Global analyses are essential for large thin-shell structures such as ships, bridges and aircraft. The analysis models are usually put together like most complex structures, in sections. This makes it easier to keep tabs on input, and also make it possible to work on local load cases within the model.

  

Mid section   One of the forward sections   Half model   Full model - usually symmetrical geometry, but assymetrical loads are possible

 

In this particular job, the intention was to save structural weight for future vessels built  in a series by considering different structural arrangements (the prototype vessel was already in service).   

 

Critical panels   Critical panels in keel area   Critical panels in upper decks   Critical panels - other load cases

     

Results for plates, frames, etc, can always be studied separately. Here are some frame results for different load cases and arrangements. The results always show the most critical areas.

 

Critical girders   Critical transverse frames   Critical transverse frames   Critical transverse frames - details

 

What you get is not always what you expect! It looked as though some of the bow frames and panels could collapse under wave loads. A report came in soon after we had delivered our report that the prototype vessel had suffered damage at exactly these frames in a storm.

  

Panel buckling   Frame collapse   Critical panels   Critical panels - worst case stresses

 

We work mostly with ships. But most other shell structures can be analysed in the same way. All we need to agree on are the loads and the standards to be applied.

 

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