CivilLab · Study Aid

Plastic Collapse Mechanisms

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What am I seeing?
  • A plastic hinge forms where the moment reaches Mp; the section then rotates at constant moment.
  • Collapse needs enough hinges to turn the structure into a mechanism, so redundancy plus one.
  • The load factor comes from equating external work to internal work at the hinges.
  • A fixed ended beam carries twice the central point load of a simply supported one, 8Mp/L against 4Mp/L.
  • For a frame, several mechanisms are possible and the lowest load factor governs.