Slenderness Ratio of Channel in Bending and Compression

[ltimmis80]

Yesterday I was checking the size of a PFC that has already been installed as a pipework support column in a factory. The PFC was circa 3.5m high and was acting as a cantilever, unrestrained about both the major and minor axis. The pipes are supported approx 90mm away from the face of the channel (on the minor axis). Doing the calculation by hand, I found the slenderness ratio was circa 400 and outside the scope of the bluebook. I also checked in the code (BS5950) and the table only went as far as 350. However, when I put the channel into the Tedds design software it performed the check using App C1 of BS5950 and passed the section. Although the loads we are talking about here are small, this unnerved me a little as I would have thought that there would be some sort of upper limit on the slenderness ratio allowed. The bluebook seems to indicate it's 180 and the code 350, however, I can't find a clause that specifically states what, if any, this upper limit should be.

Does anyone know why the bluebook only allows slenderness ratios up to 180 and why the table in the code stops at 350? I'm just really curious now and want to understand the logic behind it.

Thanks

Ltimmis

 

[racookpe1978]

I'm sorry - I don't recognize your PFC term.

 

[racookpe1978]

Poly/Plastic/Polymer Channel maybe?

 

[Ingenuity]

Parallel Flange Channel

 

[ltimmis80]

Sorry, yes, I meant a parallel flange channel. Any ideas anyone?