Question:
As per IS 456:2000, a compression member may be considered as short when both the slenderness ratios (l/r and l/b) are:
A) Less than 12
B) Less than 15
C) Less than 20
D) Less than 25
Explanation:
According to IS 456:2000, Plain and Reinforced Concrete Code of Practice, Clause 25.1.1, a compression member may be considered as short when both the slenderness ratios l/r and l/b are less than 12.
Where, l = Effective length of the column r = Least lateral dimension of the column cross-section b = Width of the column section
For short columns, the effects of slenderness and lateral instability do not need to be considered as the column fails by direct crushing.
Therefore, option A is the correct answer, as per the slenderness ratio limits given in IS 456:2000 for identifying short columns.
Options B, C and D suggest higher slenderness ratio limits which are not correct as per the code. For ratios above 12, the column cannot be considered as short, and second-order effects need to be checked.