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Concept# Statically indeterminate

Summary

In statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations – force and moment equilibrium conditions – are insufficient for determining the internal forces and reactions on that structure.
Mathematics
Based on Newton's laws of motion, the equilibrium equations available for a two-dimensional body are:
: \sum \mathbf F = 0 : the vectorial sum of the forces acting on the body equals zero. This translates to:
:: \sum \mathbf H = 0 : the sum of the horizontal components of the forces equals zero;
:: \sum \mathbf V = 0 : the sum of the vertical components of forces equals zero;
: \sum \mathbf M = 0 : the sum of the moments (about an arbitrary point) of all forces equals zero.
In the beam construction on the right, the four unknown reactions are V''A'', V''B'', V''C'', and H''A''. The

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