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

Increasing the NSF value in Steel Design does not change the Failure Ratio for a member, Why?

In the design input parameters, I set NSF to .85 for my steel design. The design output result showed a failure ratio of 1.063 on Member 1. I then proceeded to change the NSF parameter to 1.0. This time, the design output result showed the same failure ratio of 1.063. It seems that nothing has changed. I increased the net section factor by 0.15, but the stress ratio hasn't changed? 

The NSF value has an effect only on allowable axial tensile capacity, and the actual tensile stress.

If axial tension, or axial tension plus bending, are not what determine the critical condition, changing the value of NSF will not have any impact on the failure ratio. For example, if the critical failure condition for a member is compression, changing NSF will have no impact.

Check to see what the critical condition is. It will show up in the form of expressions such as:

AISC H1-1 or Slenderness, etc.