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Hinged fixed support allows only the rotation of the reference
section. The reaction intersects with the axis of the hinge and in
determining it is decomposed into two components R and R (fig.
x y
1.3 b).
Movable fixing allows moving the reference section parallel to
the support planes. The reaction consists of the force R that is
perpendicular to the support planes and fixing moment M (fig.
1.3 c).
Immovable fixing excludes any movement of the reference
section. The reaction consists of the force (it can have a different
direction), which is usually decomposed into two components R
x
and R and fixing moment M (fig, 1.3 d).
y
It is also a possible variant of the support fixing possessing
elastic malleability (fig. 1.3 f).
The question of the fixing nature that is solved by an engineer
at the stage of choosing a design scheme is very important. The
excessive schematization of work of support fixing simplifies the
solution of tasks, but reduces the accuracy of the results and vice
versa.

1.2.4 Modeling loadings

External forces are classified according to the method of
application and the nature of the action on the body (fig.1.4).
According to the nature of the action on the body external
forces are divided into static and dynamic.
Static load is a loading at which the acceleration of the body or
its parts is absent, or is so small that it can be neglected. Such load
occurs when the applied force to a body is slowly increasing from
zero to the final value.
Dynamic load is called loading in which there occur a
significant acceleration of the body or its parts and related inertial
forces that should be taken into account.

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