Lifting Beam Design
Lifting Beam Design
(OP)
I am load rating 2 previously constructed lifting beams. I have found that ASME B30.20 requires a 3.0 safety factor against yielding. Does OSHA require a more stringent safety factor? I have found on the internet that Ontanio OSHA requires a 5.0 safety factor against failure.
Furthermore, what is your opinion of how the satefy factors should be implenmented?
To give a couple of easy examples of how I interpret the proper implentation of the Safety Factors is:
Bending: Fb=.6Fy/3.0 and
Shear rupture: Fv=.3Fu/5.0
Does anyone see this a different way?
Furthermore, what is your opinion of how the satefy factors should be implenmented?
To give a couple of easy examples of how I interpret the proper implentation of the Safety Factors is:
Bending: Fb=.6Fy/3.0 and
Shear rupture: Fv=.3Fu/5.0
Does anyone see this a different way?






RE: Lifting Beam Design
RE: Lifting Beam Design
I instead multiplied my live loads by 1.8. Since ASD uses an approximate 1.67 factor for yield, 1.8*1.67=3.0. This satisfies the 3.0 safety factor requirement.
Anyone have comments on this approach?
RE: Lifting Beam Design
Assume 36 ksi steel:
Fy=36
Your allowable stress=36ksi/3=12ksi
Fu=58
Your allowable shear rupture=58ksi/5=11.6ksi
Now if the ASME standard uses ultimate loads..
Apply LRFD load factors to your live and dead loads to get a total load. Use the ultimate strength of the steel, so for 36ksi steel use 58 ksi.
Your allowable yield stress now equals: 58/3=19.33 but your loads are factored.
Does this make sense?
RE: Lifting Beam Design
Practically all of our structural work is "A36". But I understand that much of the material we use is actually dual-certified, with a higher yield strength (maybe 50 KSI, not sure). Anyway, worth checking on.
I'm not sure what you're actually making -it sounds like what I hear called a spreader bar- if so, AISC-ASD may be governed by buckling due to lack of lateral support, or column buckling, rather than by yielding.