difference between load groups and load combinations I've ever written here etws.
But at what point is a stability proof necessary? It may be that the vertical force is very small compared to the horizontal force. The decisive criterion is the critical load factor. If it is greater than 10, then, the influence of second-order theory are neglected. Is it 10 less, then a stability check is performed.
So, now is clear, what one needs the critical load factor. The second part is about what the exact number and how to calculate with RF-STABLE the critical load factor.
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