Observation Platform


In order to study the natural wildlife, a small elevated observation platform was constructed with just a single center post. There is a small hinged door on the floor to access the platform. Only one person is on the platform at one time.

What is known:

  • Maximum weight of the observer is 300 lb.
  • The center supporting post is a 6x8 wood timber (check Structure Shapes appendix for exact cross section size).
  • The platform overall dimensions are 6 feet by 7 feet.
  • The observer can move around the platform, but the furthest location from the center is 3 feet and 2.5 feet as shown in the diagram (6 inches from either railing)..

Top View of Platform


What is the maximum stress in the center wood post due to a 300 lb person standing on the platform at one of the corners?


  • The observers weight will cause unsymmetrical bending.
  • Find the moment around both axes that define the plane of the platform.
  • Find the moment of inertia for both materials around both axes.
  • Use the unsymmetric beam bending stress equation

  • Check the compression stress due to the axial load of the observer on the center post.
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