RCC Columns – Minimum Diameter of Lateral Ties What is the minimum diameter permitted for lateral ties (column ties) in reinforced concrete columns under standard detailing practice?
-
A4 mm
-
B5 mm
-
C6 mm
-
D10 mm
-
E—
Answer
Correct Answer: 6 mm
Explanation
Introduction / Context:Lateral ties in columns confine the core concrete, restrain longitudinal bars from buckling, and maintain reinforcement geometry during casting. Codes specify a minimum diameter to ensure adequate stiffness and robustness of ties, especially during vibration and handling.
Given Data / Assumptions:
- Member: reinforced concrete column.
- Role of ties: confinement, bar restraint, and geometry control.
- Standard practice: non-seismic, ordinary detailing context.
Concept / Approach:
The minimum tie diameter must be sufficient to avoid yielding or distortion during placement and service. Standard practice sets an absolute lower bound along with a conditional rule that ties should not be less than one-fourth of the largest longitudinal bar diameter; however, the absolute minimum remains a fixed value in millimetres.
Step-by-Step Solution:
1) Identify that ties must be stiff enough to restrain the main bars.2) Apply the basic detailing rule: tie dia ≥ 6 mm and also ≥ one-fourth of the largest longitudinal bar dia.3) Therefore, the absolute minimum permissible diameter is 6 mm.Verification / Alternative check:
Typical bar bending schedules and standard RCC detailing textbooks prescribe 6 mm as the minimum tie diameter in ordinary conditions, while seismic detailing often increases this (for example to 8 mm) in special confining regions.
Why Other Options Are Wrong:
- 4 mm and 5 mm: Too slender for reliable confinement.
- 10 mm: Allowed, but not the minimum; used in heavily loaded columns or seismic regions.
Common Pitfalls:
Confusing seismic provisions with general detailing; ignoring the one-fourth largest bar rule that can govern when main bars are large.
Final Answer:
6 mm