User:Eml4500.f08.team.Bengtson/teamHWStaticallydeterminate

The stability of the Electric Pylon
How does one find if something is statically indeterminate? When the amount of equations is not sufficient for finding all the unknowns of the system. $$   * \sum \vec F = 0$$ : the vectorial sum of the forces acting on the body equals zero. This translates to

Σ H = 0: the sum of the horizontal components of the forces equals zero; Σ V = 0: the sum of the vertical components of forces equals zero;

$$\sum \vec M = 0$$ : the sum of the moments (about an arbitrary point) of all forces equals zero. Reference used

If we look at the electric pylon we find that it has two nodes but four beams coming out of the nodes. Thus the system is not made of two force beams at the reaction (constrained) sites and the amount of equations is less than the unknowns.

Also, as the system is a frame system, the rotational displacements cause bending moments within the beams.

In summary, each of the four beams at the constrained sites has an axial force and a bending moment associated with it. This makes a total of 8 unknowns, and there are only 3 equations to solve for these unknowns using the statics method.

Thus the electric pylon is statically indeterminate.