Lateral torsional buckling - fork bearings

[Anonymous]

Hey guys. I have been trying to calculate on an IPE600 beam subjected to an point load in the middle which is 279 kN.  The length is 10 meter. It has also fork bearing in the supports and in the middle.

 However i can't get the right M_cr. I hope you can help me. See attached files.

The correct M_cr is 1911 kN*m and is calculated like this M_cr=m_1*(E*I_z)/l^2)*h_t. I get 417 kN*m.

[Artur.Kosakowski · Accepted solution]

If you have a fork support in the middle you should add a internal bracing for LTB of the top flange at this location.

 

Mcr is calculated in this way:

http://forums.autodesk.com/autodesk/attachments/autodesk/351/2832/1/Formula%20F2.png

See also:

http://forums.autodesk.com/t5/robot-structural-analysis/critical-moment/m-p/3335273

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thanks you very much. But i do also have fork supports at the supports, should i also have bracings there? And is it possible for me to change the way m_cr is calculated?

[Artur.Kosakowski · Accepted solution]

The ends of a bar are treated as bracing points by default. You cannot change the way Mcr is calculated but you can enter your own value as shown in the forum topic I indicated in my previous answer.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.