Every building and structure should be so constructed and constructed, that their use is safe and secure. Three conditions are required for the construction of a building: endurance, stability and stiffness. Strength condition means, that both individual elements, as well as structural systems should with a certain safety margin transfer the loads acting on them. The condition of stability is this, that building (building) it does not shift under the action of horizontal forces and does not rotate. Means, that W. < T and Mw < Mu. The holding moment for Mu should be 1,5 times greater than the moment of capsizing Mw. The stiffness condition is to limit the vertical and horizontal displacements of the structure. The lateral deflection value is usually taken as a measure of the building's spatial stiffness.
In longwall buildings (wooden, brick and concrete) The spatial stiffness is provided by the walls placed transversely and longitudinally to the longitudinal axis of the building.
In buildings with a transverse arrangement of load-bearing walls, stiffening walls in the longitudinal direction should be used, while in buildings with a longitudinal arrangement of load-bearing walls, the role of stiffening walls is played by transverse walls.
Load-bearing and stiffening walls are usually connected with each other along the entire height of the building and with the ceilings of individual floors.. For functional reasons, door or window openings are made in the walls.
The external walls of the building are divided into load-bearing, self-supporting and shielding (filling). Bearing walls carry vertical and horizontal loads; the vertical loads from the dead weight of the wall and ceilings are transferred to the foundation, while horizontal loads are transmitted through the ceilings to load-bearing or stiffening transverse walls or directly to the transverse walls. Self-supporting walls work similarly to load-bearing walls. The vertical load, mainly due to the dead weight of the wall, is transferred to the foundation, and horizontal to ceilings or transverse walls. Curtain walls and filling walls transfer the load from the dead weight (Vertical) and horizontal ones directly on ceilings or longitudinal transoms.
In frame buildings, the spatial stiffness may be provided by the following structural systems:
a) frames with rigid knots,
b) frames with articulated joints and vertical and horizontal braces,
c) frames with articulated joints and walls,
d) stiffening walls or shanks.
Mixed stiffening systems can also be used, e.g.. frames and walls or frames and shafts.