FAQ 000299 EN-US

# When calculating the effective lengths of a simple structural system, for the first buckling mode I obtain an effective length Lcr,y that is too great.What is the reason for this?

Lcr,y is too great in the first buckling mode because of the following reason.

In RSBUCK, the lowest critical buckling load is calculated first.

For example, the buckling load is obtained for a hinged column (Euler buckling mode 1 with HE-B 300) for the buckling about the z-axis. With this buckling load, the effective length Lcr,y is determined retroactively.

If you also want to obtain the correct effective length for Lcr,y, you must also look at the second buckling mode. To do this, set the number of buckling modes to be determined to 2.

In the second buckling mode, you obtain a higher buckling load (sway about the y-axis), from which you obtain the correct buckling load Lcr,y.

In RSBUCK, it is necessary to calculate several buckling modes to obtain results for the individual directions.