Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Steel Design Codes
	Subarea:	AISC
	Original Author:	Bentley Technical Support Group

The following are the results from the same file, first using 2010 then using 2016.

In 2010 all is green and safe.

In 2016 all is unsafe.

Is there some new parameters that need to be considered?

Both files attached for reference.

.communities.bentley.com/.../AISC2016.STDcommunities.bentley.com/.../AISC2010.STD

This is happening due to the fact that STAAD.Pro is computing the slenderness for tension differently when designing as per the AISC 360-16 than what it used to do before. It is using the max of LY, LZ and the physical member length as the unsupported length for the slenderness check for tension. This is based on the logic that tension slenderness is checked mainly for protection against inadvertent damage to the section during fabrication, transportation or erection as indicated in the Commentary highlighted below. Since during transportation/fabrication/erection the restraints may not be available and the full length of the member could be unsupported, to be on the conservative side we are using the maximum as indicated above.

You may actually by-pass the slenderness check in tension, if you do not need to account for this check by setting the TMAIN parameter to 1 and in that case, you will find that all the members would pass the code check. A modified file is attached for your reference

communities.bentley.com/.../AISC2016_5F00_rev.STD

Starting from STAAD.Pro version 22.10.00.153 a new design parameter named TSL has been added for the AISC 360-16 code, using which users can specify the unsupported length of the member to be used for calculating the tension slenderness. When TSL is specified, the slenderness for tension is calculated by dividing TSL by rmin ( min radius of gyration for the cross section). This would give users more control over the slenderness check when it comes to tension members.