In modern practice, pillars are most often made of reinforced concrete, less often of steel and even less often of wood or other materials.
1. Reinforced Concrete Pillars
Monolithic reinforced concrete pillars can be formed with different cross-sections: square, rectangular, polygonal or circular. The reinforcement of the columns is composed of longitudinal rebars and stirrups of different density, corresponding to the static load. The mould can be traditional wooden shutter, or modern framed panel formwork. A cast-in-situ reinforced concrete pillar can also be built with stay-in-place permanent formwork. This permanent formwork can be a brick casing or built from concrete column shuttering blocks. In the case of the brick casing solution, the casing is built in stages, a reinforcement is placed and the cavity is filled with concrete in phases. The desired height is reached in sections of 1.00 to 1.20 metres. In the case of concrete shuttering blocks, pour the concrete in one step after the full height has been reached and the reinforcement has been properly positioned. The elements must also be wetted before concreting and during the finishing operations. The temporary bracings can be removed only after the concrete has fully hardened. Finally, precast reinforced concrete pillars can be also placed. These are typically also placed in precast pocket foundation above the monolithic spread footing.
2. Steel Pillars
Steel can be used to build lightweight, heavy-duty and small cross-section structures. They can be manufactured in cold bent or hot rolled sections.
Steel pillars can be made with different cross-sections:
- single columns can have I, H, C, Z or hollow profiles,
- columns can be formed by connecting several profiles by struts,
- truss structures can also be created from L profiles and horizontal or inclined struts,
- finally, we can also build columns of circular profiles.
A base and head plate are welded to the pillar to connect the steel stem to other elements. The connection can be reinforced with steel plates (stiffeners), which are also fixed by welding. The base and head plates can be used to bolt the column to the concrete base or to a steel beam. Steel structures should be protected against rusting by galvanising or powder coating. In addition, fire safety considerations may require the application of various fire retardant coatings.
3. Wooden Posts
Modern wooden pillars can also be designed with a variety of cross-sections.As with steel piers, they can be made from a single piece of wood, factory-glued laminated beams, a combination of these, assembled from different beams with spacer blocks or tightly connected. In most modern practices, wooden columns do not meet the footing through a timber lower sill but are loaded directly onto a concrete spread footing or a reinforced concrete grade beam. Direct contact between the two is dangerous for wood because prolonged contact with moisture can lead to wood decay. Therefore, the wooden posts always start above ground level, connected to the foundation slab or the spread footing through steel column shoes. In addition, in modern practice, wooden columns must be made flame- and fungus-proof before they are installed. This process is called impregnation. A protective coating against the weather (sun, precipitation) can be applied by varnishing.
