Concrete Beams Vs. Concrete Pillars

Concrete

• Concrete is very strong when compressed but not so strong when pulled. In other words, the compressive strength of concrete is much greater than its tensile strength. This property makes concrete particularly well-suited to columns or pillars, since in these applications it's supporting heavy weights that lie directly overhead. Concrete's lower tensile strength, however, makes it more challenging to use in beams, especially since concrete is also a very dense and thus very heavy material.

Reinforcement

• Reinforced concrete makes concrete beams possible. The most common approach is embedded steel beams called rebar. Steel possesses high tensile strength and thus serves to compensate for the lower tensile strength of the concrete in the beam. Sometimes the beam may be prestressed, in which case it is kept compressed by stressing the steel before the concrete is poured or in some cases after it has hardened.

Supports

• Concrete beams typically span multiple supports. For example, a beam may be connected to multiple concrete pillars or columns along its length. It might seem as if pillars would be much simpler to design since only compression is involved. Often, however, pillars are subjected to some bending forces as well, depending on how the weight above them is positioned. In a scenario such as an earthquake, for instance, a concrete pillar would very quickly become subjected to strong lateral stresses. So concrete pillars are often reinforced too.

Column Design

• While still important, the flexural strength, or strength in bending, is less critical for concrete columns than it is for beams. Unlike beams, concrete columns are not generally "prestressed." It's important, however, to make sure that the concrete column or pillar has a confined core, meaning that horizontal steel tie bars link the vertical steel bars inside the concrete. This kind of arrangement can support a much greater load. The tie bars may be arranged in either a tiered or spiral pattern.