1. A D-region in a reinforced concrete member is defined as a portion
a) Where strain varies linearly through the depth
b) Within a distance equal to the member height *h* from a discontinuity
c) Governed by St. Venant's principle
d) With uniform stress distribution
2. Which statement about bottle-shaped struts is false?
a) They require transverse reinforcement to control splitting cracks
b) Their effective strength *fce* uses *βs* = 0.75
c) They have uniform width along their length
d) They are idealized with a 1:2 taper at ends
3. A nodal zone resisting three compressive forces is classified as
a) C-C-C node
b) C-C-T node
c) C-T-T node
d) T-T-T node
4. The effective compressive strength *fce* for a bottle-shaped strut with transverse reinforcement is
a) 0.85 × 0.60 *f'c*
b) 0.85 × 0.75 *f'c*
c) 0.85 × 1.0 *f'c*
d) 0.85 × 0.80 *f'c*
5. For deep beams, the minimum horizontal reinforcement *Avh* must satisfy
a) *Avh* ≥ 0.0025 *bws*
b) *Avh* ≥ 0.0015 *bws*^2
c) *Avh* ≥ 0.003 *bws*
d) *Avh* ≥ 0.83 *f'c* *bwd*
6. If the anchorage length of a tie exceeds the extended nodal zone, the ACI Code requires
a) Increasing the strut width
b) Using hooks, mechanical anchors, or extending the bar
c) Reducing the concrete strength
d) Ignoring the anchorage requirement
7. A hydrostatic nodal zone is designed to ensure
a) Equal compressive stresses on all faces
b) Maximum tensile stress at the node
c) Minimal use of reinforcement
d) Zero strain compatibility
8. According to ACI Code 11.8.3, the maximum nominal shear strength *Vn* for a deep beam is
a) 0.83 *f'c* *bwd*
b) 1.1 *f'c* *bwd*
c) 0.17 *f'c* *bwd*
d) 0.75 *f'c* *bwd*
9. Transverse reinforcement in bottle-shaped struts is primarily used to
a) Increase axial load capacity
b) Resist longitudinal splitting due to spreading compression
c) Reduce nodal zone dimensions
d) Replace tension ties
10. An efficient strut-and-tie model prioritizes
a) Maximizing the number of tension ties
b) Minimizing energy by using stiff compression paths
c) Uniform nodal zone sizes
Answer (1)
Let's go through each of the questions one by one to provide clear and accurate explanations:
A D-region in a reinforced concrete member is defined as a portion: The correct answer is b) Within a distance equal to the member height h from a discontinuity . D-regions (Discontinuity regions) in concrete members are zones where strain distributions are non-linear, typically found near abrupt changes in the geometry or load applications, such as openings or beam-to-column connections.
Which statement about bottle-shaped struts is false? The correct answer is c) They have uniform width along their length . Bottle-shaped struts do not have a uniform width; they are wider in the middle than at the ends, resembling a bottle.
A nodal zone resisting three compressive forces is classified as: The correct answer is a) C-C-C node . A nodal zone where all three applied forces are compressive is classified as a C-C-C node.
The effective compressive strength fce for a bottle-shaped strut with transverse reinforcement is: The correct answer is b) 0.85 \times 0.75 f'c . This value takes into consideration the effective compressive strength reduction factor for struts with confinement provided by transverse reinforcement.
For deep beams, the minimum horizontal reinforcement A_{vh} must satisfy: The correct answer is a) A_{vh} \geq 0.0025 \times b_w s . Minimum reinforcement is required to control cracking and maintain serviceability.
If the anchorage length of a tie exceeds the extended nodal zone, the ACI Code requires: The correct answer is b) Using hooks, mechanical anchors, or extending the bar . To ensure adequate anchorage and prevent failure at the nodal zone, additional measures like hooks or mechanical anchors are used.
A hydrostatic nodal zone is designed to ensure: The correct answer is a) Equal compressive stresses on all faces . A hydrostatic nodal zone ensures uniform stress distribution on all faces of the node.
According to ACI Code 11.8.3, the maximum nominal shear strength Vn for a deep beam is: The correct answer is a) 0.83 \times f'c \times b_w d . This provides an upper bound on the shear strength for design purposes, ensuring safety and stability.
Transverse reinforcement in bottle-shaped struts is primarily used to: The correct answer is b) Resist longitudinal splitting due to spreading compression . Transverse reinforcement helps to control potential splitting and cracking due to the spreading nature of compression in bottle-shaped struts.
An efficient strut-and-tie model prioritizes: The correct answer is b) Minimizing energy by using stiff compression paths . The efficiency of these models comes from minimizing material usage and energy through optimal load paths.
