The effective height of free standing non-load bearing wall and column respectively will be:
🔬 Understanding Effective Height and Support Conditions
The effective height (Hₑꜰ) is a crucial concept in structural design, particularly for compression members like walls and columns. It represents the equivalent height of a pin-ended member that would have the same buckling load. It is calculated by multiplying the actual height (H) by a factor that depends on the end support conditions.
Free Standing (Cantilever): The term "free standing" describes a member that is fixed at its base but is completely free and unsupported at its top. This is also known as a cantilever condition. It is the least stable support condition and results in the largest effective height.
⚖️ Detailed Analysis of IS 1905 Provisions
The question asks for the effective height of both a free-standing wall and a free-standing column. These values are specified in IS 1905: Code of Practice for Structural Use of Unreinforced Masonry.
(d) 2.0H and 2.0H
Why it's correct:
• For a Free-Standing Wall: According to Table 4 of IS 1905, a wall that is provided with lateral and rotational restraint at the bottom but is free at the top (a cantilever wall) has an effective height of 2.0 times its actual height (2.0H).
• For a Free-Standing Column: The same principles and table apply to masonry columns. A cantilever column, fixed at the base and free at the top, also has an effective height of 2.0 times its actual height (2.0H).
Therefore, the factor is the same for both the wall and the column under these conditions.
Analysis of Other Support Conditions:
- 1.5H: This factor is sometimes specified in codes for a wall or column that is fixed at the base and has its position fixed at the top, but is not restrained against rotation (fixed-pinned).
- 1.0H: This is the factor for a member that is hinged at both ends (position is restrained, but rotation is free).
- 0.75H: This is the factor for a member that is fixed at both ends (restrained against both position and rotation), such as a wall supporting an RCC slab.
💡 Study Tips for Effective Height
- Free Standing = Cantilever = 2.0H: This is the most important association to memorize for masonry design as per IS 1905. It represents the most unstable condition and thus the highest factor.
- More Restraint = Lower Factor: The more support a member has, the smaller its effective height factor. A member fixed at both ends (0.75H) is much more stable than one fixed at only one end (2.0H).
- Walls and Columns are Similar: In the context of effective height calculations for simple compression members, the rules for walls and columns are often identical for the same support conditions.