The main purpose of the columns is to transfer the vertical loads to the foundations. However a part of the horizontal actions (wind action) is also transferred through the columns.
In multi-storey buildings, the columns are heavily compressed and they are designed for buckling
Variable profile sections can deliver a certain architectural dynamism to the design of these columns.
Formed from standard sections or plates, these columns have as their main characteristic variable lengthwise dimensions which can optimize their structural function.
Beams spread the vertical loads and are mainly subject to bending. The beam section must therefore present sufficient stiffness and strength in the vertical plane.
There are many different types of beam, as shown in the below table. Amongst these, composite beams are particularly well suited to multi-storey buildings.
When combined with steel, the concrete works in compression and the steel (mainly) in tension: the outcome is a system that offers good mechanical performance, both in terms of resistance and stiffness.
A bracing system is a secondary but essential part of a steel structure. A bracing system serves to stabilize the main girders during construction, to contribute to the distribution of load effects and to provide restraint to compression flanges or chords where they would otherwise be free to buckle laterally.
In order to avoid bracing between the beams, it is possible to design rigid-jointed continuous frames. Multi-storey buildings with a load-bearing structure formed of rigid frames
often require an increase in the column section and sometimes in the beam
Since ensuring stability by frame action is less economical than by bracing, a
combination of the two systems can provide an efficient and balanced solution.
It is possible to have frames in one direction and to use bracing for stability in
the perpendicular direction.