Structural Engineering & Statics
where the load goes
Series

Three-dimensional equilibrium — the series

One essay so far on this idea, and more questions about it than one essay answers.
  1. Three legs, three equations, one answer. A rigid top on three legs carrying 120 kN at (0.3, 0.2) m. The three equilibrium equations available — one vertical and two moments — leave three unknowns, so the system is exactly determinate and the reactions are 56.8, 13.6, 49.6 kN. Move the load anywhere and the answer moves with it; nothing about the legs' stiffness enters.

    Six equations, and the drawing shows three

    Every essay so far has taken place on a piece of paper, where equilibrium is three equations and a structure is a diagram. The real object has six, the extra three are the ones nobody writes down, and the difference between three legs and four is not a matter of degree.

    part 1 · equilibrium

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