A lifting lug is a lifting and handling accessory generally welded to a part to hoist it with a crane / overhead crane hook. It is possible to buy standard models or to manufacture them yourself with sheet metal.
* dynamic factor = with ξ = 0.3 for fixed crane or on rails and ξ = 0.6 for crane bridge.
The quantity of effective lifting points may be less than the quantity of real lifting points if the system is not balanced. It is recommended not to exceed 2 effective lifting points in the calculations if no specific balancing system is used.
The force in one lifting point does not necessarily correspond to the mass to be lifted divided by the number of effective lifting points. The inclination of the slings will cause a horizontal reaction that will amplify the force. The multiplier factor can be calculated as follow : With α the angle formed between :
the two slings connecting the most distant points if no specific balancing system is used.
the two slings connecting points side by side if a specific balancing system is used (like a lifting beam).
no specific balancing system is used
a lifting beam is used
In the case of intensive use of the lifting point, an additional calculation of the fatigue strength must be carried out.
Extract of the standard EN 1993-1-1 §6.2.3 Ultimate Limit States - Resistance of cross-sections - Tension
(2.b) the design ultimate resistance of the net cross-section at holes for fasteners : (6.7) where:
Anet is the net area of the cross section.
fu is the ultimate strength.
γM2 is the partial factor for resistance of cross-sections in tension to fracture.
Extract of the standard EN 1993-1-8 §3.10.2 Deductions for fastener holes - Design for block tearing
(1) Block tearing consists of failure in shear at the row of bolts along the shear face of the hole group accompanied by tensile rupture along the line of bolt boles on the tension face of the bolt group. (2) For a symmetric bolt group subject to concentric loading the design block tearing resistance, Veff,1,Rd is given by: (3.9) where:
Ant is the net area subjected to tension.
Anv is the net area subjected to shear.
fy is the yield strength.
γM0 is the partial factor for resistance of cross-sections whatever the class is.
Extract of the standard EN 1993-1-8 §3.6 Design resistance of individual fasteners - Bolts and rivets
(Table 3.4 - bearing resistance) where:
k1 is a coefficient that takes into account distances to edges perpendicularly to the applied force.
αb is a coefficient that takes into account the distances to the edges parallel to the applied force.
d is the nominal crane hook diameter.
t is the the thickness of the lifting lug.
the 0.6 factor is added to take into account the effect of 150% oversized hole (like a slotted hole - Note 1 Table 3.4).
Extract of the standard EN 1993-1-8 §3.13 Connections made with pins
(2) Pin connections in which no rotation is required may be designed as single bolted connections, provided that the length of the pin is less than 3 times the diameter of the pin, see 3.6.1. For all other cases the method given in 3.13.2 should be followed : Geometric requirements :
The DXF (Drawing eXchange Format) is a CAD data file format developed by Autodesk to allow transfer of information from AutoCAD to other programs. This makes it possible to directly manufacture the part or integrate it into another technical drawing.