lateral buckling force

huangyhg

lateral buckling force
hi everyone. i'm trying to calculate the force magnitude of the lateral buckling of a slender steel girder. i know that my beam is going to buckle so i will use lateral support attached to a wall but i dont know how to calculate the strenght of this lateral supports because i need thid force. thanks for your comments.
2% of the axial load is the generally accepted rule for the lateral brace force.  
you should follow the aisc's bracing strength and stiffness requirements.  the specification is a free download from aisc.org and can be found
also see aisc lrfd 3rd edition...specification chapter c, use relative bracing formula, not the nodal.  the required force in the brace will pop out of the pbr equation.  
ucfse
i went to the aisc web site but didn't seem to find information on bracing and stiffness requirements.  could you provide a little more information on the title of the document.
i work with wood trusses and deal with questions about truss bracing a lot.  the question comes up when bottom chord bracing is not provided.      
because of space and money, i couldn't use a non compact section so i decided to use a slender section girder near to a concrete beam. the distance between both is almost 6 inches. i have to use lateral support in order to avoid lateral torsional buckling but i need to calculate the load applied to these supports. i will find out what is wrriten on the aisc-lrfd about this subject. is there another way to find out this load?
on the site page from the link i provided, under related files, you find a link to the 2005 specification.  section c1.2 of the 2005 specification directs you to appendix 6: stability bracing for columns and beams.  that may or may not help you with requirements for wood.
ucfse,
i'm not sure the meaning of the "brace stiffness" there. fox example, i calculated betabr = 6 kip/in from eq. (a-6-2) in the appendix. does this mean the 6k/in is the minimum el/a value of the bracing   
i mean ei/(al), the unit is k/in as well.
i don't use the spec too often but that sounds like a reasonable conclusion.  i believe you mean ae/l.
ucfse
thank you for the additional information on the aisc web site.  i down loaded appendix 6,which will be helpful to me, in some applications.