design category ASTM BTH

[ukengineer58]

Hi can someone list the design categories used for FOS on the material strength. I am reviewing some calcs and comparing them to Europeon standards. I believe there are categories A,B etc...

 

[WinelandV]

It's a bit convoluted when using the Nd factor, but if you just look at 3-1.3.2 [ASME BTH-1-2014] you can see the design philosophy:

For Design Category A lifters, yielding and buckling limit states have a factor of 2.0, while fracture and connection design use 2.4.
For Design Category B lifters, those values are 3.0 and 3.6, respectively.

Please note that is a "v" (as in Violin) not a "y".

 

[ukengineer58]

thanks for the reply. I am based in Uk and we dont use that code. so was trying to compare a set of calcs with out limit state approach. So was trying to understand what category A and B would be. As all i have is 'designed to B' which seems conservative for the case we have

 

[Lomarandil]

Design category B may be the conservative case, but a lot of lifting devices are reused (and abused) frequently over their lifespan, so cheaper to overdesign a little than to put the controls and inspections in place to justify A

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just call me Lo.

 

[ukengineer58]

thats part of my reason. these are one off lifts of a defined known weight. So there is not chance of reuse. its part of a demolition

 

[Lomarandil]

Ah, yes. If it is a one-off lift(say, padeyes welded to the piece being picked) -- that's a perfect example of a category A device. Most demolition is a great candidate for that.



----
just call me Lo.

 

[ukengineer58]

great thanks - thats confirms what i was thinking. thanks for your help..