Effective Length Method

The application of the Effective Length Method (ELM) within SCIA Engineer can be summarised as follows:

  1. Imperfections

  2. Effective Lengths

  3. 2nd Order Analysis

 

1) Imperfections

Within article C2.2b the AISC 360-22 code specifies the use of notional loads to represent imperfections based on a nominal

initial story out-of-plumbness ratio of 1/500.

This effect can be defined as " Initial Global Geometrical Imperfections" of H/500, where H is the story height.

2) Effective Lengths

As specified in Table C-C1.1 of AISC 360-22 the effective length Lc is taken KL.

For the calculation of the effective length factor K reference is made to "Annex B: Calculation of buckling ratio".

3) 2nd Order Analysis

As a final step a 2nd Order " Nonlinear calculation" can be executed after which the Steel Code check can be run to validate the structure.

This approach is valid for design by LRFD. For design by ASD reference is made to AISC 360-22.