Civil Engineering - Steel Structure Design - Discussion

The question is incorrect or incomplete because it has not mention whether to tell - theoretical or recommended value of effective length. As per theoretical value of effective length the answer will be "l". But. As per recommended value of effective length the answer will be "1.2l".

On other hand this question can be considered a tricky one, since the optional value "0.67l" and "0.85l" doesn't exist in place it is "0.65l" and "0.8l". Moreover "1.5l" couldn't b the answer since there is no where mention the partially restrained against rotation condition.

So this is also incorrect. "2l" can also not b the correct one because your its only applicable for 2 conditions for which you can refer your book or notes.

Thank you!

@All.

I will explain this in easy way;

Held in position= it can't move.
+
Restrained in direction = can't rotate
= fixed one end.

Effectively Restrained in direction = can't rotate.
+
Not held in position = it can move.
= roller.

Therefore support conditions are one end fixed and another one roller.
Theoretical value is 1 and the recommended value is 1.2.

In IS-456:2000(Table-28) for the given condition.

Theoretical value of L (eff) = L.
Recommended value of L (eff) = 1.2 L.
As per IS :800;2007(Table-11).
L(eff)=1.0L.
Hence given Answer is absolutely correct.

One end fixed other end Restricted in rotation but not held in position.
Theoretical (SOM) = 1.0L.
Recommended (RCC) = 1.2L.

Since, 1.2 L is not in option hence L will be the answer. Answer (A) is correct.

Ans [D].

When both end of a column is restraint and one end is not in position then effective length may be 1.5L or 1.2L conditionally but according to options 1.5L will be the answer.

Effectively held in position and restrained against the rotation at one end and the other end is restrained against the rotation but not held in position:

Effective length = 0.80 L.

In any steel structure book recommended vale is given but theoretical is not mentioned. So by default we will understand that recommended value is asked. Recommended value is 1.2L.

Effectively held in position and restrained against rotation at one end, and at the other end restrained against rotation but not held in position.

Effective length = 1.2 L.

Ans should be 1.2L as one end is fixed and other end is allowed to move in horizontal direction only so as per IS 800:1984 Clause 5.2.2 the ans should be 1.2L.

In IS-456:2000 for the given condition.

Theoretical value of L (eff) = L.

Recommended value of L (eff) = 1.2 L.

Hence given Answer is absolutely correct!