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Structural Reliability

September 18, 2019

Issue

One of our industrial minerals clients installed a new shiploader and elevated conveyor structure at in 2011.  During a static inspection of the Shiploader in 2015, Andvare identified that the elevated wharf conveyor structure was exhibiting significant deformation, particularly in the truss module that was at the time supporting the tripper.  An interim repair solution was developed and installed to alleviate some of the load entering into the truss chord structural splice connections.  The report also advised that this interim solution should be superseded with a full repair option within a two to three year period.

The repair of the elevated conveyor structures were complicated by a number of issues including:

  • Prior failure of the bolted splice connections of the main conveyor truss modules meant that the truss had sagged considerably from design service height;
  • The truss had an angled mitre at the centre span instead of the true pre-camber specified on the design drawings;
  • The shiploader and trusses had a very limited out-of-service window for repairs; and
  • The tripper loads on the trusses were significantly higher (approximately 150%) than the original design assumptions.

Solution

Andvare provided Engineering, Fabrication and Procurement Services to ensure the solution met the needs of the client in terms of quality, delivery time and price.

  • Development of load combinations compiled in accordance with the requirements of AS1170.0 and as varied by AS1418 and AS4324.1;
  • Structural designs audited using FEA and the rectified structure checked against fatigue design criterion under AS4100;
  • Complete development of detailed design drawings including update and modification of client drawings;
  • Development and fabrication of jacking equipment and methodology to temporarily remove the sag from the truss modules during installation of the sub truss installation.
  • Andvare’s European division headed the fabrication, procurement and logistics to deliver a complete turn-key package to site;
  • Provision of a completed MDR including all weld quality and inspection reports, material certifications, dimensional control and surface treatment reports; and
  • Andvare’s project team provided on-site engineering support and overseeing of the works and ensure compliance with design intent.

Benefits

  • Increased the fatigue life of the structure significantly beyond the 30 year requirement;
  • Reduced the permanent deflection in the truss and along the tripper rail by more than 50%;
  • Returned the structural capacity of the elevated structure to code requirements.