Setting up a rigging design analysis#
Design of a rigging goes hand in hand with a rigging analysis. The design is often updated based on the outcome of the analysis. This is the (in)famous “design cycle”. DAVE is designed to make these design iterations as quick and fun as possible.
Design sketch#
In DAVE the “design” part typically starts with:
Defining the object that needs to be lifted
Defining the liftpoints on it
Loading the crane, hoist and lifting beams
Configuring the lifting beam configuration (grommet protectors, trunnions etc)
Moving all these objects to their approximate relative positions
Creating the rigging items between liftpoints, lifting beams and hook(s)
The steps above define the approximate lifting arrangement. The nodes that were introduced in the previous sections are created especially for this.
Refine,#
The next step is to finetune and optimize it. This involves:
leveling the lifted object by:
changing the (relative) hook elevations for dualcrane lifts
optimizing the lengths of newbuy slings and grommets
adding or removing shackle
selecting different slings, grommets or shackles from available stock.
checking if the the required strength (MBL) is sufficient by:
calculating the occurring loads
defining global safety factors and DAF
defining local (partial) safety factors for slings and grommets
The rigging analysis node is there to assist with these tasks as well as to define the data required for the final step
Rigginganalysis node#
The purpose of the rigging analysis node is to assist with optimizations of the design.
Rigging analysis report#
For efficient engineering it is therefore important to get feedback quickly.
Design rigging
Rigging items
MBLs, lengths, number of shackles
Rigging analysis
Lifting heights
Lifted object tilts
Tensions in rigging items
Rigging analysis report
Run variations cases
Reporting
What is defined where?
What 
Where 
Remarks 

Dual crane 

Hoists 
Node 

Tilt axis of lifted object 
Node 

Hook height difference 
Section 

Friction 

Local/global friction definition per sling/grommet 
Section 

Angle threshold for inclusion in friction loadcases 
Section 
TODO 
Rigging item factors 

Bending factor 
Node 
use tags 
Partial safety factors (DNV) 
Node 

Use coefficient of utilization \(z_p\) instead (IMCA, Eurocode) using user defined interpolation table (note 1) 
Node 

Lifted object 

CoG inaccuracy factor or envelope 
Node 

Global factors  general 

Weight contingency factor 
Node 

Dynamic application factor 
Node 

Global factors  rigging system specific 

Skew load factor 
Node 

override skew factor with variations 
Section 

Yaw effect factor (dual crane) 
Node 

Replace skew factor with length variations 
Section 

Length variation as factor of diameter 
Section 

Matched pairs 
Section 
Alternative calculation of rigging item workingload limits#
Warning
Deviates from the DNV method
Some companies calculate the WLL according to inhouse rules. To cater to that, the DAVE rigging module offers an alternative way to determine the working load limit of slings and grommets.
The formulation is as follows:
\(F_{allowed}\) = \(g \cdot\) MBL/ (\(\gamma_r \cdot z_p\)) [kN]
where:
MBL = minimum breaking load [t]
\(g\) = gravitational constant [kN/t] \(\approx 9.81\)
\(\gamma_r\) = reduction factor
\(z_p\) = coefficient of utilization
Values provided for lifting, consequence, material and wear_and_application factors are not used in this calculation.
Just like in the DNVGL analysis the reduction factor is the maximum of:
bending factor
termination factor
Note that the definition of the termination factor (which is userprovided) may be different.
Coefficient of utilization#
The coefficient of utilization is defined as a function of the rope diameter of the item. This function is provided by the user in the form of an interpolation table. The function stays constant outside the defined range.
Example#
The typical formulation \(z_p = 4  0.018d\) with \(2.25 \le z_p \le 3.33\) is equivalent to the following table:
diameter [mm] 
coefficient of utilization 

<37 
3.33 
37 
3.33 
97 
2.25 
>97 
2.25 
which can be entered as:
\(z_p\) = 3.33, 2.25
d = 37, 97
The formulation from the Eurocode or BS (section 5.3.2) can be entered similarly.