Which of the following is an Obligatory Requirement during the structural layout planning to ensure the ductility of an RC frame in seismic zones?
- AKeeping the column size smaller than the beam size.
- BAligning beams such that their centerlines coincide with the column centerlines to avoid eccentricity.Correct
- CProviding the maximum possible spacing between lateral ties.
- DUsing only plain mild steel bars for main reinforcement.
Solution
Concept
Beam-Column Joint Alignment in Seismic Design
Formula
N/A
Step-by-step solution
1. Read the question regarding structural layout planning for RC frame ductility in seismic zones. 2. Recall that aligning beam and column centerlines prevents eccentricity and reduces localized stress at joints. 3. Compare with the given options and select Option (b) as the correct choice.
Explanation
Aligning beam and column centerlines ensures that forces transfer directly down the center without twisting or creating uneven stress at the joints. Avoiding this eccentricity prevents sudden localized damage, helping the structure flex safely and maintain ductility during an earthquake.
Shortcut
To easily remember beam-column alignment in seismic design, use the rule "Center-to-Center for Zero Eccentricity": - Center-to-Center Alignment: Beam and column centerlines must coincide to avoid load eccentricity. - Zero Eccentricity = Max Ductility: Prevents joint twisting and stress concentrations, allowing the frame to flex safely during earthquakes.
Common mistake
A common mistake is selecting Option A due to a misunderstanding of the "strong-column weak-beam" principle; columns must actually be stronger and generally larger than beams to prevent storey collapse during earthquakes. Another frequent error is selecting Option C, confusing the requirement for closely spaced lateral ties needed for concrete confinement and ductility with maximum spacing, which reduces shear strength and confinement.
Correct answer: B) Aligning beams such that their centerlines coincide with the column centerlines to avoid eccentricity.