Beperkingen en statische bepaalbaarheid

The equilibrium of the system is defined not only by its equations but with the help of constraints. Constraints refer to the restrictions on the motion of a system.

If a system is held by a minimum number of constraints to ensure equilibrium, it is said to be statically determinate.

For such a system, the unknown reaction supports can be estimated using equations of equilibrium.

If additional redundant supports are added to the system to maintain equilibrium, it becomes statically indeterminate. This means that number of constraints acting on the system is greater than the number of equations of equilibrium available for their solution.

On the other hand, consider a member AB connected to two pin supports at points C and D, such that the lines of action of reactive forces are concurrent at point C.

The applied load will tend to make the beam partially constrained, since the equilibrium equation will not be satisfied for the loading conditions.

Similarly, when all the reactive forces are parallel to each other, it results in improperly constraining.