100ft span Hollow Steel ARCH design 6

[cad1009]

Gents please help me out.
i am designing a Steel hollow Arch Gate structure. Arch is 100ft support to support with 30ft height.
Arch is serving the purpose of Entry gate with no dead load on top except facade glass pannels.

I am modeling the Arch in STAAD. to design the pipe section what should be LZ definition for Arch.
Support to support distance is 100 ft and Arch curved length is 130ft.

in my Opinion LZ (bending length) for design should be 130/2 = 65 ft.
Please see the pic attached for reference.

https://files.engineering.com/getfi...470b-4a30-8020-3ce283568e65&file=Untitled.jpg

 

[BAretired]

I don't really understand your output. Why do you have so many buckling modes? Anyway, according to the following article, you are nowhere near having a buckling problem.

http://help.solidworks.com/2012/English/solidworks/cworks/buckling_load_factor.htm

BA