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

Why is it that when I change the yield strength ratio of steel using Ry in the material definition it is not reflected in the AISC 341 seismic design checks?

The yield strength ratio Ry (as well as the tensile strength ratio Rt) in the material definition are used by the Connection Design module only.  They do not have any bearing whatsoever on the steel design results. 

FYI, the Ry and Rt properties in the material definition appear graphically as shown below:

 

In the input command file, these properties look like this:

If you wish to change the yield strength ratio of steel for design within STAAD.pro, you must use the SGR design parameter shown below:

Simply specify the desired grade of steel, then assign the SGR parameter to the members in your model.  When you run the analysis the program will use the Ry value corresponding to that grade of steel when performing the seismic checks as per AISC 341 (which will be reflected in the TRACK results shown in the output file.)