The idea is to transfer (Dead and alive) building loads to the ground. This can be achieved through a couple of methods: arches, dome structures, trusses, etc. Using a mixture of flat roofs and columns is one of these methods. A column is normally considered to be a vertical load bearing part of the structure. It's designed to transmit a compressive load and its function is to carry gravity loads (dead weight of structure or live load of people or just stuff like snow, warehouse goods). It could be concrete, steel, wood, even ice if you live in the arctic. Its shape could be round, square, rectangular. In the case of a one-story building, it would support the roof. Columns are usually equally spaced to give uniform support to the upper structure. Hence, it should be realized that the failure of a column results in the collapse of the entire structure. A Column transmits the load from ceiling/roof slab and beam, including its own weight, to the foundation. There are many types of columns used in construction field. Such as: Circular Column, L and T shaped Column, Square or Rectangular Column, Tied Column, Axially Loaded Column.
1. L and T shaped Column: Generally, the L-shaped column is utilized in the corners of the boundary wall and has similar characteristics of a rectangular or square column. The T-shaped column is utilized based on the design requirements of a structure. It is widely used in the construction of bridges.
2. Circular Column: Circular columns are mostly used in piling and elevation of the buildings for aesthetic purposes. In a circular column, more than 4 longitudinal steel bars are used as a reinforcement bar and its bending resistance is generally higher than the square or rectangular column.
3. Tied Column: This is usually constructed from reinforced concrete. Longitudinal reinforcements are confined within closely spaced tie reinforcement. If ties are spaced too far apart, the column will experience shear failure and barreling in between ties. It is estimated that 95% of all columns in buildings are tied column.
4. Square or Rectangular Column: They are commonly used in the construction of buildings and heavy structures. It is much effortless to construct and cast rectangular or square columns than circular ones because of the ease of shuttering and to support it from collapsing due to pressure while the concrete is still in flowable form.
5. Composite Column: These columns consist of structural steel or cast iron column enclosed with concrete, reinforced with longitudinal as well as spiral reinforcement. Composite columns are widely used in truss structures to avoid the corrosion of steel. This type of column has more adequate strength with a fairly small cross-section, in addition, to exhibit good fire performance. Columns are not a wise proposition for up to three stories unless it is an earthquake-prone area. They are required for high rise buildings for reducing the thickness of walls. Columns withstand quakes because they cope with tensile forces caused by the vibrations of a quake. Columns transmit loads to a much reduced area and are a disadvantage. But this disadvantage is neglected in buildings of more stories, where thickness of walls becomes too much without columns.
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