Lifting Lugs with ASME BTH-1-2008
Lifting Lugs with ASME BTH-1-2008
(OP)
Hi Everyone,
Baseed on thread507-273125: Design of lifting lugs, I am working on designing a standardized set of lifting lugs using ASME BTH-1-2008.
For now, I am working on a single case and detailing the calculations.
The lug is as per figure C3-3. I have also attached a sketch.
I need to vary the angle of the applied load in the plane of the lug so it will be usable from 0º to 90º from the position shown in figure C3-3.
When analysing the welds, I can determine the tensile and shear limits of the weld (0º and 90º) however, when the angle is anything but 0º, a moment is created at the interface between the lug and existing structure requiring a flexion analysis in the strong axis as per 3-2.3.
The problem I have is that it's not clear to me if I am dealing with a compact or non-compact section as per table 3-1.
I also need to determine this for a flexion analysis in the weak axis. Any help would be appreciated.
Baseed on thread507-273125: Design of lifting lugs, I am working on designing a standardized set of lifting lugs using ASME BTH-1-2008.
For now, I am working on a single case and detailing the calculations.
The lug is as per figure C3-3. I have also attached a sketch.
I need to vary the angle of the applied load in the plane of the lug so it will be usable from 0º to 90º from the position shown in figure C3-3.
When analysing the welds, I can determine the tensile and shear limits of the weld (0º and 90º) however, when the angle is anything but 0º, a moment is created at the interface between the lug and existing structure requiring a flexion analysis in the strong axis as per 3-2.3.
The problem I have is that it's not clear to me if I am dealing with a compact or non-compact section as per table 3-1.
I also need to determine this for a flexion analysis in the weak axis. Any help would be appreciated.






RE: Lifting Lugs with ASME BTH-1-2008
b could be the distance from the root of the lug out to the center of the hole. t is the thickness of the lug.
Back-calculate a t required to ensure a compact behavior and you go from there.
RE: Lifting Lugs with ASME BTH-1-2008
Thanks for the reply.
I don't have AISC's table B4.1 however it seems like ASME BTH-1 table 3-1 has a similar entry.
"Legs of single angle struts; legs of double angle struts with sparators; unstiffened elements, i.e., supported along one edge"
Which has the following limits for width/thickness ratio (b/t):
- Compact = 0.38*sqrt(E/F_yf)
- Noncompact = 0.45*sqrt(E/F_yf)
Would you agree that b would be the total width minus the hole diameter, i.e., the weakest section?
b is defined as: "width of a compression element"
RE: Lifting Lugs with ASME BTH-1-2008
In your case, I would see the b distance as the straight vertical edge to the base (center of hole to base weld line).
RE: Lifting Lugs with ASME BTH-1-2008
RE: Lifting Lugs with ASME BTH-1-2008
RE: Lifting Lugs with ASME BTH-1-2008
For a square plate, like your lug, local buckling is not possible. Therfore it is inherently compact. I think JAE's recommendation to check AISC B4.1 is conservative and good guidance (I would probably do somethign similar) but I don't think it is 100% necessary.
RE: Lifting Lugs with ASME BTH-1-2008
I'm not sure LTB of a lug could ever happen (unless you had a really funky looking lug), I would probably just use the full plastic capacity of the pad eye. But F-11 is the section you want to check to be thorough.
RE: Lifting Lugs with ASME BTH-1-2008
Could you show your sketch as a pdf file, I can’t see it in the format to showed it. Alternatively, I will survive without see it. Almost invariably, pin bearing, shear and yielding in the area of the pin, and good quality welding detailing controls the design of lifting lugs.
RE: Lifting Lugs with ASME BTH-1-2008
I think what I posted above is correct but WillisV and others posts are right on - buckling isn't really an issue with lugs like this unless the plate is thin and the lug is really long and extended. Even then, I wonder about how much compression would even get into the lug with an angled hanging "tensile" load.
RE: Lifting Lugs with ASME BTH-1-2008
Thanks for your help.
WillisV, Agreed, this makes sense to me despite being a mechie.
NS4U, The 2008 version of ASME BTH-1 I am using is commented and most calculations refer to AISC. I beleive that the ASME code mostly describes certain cases covered by AISC.
dhengr, I will post the .pdf version. The base of my lugs will be wider, however, to be conservative I am designing with a constant width plate for now.
JAE, Still good advice, since I am doing the calcs in Mathcad to semi-automate the design, I am still going to check the section for it's compactness, however there's also a simplified clause for rectangular sections I will check out.
Thanks again, of course further comment is always welcome.
RE: Lifting Lugs with ASME BTH-1-2008
Dik
RE: Lifting Lugs with ASME BTH-1-2008
That's correct.
I select the closest available Crosby G-209 shackle for the load.
The next available drill size will be used to make the hole slightly larger than the pin.
AMSE BTH-1 accounts for the difference in diameter between the pin and the hole.
Regards,