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Lateral buckling force

Lateral buckling force

Lateral buckling force

(OP)
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.

RE: Lateral buckling force

2% of the axial load is the generally accepted rule for the lateral brace force.  

RE: Lateral buckling 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 here.

RE: Lateral buckling force

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.  

RE: Lateral buckling force

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.      

RE: Lateral buckling force

(OP)
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?

RE: Lateral buckling force

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.

RE: Lateral buckling force

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 member?

RE: Lateral buckling force

I mean EI/(AL), the unit is k/in as well.

RE: Lateral buckling force

I don't use the spec too often but that sounds like a reasonable conclusion.  I believe you mean AE/L.

RE: Lateral buckling force

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.

RE: Lateral buckling force

You're right, UcfSE. EA/L is the axial stiffness of a prismetic member. Thanks

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