Types of solicitation

Let us now look at the typology of the stresses that act on the structures we are comparing. We can identify two types:
1) internal solicitation
2) external solicitation
We now define the Saint-Venant beam theory and its response behavior to the various types of stress. This will allow given the analogy with our structural model (plant plus bar) to understand the way of working totally different from the single plant.

Theory of the SAINT VENANT beam

The theory of the Saint-Venant beam, based on the Principle of de Saint-Venant, is the set of laws taken from the French engineer Adhémar Jean Claude Barré de Saint-Venant.
It is indispensable for the Science of Constructions, as it allows us to know the states of tension and deformation at a point of a section of a beam in equilibrium (whose research is called the de Saint-Venant problem). By applying the hypotheses posed by the de Saint Venant model it is in fact possible to study with satisfactory results the following cases:
• Centered compression or normal traction: the section is subjected only to a normal tensile or compressive stress applied in its center of gravity.
• Flexion: the section is subjected to a bending moment which acts according to a main axis (x or y).
• Deviated or compound bending: the section is subjected to a bending moment which acts according to the x axis and to a bending moment acting according to the y axis.
• Cut
• Twisting
• Bending pressure
• Deflected pressure deflection