Effective Length verification

How to verify the effective length of the column after analysis for a steel member?

If a cantilever beam having effective length 2L how can i validate the result of the member that it takes the effective length for analysis?

Thanks in advance.

  • For the column you can see KL/r values int he steel design output (in the program or in the output report).

    For the beams, the user can specify longer unbraced lengths if desired using the UNB and UNT design parameters typically.



    Answer Verified By: Beni R 

  • Effective length is not reported as the analysis result. It is the reported as the steel design result. By default, the effective length is taken by Staad as the member length unless you specify the effective length by LY or LZ parameter.
    However, if you want Staad to automatically take the effective length while designing, you can use the AISC -ASD code and click on the check box. Once you click on the checkbox, Staad would take the effective length factor based on the method specified in the AISC nomogram.

    Effective length is not reported as the analysis result. It is the reported as the steel design result. By default, the effective length is taken by Staad as the member length unless you specify the effective length by LY or LZ parameter.
    However, if you want Staad to automatically take the effective length while designing, you can use the AISC -ASD code and click on the check box. Once you click on the checkbox, Staad would take the effective length factor based on the method specified in the AISC nomogram.

    However, you can use Staad buckling analysis feature to verify the the effective length factor of the vertical cantilever under point axial load on it tip is "2L".

    For this, please see the explanation and calculation below.

    The model is created with its both end pinned and its tip is free to move transitionally.

    After performing the buckling analysis, the lowest Buckling load factor (BLF) is 

    Now lets make is purely vertical cantilever by modified its boundary condition.

    So, after performing the analysis of the cantilever column, the lowest BLF is 1.918.

    Now, Buckling load, Pcr = BLF* Applied Load

                                 

    Now for the first case, 

     Pcr1= BLF1*L

    For the second case, 

    Pcr2= BLF2*L

    Also,

     Pcr1 = pi^2*E/(K1*L)^2

     Pcr2 = pi^2*E/(K2*L)^2

    Comparing the above equations

    (K2/K1)^2 = BLF1/BLF2

    (K2/K1) = Sqrt (7.491/1.918) 

    (K2/K1) = (2/1)

    which concludes that the effective length factor for the vertical cantilever is 2



    Answer Verified By: Beni R 

  • Thank you for the response Seth Guthrie,Geeky Biswa

    BENI