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1 December 2017

002238

Modeling | Loading

How are unloaded members handled in the load generator?

Answer

In both cases shown in Figure 1, a load of a total of 51 kN acts in the global X-direction. The problem is the different distributions in both cases:

In variant A, the green loads are larger and the red ones smaller, and in variant B, they are reversed. The biggest problem in option A is that the red loads are strangely the same as in the area above, where there are still the intermediate members (green load).

The problem is the yellow-framed surface. Internally, the load of the entire surface is calculated first (51 kN) and then the closed cells (plane which is completely framed by members) are subtracted from it.

Since the area framed in yellow does not represent a cell (the limiting member between nodes 20 and 36 is missing), there is a special case here. The load generator proceeds as follows:

By subtracting the horizontal members, a large virtual cell is created between nodes 23,760,36 and 20. Due to the missing cell mentioned above, it is assumed that the outer members all have a constant load (here 1.6 and 1.0 kN/m) and the remaining load is distributed to the inner members. Thus, in variant A, the green load is higher and the red loads are smaller. To modify this distribution, there is the following option "Apply all members" in the load generator, as shown in Figure 2.

This option creates the missing cell internally and distributes the loads according to variant B. In our blog, there is an interesting post:

http://www.dlubal.com/blog/9034/dlubal-rfem-5-rstab-8-behandlung-von-unbelasteten-staben-bei-der-lastgenerierung/

Keywords

Load Distribution Load generator All members

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