Steel Column Verification

[Anonymous]

I am trying to appraise an existing steel column to BS 5950.I have modelled the column in three parts as first screenshot, and set the supermember 1001 comprising bars 100,200 and 300.

The first lift height is 7.837m, with effective length for compression buckling and lateral torsional buckling as 0.85*7.837 =6.662m  ( Weak axis)

The second lift height is 6.010m, with effective length for compression buckling and lateral torsional buckling as 0.85*6.010 = 5.109m( Weak axis)

The strong axis is unrestrained over the height and effective length is 1.0*13.847=13.847m

I have set the ‘K9 Column’ design parameters based on these design assumptions:-

Please note that I cannot override the sway to non sway?

However the design calculations do not appear to use the 0.85*Length for the weak axis slenderness or LT buckling. Please refer to following picture.

Can you give any tips why the steel design module does not appear to utilise this?

Another query is, does RSA only report the most onerous 'lift' of a column. In this case, the upper portion?

I have attached model   

Column Model

Cheers

[Artur.Kosakowski · Accepted solution]

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Please note that I cannot override the sway to non sway?

Sway or non sway matters only when the coefficient is calculated automatically based on the stiffness of adjoining elements. In this case you enter the values directly e.g. 0.85; 1 etc.

However the design calculations do not appear to use the 0.85*Length for the weak axis slenderness or LT buckling. Please refer to following picture.

Can you give any tips why the steel design module does not appear to utilise this?

As the values you entered e.g. 0.85 are incorrectly replaced by others e.g. 1.0 (see the line directly below the button you indicated) which you can see when you reopen this dialog after setting the coefficients you want to use. This has to be further investigated by the development team as doesn't work as intended.

Another query is, does RSA only report the most onerous 'lift' of a column. In this case, the upper portion?

Yes, the results are displayed for the location where the obtained ration is the largest but you can run the verification in the indicated point only. In your case it is the bottom part as the local X axes point downwards.

[Artur.Kosakowski]

As the values you entered e.g. 0.85 are incorrectly replaced by others e.g. 1.0 (see the line directly below the button you indicated) which you can see when you reopen this dialog after setting the coefficients you want to use. This has to be further investigated by the development team as doesn't work as intended.

Corrected in RSA 2017 SP2.

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