Columns may be made of plain concrete if their unsupported length does...
Columns may be made of plain concrete if their unsupported length does not exceed their least lateral dimension by three times.
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Columns may be made of plain concrete if their unsupported length does...
Explanation:
Columns are vertical compression members that transfer loads from the superstructure to the foundation. Columns are generally made of reinforced concrete or steel. However, in certain situations, plain concrete columns may also be used.
According to IS 456:2000, the unsupported length of a column made of plain concrete should not exceed its least lateral dimension by more than four times. This means that if a column has a lateral dimension of 300 mm, its unsupported length should not exceed 1200 mm. If the unsupported length exceeds this limit, the column may buckle under compressive loads, leading to structural failure.
The reason for this limit is that plain concrete has low tensile strength and is prone to cracking under compressive loads. When a column is subjected to compressive loads, it tends to buckle laterally. If the unsupported length is too high, the column may buckle before it reaches its compressive strength limit, leading to structural failure.
Therefore, to avoid such failures, it is important to limit the unsupported length of plain concrete columns. This limit ensures that the column is strong enough to resist buckling under compressive loads.
In conclusion, the correct answer is option B, i.e., the unsupported length of a plain concrete column should not exceed its least lateral dimension by more than four times.