Structural Concrete - Hassoun

222 Chapter 5 Shear and Diagonal Tension
SUMMARY
Sections 5.1 and 5.2
The shear stress in a homogeneous beam is v = VQ/Ib. The distribution of the shear stress above the
neutral axis in a singly reinforced concrete beam is parabolic. Below the neutral axis, the maximum
shear stress is maintained down to the level of the steel bars.
Section 5-3
The development of shear resistance in reinforced concrete members occurs by:
• Shear resistance of the uncracked concrete
• Interface shear transfer
• Arch action
• Dowel action
Section 5-4
The shear stress at which a diagonal crack is expected is
v c = V (
bd = 1.9λ √ )
f c ′ V
+ 2500ρ u d
w ≤ 3.5 √ f c
′ M u
The nominal shear strength is
Sections 5.5 and 5.6
V c = v c b w d = 2λ √ f ′ cb w d
1. The common types of shear reinforcement are stirrups (perpendicular or inclined to the main
bars), bent bars, or combinations of stirrups and bent bars:
V u = φV n = φV c + φV s and V s = 1 φ (V u − φV c )
2. The ACI Code design requirements are summarized in Table 5.4.
Sections 5.7 and 5.8
Design of vertical stirrups and shear summary are given in these sections.
Sections 5.9 and 5.10
1. Variation of shear force along the span due to live load may be considered.
2. For members with variable depth,
φV n = V u ± M u(tan α)
d
REFERENCES
1. “Report of the ACI-ASCE Committee 326.” ACI Journal 59 (1962), 121 p.
2. ACI-ASCE Committee 426. “The Shear Strength of Reinforced Concrete Members.” ASCE Journal,
Structural Division (June 1973).