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Unbraced Length Ratio (Minor LTB) SAP 2000

Unbraced Length Ratio (Minor LTB) SAP 2000

Unbraced Length Ratio (Minor LTB) SAP 2000

(OP)
I am designing a steel structure which holds the hollow core slab on first floor as you can see in attached file so my question is that the sap is considering the unbraced length ratio in minor axis for the beam is 3 and beam is failing can I changed the beam unbraced length ratio to 1. This beam is supporting the 320 mm deep hollow core slab.
When I changed unbraced length ratio to 1 manually beam is working comfortably with 40 percent ratio.
Please see the attachment for more clarificatio

Thanks in Advance

Regard's
Ammar

RE: Unbraced Length Ratio (Minor LTB) SAP 2000

A couple quick comments
1. I couldn't open the attachment.
2. Do you have a question?
3. Lateral Torsional Buckling (LTB) is not sensitive to weak axis unbraced length. It is the effected by the unbraced length of the element (flange) in compression.
4. Software does not know how the structure will be assembled and fastened. Often times, software takes the conservative route and assumes members are unbraced as the default. It is not uncommon for an engineer to specify the unbraced length in the software.

RE: Unbraced Length Ratio (Minor LTB) SAP 2000

(OP)
thanks for your kind reply. i am trying to attached the file again but i dont know why it is not accept attachment how i can send you file?
my question is that does the unbraced length ratio in minor axis can increased from value 1 ?
my beam is supporting the hollow core slab can i assume that my beam has enough resistance against lateral torsional buckling in minor axis in this condition?
SAP is considering unbraced length value of the beam is 3 in minor axis how this values come ? however SAP considering the value in major axis is 1 ,
can i changed the unbraced length value in minor axis 3 to 1 , however beam is fixed supported from both ends?

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