BCE Reinforced Concrete Design 2 — Questions and Answers
Question 1: In ACI 318, the development length (ld) for a straight deformed bar in tension depends primarily on which factors?
- Bar diameter, concrete strength, steel yield strength, cover, and spacing (Correct answer)
- Bar diameter and concrete strength only
- Steel yield strength and lap splice length only
- Bar diameter and stirrup spacing only
Correct answer: Bar diameter, concrete strength, steel yield strength, cover, and spacing
Development length depends on bar diameter, fy, f'c, concrete cover, bar spacing, transverse reinforcement, coating, and location (top vs. bottom bars).
Question 2: Two-way flat plate slabs transfer shear directly to columns through which failure mechanism?
- Diagonal tension beam shear
- Punching shear around the column perimeter (Correct answer)
- Flexural compression failure
- Bond failure at slab-column interface
Correct answer: Punching shear around the column perimeter
Flat plates are susceptible to punching shear failure where the slab 'punches' through along a truncated cone or pyramid around the column.
Question 3: The effective depth 'd' in a reinforced concrete beam is defined as:
- The total height of the beam
- The distance from the compression face to the centroid of tension reinforcement (Correct answer)
- The distance between the centroids of tension and compression steel
- The height minus the cover thickness
Correct answer: The distance from the compression face to the centroid of tension reinforcement
The effective depth d is the distance from the extreme compression fiber to the centroid of the tension reinforcement, which is the lever arm for internal couple calculations.
Question 4: What is the purpose of temperature and shrinkage reinforcement in a one-way slab?
- To carry flexural loads in the span direction
- To control cracking perpendicular to the span direction due to temperature changes and concrete shrinkage (Correct answer)
- To increase the slab's punching shear capacity
- To provide anchorage for the main flexural bars
Correct answer: To control cracking perpendicular to the span direction due to temperature changes and concrete shrinkage
Temperature and shrinkage steel is placed perpendicular to the main flexural reinforcement to control cracking caused by concrete shrinkage and temperature variations.
Question 5: In the design of reinforced concrete columns, a column is classified as 'short' when:
- Its height exceeds 3 meters
- Slenderness effects can be neglected (klu/r ≤ 22 for braced frames) (Correct answer)
- Its reinforcement ratio exceeds 4%
- Its cross-section is square
Correct answer: Slenderness effects can be neglected (klu/r ≤ 22 for braced frames)
A column is short (non-slender) when the slenderness ratio klu/r ≤ 22 for braced frames, meaning second-order (P-delta) effects are negligible.
Question 6: Which reinforcement configuration provides the most ductility in a tied reinforced concrete column?
- Widely spaced large ties
- Closely spaced spiral reinforcement (Correct answer)
- Single perimeter tie with no intermediate bars
- Diagonal cross-ties only
Correct answer: Closely spaced spiral reinforcement
Spiral columns provide significantly greater ductility than tied columns because the continuous spiral confines the concrete core, maintaining load-carrying capacity after the shell spalls.
BCE Reinforced Concrete Design 2
In ACI 318, the development length (ld) for a straight deformed bar in tension depends primarily on which factors?