Lifting Lug Design Query 2

[sammcc]

Hi everyone, I am trying to self teach some theory around the design of lifting lugs and doing a Google search doesn't throw up that much info, however I have found a report from David T Ricker which is pretty self explanatory, however I have a question which I hope someone can answer. On p152 he is talking about the 3rd failure mode being "shear whereby the pin may push out a block of steel as it attempts to plow through the edge of the pin" The formula for the approximate shear load he gives is:

Pu = 2(0.4)Fy et

My question is what is the 0.4? Hopefully someone can answer this very simply for me!!

 

[steele6707]

I have used that guideline in the past. I am writing from memory, so anyone else feel free to correct me. That article is based on the AISC (9th Edition). Allowable shear stress is 0.4 Fy (Eq. F4-1). The et term should produce an area which would be multiplied by 2 faces times an allowable shear stress. You may also wish to look at ASME BTH specification (especially if OSHA may have any jurisdiction). This is very similar to AISC 9th edition and makes it easier to use different safety factors. There are also different requirements for different classifications of lifters. I have the 2008 edition but there may be a later version. As I recall the cost was about $50 US when I bought mine. BTH is for design and there is another spec for operation. There are some spreadsheets that will aid in lifting lug design.

 

[JAE]

Well, sammcc refers to "Pu = ". That looks more like LRFD does it not?

 

[corus]

Von Trescas yield stress is twice shear, so the limit for shear is half the yield stress, multiplied by a factor. In this case it reduces to 0.8 x 0.5 yield or 0.4 x yield.

 

[WillisV]

That reference, though definitely good guidance, is a bit outdated. Lifting lug design should be performed per ASME BTH-1 (2011 latest version)

 

[sammcc]

think I will need to buy the ASME standard although, I am not really using this for anything other than experience, I just like to understand what I'm doing!

 

[sammcc]

I have purchased the ASME document and as I go through it, it appears to be quite different from the Ricker article which I belive is based on AISC ASD manual 9th edition. What is the standard or are both methods really down to personal choice, from looking at them it appears that they would yield (excuse the pun) different results?

 

[WillisV]

ASME is the standard to use for lifting lugs - not AISC.

 

[TLHS]

Plus the ASME standard is actually really good as far as design standards go. It both explains why you're doing things and walks you through how to do them. Most seem to just do one or the other.

 

[sammcc]

Trouble is, I am finding the AISC one easier to understand!!