2571x
002903
2019-04-11

Question

Why do the results of members and sets of members differ in the design?


Answer:

The reason is that the effective lengths or buckling lengths of the members and sets of members are different. While the actual length is used for the stability analysis in the case of members, the length of the summarized members is used in the case of sets of members.

Example

The frame shown in Image 01 consists of a horizontal beam that is divided into four equally long members. Furthermore, a set of members is created for the four members. The stability analysis is performed according to the equivalent member method for both cases.

For the member design, the program calculates with a length of 1.00 m in each case. In contrast, the set of members has a length of 4.00 m (see Image 02). This difference in length certainly affects the stability design, which means that the design ratios are also different (see Image 03).

In addition, we do not recommend calculating all members and sets of members in a single design case, because this leads to falsified results.