Incorrect cross-sectional area of HSS columns in Robot CSA S16 implementation

[Anonymous]

When using the Canadian steel code, Robot over estimates resistances of HSS members by about 10%.  It appears that the database used by Robot over estimates the cross-sectional area of the HSS sections by 10%.  For example, an HSS 254x254x16 is listed in the CSA S16 steel code as having a cross-sectional area of 13200mm2.  Robot lists this same member as having a cross-sectional area of 14500mm2.

This 10% error can cause over stresses in excess of 20% when considering combined axial compression and bending.

Please review and comment.

[Artur.Kosakowski]

The CISC book I have lists HSS 254 up to 13 mm thickness but making a quick check I think the value from Robot database seems to be correct.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thanks for looking into this Artur.  

Please refer to the attached Robot file.  These columns in this file were cut out of a model of a building that did not agree with our hand calculations.  This file has 3 columns; HSS 305x305x16, HSS 254x254x16 & HSS 203x203x8.  Robot lists the cross-sectional areas of these as 17700mm2, 14500mm2 and 5480mm2.  The CISC manual lists the areas of these sections as 16100mm2, 13200mm2 and 5480mm2.  You will find the section properties under the table for ASTM A500 HSS sections.  I'm not sure where the discrepancy is coming from.

Thanks,
Carl

[Artur.Kosakowski]

G40 vs. A500.

You should use sections from a different family

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thank you Artur,

Yes, I realise that the ASTM A500 are different from the G40 specifications.  The 90% factor is to account for the different tolerance between G40 and ASTM A500.  The ASTM A500 tables in the code have a "Nominal Wall Thickness" and  a "Design Wall Thickness".  For all the ASTM A500 sections, you will find that the "Design Wall Thickness" is 90% of the nominal wall thickness.  It is this "Design Wall Thickness" that needs to be used in the calculations.

Best regards,
Carl

[Artur.Kosakowski · Accepted solution]

In Robot there are two section families for each of these specifications. For the steel design you should use the HASQ one.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.