Statically Indeterminate Structures

 Key Concepts:  Structures with more supports provided than needed to maintain equilibrium of the member are said to be statically indeterminate.  In such a case neither the support reactions nor the internal forces, torques and moments can be determined from the equilibrium equations alone.  Solution combines use of equilibrium, geometry, and load-deflection.

In a Nut Shell:

Statically indeterminate means that the forces in various portions of the structure cannot be

determined by statics alone.  Deformation must also be considered.  Usually there are three

ingredients in a statically indeterminate problem:

 1 Equilibrium 2 Geometry 3 Load-Deflection

The same three ingredients are in any problem in deformable bodies – either statically

determinate or indeterminate.  But in the indeterminate case, they must usually be considered

simultaneously.

More information is required to analyze this type of problem.  Possible statically

indeterminate structures include  axial, torsion and bending members.

The same three ingredients are in any problem in deformable bodies – either statically

determinate or indeterminate.  But in the indeterminate case, they must usually be considered

simultaneously.