Tailing beam design in Dennis Moss's book

[jamesl]

This is a follow-up question on thread 794-103201. Dennis Moss's design manual (3rd edition) gave the force in strut or tailing beams, as well as bending moment coefficients. I can totally follow up one point, two points pick or parallel beams. But those beam frames (3-point or four-point) lost me. I have some questions:
1. How are those forces F1, F2 and F3 calculated. Moss's book gave F1=0.453T, F2=0.329T for three-point. F1=0.5T, F2=-0.273T, F3=0.273T for four-point (why is there a F1?)
2. With those F1, F2 and F3, how to calculate bending moment coefficients for those two cases (three-point and four-point)?
3. When using two tailing lugs, which arrangement is better, Parallel-beams or three-beams?
Thanks.

 

[jte]

jamesl-

I don't have the 3rd edition, but I'm reasonably certain that if you look at "Roark's Formulas for Stress and Strain" (by Young, if you're looking for the lates ed.) you'll find the basis for the constants. In my 6th edition, it is in Chapter 8, Table 17 "Formulas for Circular Rings." What you'll have to do is start with Case 15, "Ring supported at base and loaded by own weight..." for a one point pick. For a two point pick, you split the load and algebraically sum the results around the baseplate. For loads which are resisted vertically at two offset points, you'll have to find a 4th edition. Or you can try to play with Case 4 in the 6th ed.

jt

 

[LSThill]

Team Member

Lifting Lugs & Tailing beam design will be in CODEWARE "COMPRESS" Pressure Vessel and Heat Exchanger Software soon.

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Leonard Thill, Bangkok, Thailand

 

[jamesl]

jte:
Thanks for your comments. As I said in my original post, I did reproduce the results from Moss's book for the one-point and two-point arrangements. I just could not figure out how the lifting load redistribute with beam frames design(three beams forming a triangle or four beams forming a square).

 

[jte]

jamesl-

Like I said, you'll have to find a copy of the fourth edition which includes a case for two offset vertical reactions. Algebraically combine this case with a one point pick case to get the triangle. If your square is vertical and horizontal, combine the two offset vertical reaction case with itself rotated 180°. If your square is a diamond, combine the offset vertical reaction case with the two one point picks you used to develop your two point pick.


jt

 

[jamesl]

jte:
Thanks again for your time. What you said is absolutely right. But that is not what I was asking for. My question is how the load is distributed at the corners of triangle or square. For example, assuming the lift load is T, for one point pick the reaction force on skirt is T; for two point pick, it will be T/2 at each point. I can not figure out those reaction forces for three point or four point pick. As I mentioned in my original post, Moss's book list those forces in the beams, and I do not know how he came up with those numbers.