ACI 318-19 Development Lengths
Basic straight tension development length is calculated using equation 25.4.2.3. The following factors are used in this equation:
Ψg = reinforcement grade factor
- 1.0 for fy ≤ 60 ksi
- 1.15 for fy = 80 ksi
- 1.3 for fy = 100 ksi
Interpolation used to calculate values for reinforcement grades between 60 ksi and 100 ksi.
c = cover dimension, vertical distance from the center of the bar to the nearest concrete surface (spacing is not considered)
The term (c + Ktr)/db is never taken greater than 2.5
Ktr is conservatively assumed to be zero
Sections 9.7.4.1 and 25.4.2.2 are not implemented.
Tension development length of standard hooks is calculated using equation 25.4.3.1. The following factors are used in this equation:
Ψc = concrete strength factor
- (f’c/15,0000 + 0.6) for f’c < 6000 psi
- 1.0 for f’c ≥ 6000 psi
The location factor (Ψo) is assumed to be 1.0.
When laying out program reinforcement, RAM Concept first attempts to detail reinforcement without confining reinforcement. The confinement reinforcement required for program or user reinforcement defined with "90 Hook (Confined)" or "180 Hook (Confined)" bar ends must by designed by the user outside RAM Concept .
In accordance with sections 7.7.3.3 and 9.7.3.3, the extension length used for this Code is the maximum of 12db or effective depth of the member, taken as the maximum vertical distance from the center of the reinforcing bar to the farthest concrete surface.
The minimum development length is 12 in for straight bars (25.4.2.1b) and 8db or 6 in for hooks (25.4.3.1b and c).