Correct Answer - Option 2 : 60
Concept:
Unsupported length:
Unsupported length is the clear distance among the member capable of providing lateral support to the column. For the pin-ended column, it is the distance between the hinges. The unsupported length has several lengths that may appear in various directions and should be used for computing the respective slenderness ratio.
According to the IS 456: 2000:
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Clause 25.3.1 said that The unsupported length between end restraints shall not exceed 60 times the least lateral dimension of a column.
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Clause 25.3.2 said that If in any given plane, one end of a column is unrestrained, its unsupported length shall not exceed \(\frac{100\ b^2}{d}\).
Where, b = width-of that cross-section
d = depth of the cross-section measured in the plane under consideration.
