Nonlinear FEA Assurance of a Temporary Load Introduction Frame for a Heavy Lift Operation

Project context
A temporary steel load-introduction frame was designed to enable lifting of a large industrial asset using strand jacks. The permanent structure was not designed to accept direct lift loads, requiring a removable frame bolted to existing stiffeners.

Given the temporary nature of the works and the consequence of failure, the lifting contractor required independent confirmation that:

• Load sharing would occur as intended

• Local overstress would not occur at bolt groups and attachment plates

• Second-order effects would not destabilise the system during lift synchronisation

Why FEA was essential
Hand calculations could demonstrate global strength but could not reliably assess:

• Load redistribution due to differential jack stiffness

• Local plate bending and bolt-group prying

• Nonlinear contact behaviour at interfaces

Equitus FEA scope

• Fully nonlinear 3D FEA including:

  • Contact interfaces between frame and permanent structure

  • Bolt preload and slip behaviour

  • Geometric nonlinearity to capture second-order effects

• Parametric studies covering:

  • Jack stiffness variation

  • Minor out-of-plane misalignment

  • Partial loss of load in one lifting line

Outcome

• Confirmed overall stability but identified unexpected local plate overstress

• Enabled targeted stiffening without increasing frame mass

• Provided Mammoet with a defensible engineering basis for execution sign-off