According to IS 800: 2007, what is the effective length of prismatic compression member of length l, if rotation and translation both degree of freedoms are restrained at one end of member and at other end of member transnational degree of freedom is allowed and rotational degree of freedom is fixed?
- A0.8l
- Bl
- C1.2lCorrect
- D2l
Solution
Concept
Effective Length of Compression Members
Formula
KL = 1.2L
Step-by-step solution
1. Identify end conditions: One end is fixed against translation and rotation (Fixed end). The other end is allowed to translate laterally but fixed against rotation (Sway/Sleeve end). 2. Refer to IS 800:2007 Table 11 for effective length factors of compression members. 3. For a member fixed at one end and restrained against rotation but free to translate at the other, the effective length factor K = 1.2. 4. Calculate effective length: Effective Length = K × l = 1.2l.
Explanation
According to IS 800:2007 Table 11, when a column is completely fixed against movement and rotation at one end, and allowed to move laterally but fixed against rotation at the other end, the recommended effective length factor is 1.2. Therefore, the effective length is 1.2l.
Shortcut
To quickly remember IS 800:2007 effective length factors (KL), memorize the standard baseline hierarchy from most restrained to least restrained: - Fixed at both ends (no sway): 0.65l - Fixed at one end, hinged at other: 0.8l - Hinged at both ends: 1.0l - Fixed at both ends with sway (translation allowed at one end): 1.2l - Fixed at one end, free at other (cantilever): 2.0lShortcut Rule: Whenever rotation is prevented at both ends but sway/translation is permitted, add 0.2 to the standard pinned condition (1.0l + 0.2l = 1.2l).
Common mistake
Many students confuse the recommended design effective length factor (1.2l) with the theoretical value (1.0l) or mistake this boundary condition for a fixed-pinned column (0.8l).
Correct answer: C) 1.2l