Definition of the horizons
From the structural point of view, the horizontals, or floors, can be single or double frame. Single frame floors are ideally designed considering a unitary strip free from any transversal connection, therefore under load ideally they should exhibit a cylindrical deformation, but this almost never happens.
This behavior highlights the need to carefully establish the structural design parameters. Simple rules suggest keeping the ratio between the free span of the floor and its thickness in the range 18-20 in order to limit deformability. By limiting the deformability it is possible to avoid stress concentrations produced by non-structural elements and therefore the onset of crack patterns.
In single-frame floors, the interaction at the edges is an aspect that should definitely be considered. In fact, the structures parallel to the warping, therefore which do not constitute direct support, constitute a real transversal constraint, which gives rise to internal stresses and therefore possible cracking states. The problem can be solved by forming ribs or in cases of high stresses by creating a structural joint along these directions.
The warping direction is certainly an aspect of interest to the designer. Generally there is a tendency to alternate the warping direction in order to maintain a uniform distribution of the load on the various floors.