Steel Designer splits the compressive design of a member into two design checks. You may choose to check the slenderness of a member and/or its compressive stress.

When checking or designing members for compression, it is necessary to specify the effective length and unbraced length of the member.

To determine the critical buckling load for a member, it is necessary to enter an effective length to indicate the type of restraint on the ends of the member. The effective length is given by an effective length factor multiplied by the length of the member. The effective length may be different for buckling in the major and minor axis directions. The effective lengths are given by

Lx=Kx*L and Ly=Ky*L

Where L is the length of the member and Kx and Ky  are the two effective length factors for the major and minor axes respectively.

The initial values of Kx and Ky are 1.0.

The slenderness is measured as:

See also: Unbraced Length

To set the properties for compression

Ø  Select the required members in the Frame window

Ø  Choose Compression… from the Design menu

Either

Ø  Click on the icons for the end conditions in each direction

Or

Ø  Type in values for Kx and Ky

Ø  Type in values for Lcx and Lcy

Ø  Click OK

If you choose a standard end condition, the recommended Kx and Ky values will be automatically entered for you.