By Milo S. Ketchum

  • If a picture is worth a 1000 words, then a simple model is worth 1000 calculations.

  • There are only a few basic structural systems for post and beam structures, but for shell structures, there are thousands, each requiring a unique approach to design.

  • The supports for a shell are more important than the shell.

  • Shell structures can usually be understood as a set of beams, arches and catenaries and can be analyzed by that approach.

  • For any shell structure, there will be a simple method of analysis that can be used to check the more precise analysis.

  • Stiffest path concepts are useful in understanding shell structures.

  • Support the edges of shells if they are already supported visually by masonry walls or window walls.

  • Do not throw away all you structural intuition when you design shell structures.

  • For ordinary structures, an adequate preliminary design should be within 10 percent Shell structures can be estimated to within 5 percent because the only usual unknown is the amount of reinforcing.

  • Shell structures can carry relatively large point loads.

  • If you rush into computer calculations without a thorough study of the structure with several possible arrangements, then you may not get the best structure.

  • Shell structures get their strength by shape and not by high strength of materials Do not push stresses to their limit.

  • In case of doubt, reinforce. Shell structures are very complex and carry forces by many paths.

  • Shell structures, because of their complexity and unfamiliarity require a large lead time for developing the design.

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