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FAQ 002903 EN-US 04/11/2019

# Why are the results of bars and bars different in design?

This is because the effective lengths or buckling lengths of bars and staff sets differ. While the actual length of the bars is used for the proof of stability, for bar sets it is the length of the combined bars.

example
The frame shown in the picture (see picture 1) consists of a bar divided into 4 bars of equal length. In addition, a set of rods is created for the 4 rods. The proof of stability is carried out for both cases according to the substitute rod method.

When dimensioning the bars, the length is calculated to be 1.00 m. In contrast, the rod set is 4.00 m long (see Figure 2). Of course, the difference in lengths has an effect on the stability rating, which means that the workloads also differ (see Figure 3)

It is also not recommended to calculate all bars and sets of bars in a design case, as this leads to falsified results.