Two Point Lift with Rotation Aug 2022

Couple aspects

I present a few analytical aspects as well as real life examples.

Consider a module or a vessel to be lifted at Lugs L1 and L2.

The red axes represent horizontal (GX) and vertical (GY)
The blue axes are affixed to the lifted object
Note that the location of the object CG is arbitrary; the CG is not required to be aligned with Lug L1
As Lug L2 is lifted, θ increases and the object is rotated
Of course, the loads at the two lugs vary with θ
Ultimately all the object design weight is carried by Lug L1

The following chart illustrates the loadings for the range of θ from zero to 90 degrees. I built this spreadsheet in 2008. I have never seen anyone present these graphs.

These next screenshots provide data for four key points in the lift rotation. In my spreadsheet, the maxima for shear and tension are found using Excel Solver. In lift calculations, there is no need for two decimal places results, so I round off to the nearest degree or 0.1 kip.

Maximum tension in each lug

Maximum tension at Lug 1 (head lug)
Note cells B14 and B28
At θ = 90 degrees, L1 tension is 180.4 kips

Maximum tension at Lug 2 (tail lug)
Note cells B14 and C28
At θ = zero degrees, L2 tension is 76.1 kips

Maximum shear in each lug

Maximum shear at Lug 1 (head lug)
Note cells B14 and B25
At θ = 9 degrees, L1 shear is 105.6 kips

Maximum shear Lug 2 (tail lug)
Note cells B14 and C25
At θ = 59 degrees, L2 shear is 47.5 kips