Structure Lift Analysis Software

[Ussuri]

Does anyone know of any commercially available lift analyis software?

In particular something which works in terms of structural line elements and not FEA. We have FEA packages that can do it but the timescale is such that there is never time to develop the model.

At the moment we use general frame analysis software for this which works fine when you have slings connected direct to a structure but is no use when you have more complicated arrangements using spreaders and the like.

The problem occurs that the forces are resolved into the components and without an external restraint the stiffness matric becomes non valid. There is no way to take into account the mutiple degrees of freedom associated with rope shackled to rope shackled to rope swinging freely until it reaches equilibrium.

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[richay]

You might see if "Ultra Marine" is still around. They used to have a program called OSCAR that would do this.

Richard Ay
COADE, Inc.

 

[iuston]

In my company they use SACS for lifting analysis, it is commercial and widely used in offshore analysis

http://www.sacs-edi.com

 

[bertyboy]

Ussuri, I have found a good free spreadsheet program,
Sling Pro, available from engineeringspreadsheets.co.uk
that does 4 leg sling design in accordance with the major
offshore codes. You select the code, then the load and
apex angle then select the 3 components :- Master link
assembly, wire rope, and shackle on the basis of
component load capacity >= the applied load.
Otherwise if this program can't do it I use a
standard stuctural analysis program.

 

[NeilAA]

Modelling of spreader bars can be achieved in a general frame analysis.

As you have stated, there are effectively degrees of freedom which need restraint to achieve equilibrium, but in practice need to move laterally. The way to deal with these is to use a soft spring as a support for the relevant degree of freedom as opposed to a rigid restraint. This enables a relatively large movement with small reaction force and the finite element matrix remains stable.

You do need to have a reasonable idea of what the lift configuration should look like to model it initially. Any large forces or displacements at the springs would indicate that your initial guess of the behaviour was badly wrong, and you should consider adjusting the model to prevent inaccuracies in the analysis.