Crane Barge FEA

A shipyard client requested a detailed finite element analysis (FEA) for a crane foundation on a new crane barge.  DMS provided detailed analysis, including support for regulatory compliance, vendor interface, and adjustments for production schedule.

DMS achieved the ultimate goal:  a scientific analysis that supports the client’s plans.  More importantly, this analysis presents ample information to defend and support the plans.  The FEA offers proof of safety.  

 

 

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Project Scope

This project required a detailed knowledge of design standards for offshore cranes, FEA modeling experience, and an understanding of the vessel mission.  First DMS determined the forces from the crane, and then applied them to the vessel.

1.  Crane Load Cases

DMS worked with the Client to apply offshore standards and develop crane load cases for the inland barge.  This required close cooperation with the Client to apply reasonable criteria.

 

Load Case Calculation

Finite Element Analysis (FEA)

2. FEA Quality

DMS developed a finite element analysis (FEA), which included approximately 1/4 of the barge.  This included full detail of all barge plating, stiffeners, and bulkheads.

The DMS analysis applied several extra steps to guarantee simulation quality:

  1. Included a validation study, which compared FEA to experimental results.
  2. Included a mesh independence study to prove we had the correct FEA settings.
  3. Included a sub-model to analyze critical sections of the structure in more detail.  The submodel reduced modeling costs, and allowed DMS to increase confidence in the results.
  4. Provided a detailed FEA report that specified all the major decisions and assumptions.

In the end, DMS delivered a thorough analysis ready to confidently justify the safety of the crane foundation.

 

FEA Displacement Map

3. Weld Analysis

DMS also analyzed the welds at critical joints in the crane foundation.  We applied the stresses from the FEA to determine the weld size and guarantee that nothing was oversized.

4.  FEA Results

DMS produced results showing several common FEA outputs:

  • Displacement plot:  understand how the structure bends and what direction.
  • Von-Mises Stress plot:  What is the “average” stress level in the structure.
  • Safety Factor plot:  Are we under safe limits for the material.  Accounts for changes to material and different regulatory limits within the same model.
  • Principal stress plot:  Another method of examinging maximum stress.

DMS provided these details for every load case, plus numerical summaries.  Our reports are never short on information.

Safety Factor Plot

Customer Satisfaction

DMS delivered reliable engineering support, which our Client saw in several areas.

1. Production Support

One major issue for this analysis was the schedule.  As a shipyard, our Client needed to work with fast schedules and keep production moving.

DMS supported this effort with weekly meetings.  At one point, the preliminary analysis hinted that the structure may be undersized.  DMS immediately notified the Client to prevent any rework in production.  We worked with the Client to identify the regions at risk and ensure production could continue on the rest of the vessel.  At all stages in the analysis, DMS was ready to ensure engineering supported production.

2. NO Cost Overruns

DMS offered this project under a fixed price contract, which removed all concerns for cost overrun.  At several points, DMS needed to enhance the FEA model or provide additional calculations.  Other engineering firms may charge for each of these changes, sparking dread of change orders.  At DMS, all these changes were inclduded in the original price.  The final invoice exactly matched the quoted cost.

We have the experience to anticipate challenges from FEA, and included that in our plans.  Problems arose, and DMS adapted to fix them.  No hassle, just solutions.  

 

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