When forces act upon an object at rest without changing this state of rest, these forces and counterforces are in equilibrium (Newton: action = reaction). The theory of equilibrium of forces is called statics. The equilibrium of forces must also be ensured for constructions so that they will not collapse. Static calculations serve for determining material, construction, and dimensioning of the bearing structures. The dead load of the bearing structure, additional loads occurring permanently or periodically, statically or dynamically (e.g. non-bearing elements, snow, traffic, wind, earthquakes, etc.) as well as the nature/stability of the ground are parameters to be considered. For an official approval, an authorised person (e.g. civil engineer, stress analyst) must establish this so-called proof of stability and it must include the prescribed proof of fire resistance of the bearing structure.
