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

I am designing a beam as per AISC 360-16 code.  How do I specify the unbraced length for lateral-torsional buckling (LTB)?

In STAAD the AISC 360-16 code utilizes steel design parameters UNL and UNR to specify the unbraced length for lateral-torsional buckling.  UNL is the unbraced length for the left extreme flange and UNR is the unbraced length for the right extreme flange.  The program determines which extreme fiber is in compression for each load case (right or left), and based on that uses the applicable UNL or UNR unbraced length for the purpose of computing LTB capacities.  

The UNL and UNR parameters appear in the design parameters dialog box as follows:

*Please note - in the absence of the UNL and UNR parameters the program assumes their values are equal to member length.