Checks for limiting parameters (pad and strip base: ACI 318)
Limiting reinforcement parameters are specified in Design Settings > Concrete> Cast-in-place > Foundations > Isolated Foundations > Reinforcement Layout
Limits on bar size and reinforcement quantities
For structural foundations of uniform thickness the minimum area of tensile reinforcement shall be:
For metric units:
IF Grade 280 to 350 deformed bars are used
As,min,reqd ≥ b * h * 0.0020
IF Grade 350 to 420 deformed bars or welted wire reinforcement are used
As,min,reqd ≥ b * h * 0.0018
IF yield stress exceeds 420 MPa
As,min,reqd ≥ b * h * [MAX(0.0014 , 0.0018*420/fy)]
For US-units:
IF Grade 40 to 50 deformed bars are used
As,min,reqd ≥ b * h * 0.0020
IF Grade 50 to 60 deformed bars or welted wire reinforcement are used
As,min,reqd ≥ b * h * 0.0018
IF yield stress exceeds 60000 psi
As,min,reqd ≥ b * h * [MAX(0.0014 , 0.0018*60000/fy)]
where
b = unit width
The maximum area of tensile reinforcement is:
As,max ≤ 0.85 * (f`c/fy) * β1 * b * d * (3/7)
where
Ag = the gross area of the concrete section
V = stress block depth factor1
For metric units:
| β1 | = | 0.85 | for f`c ≤ 28Mpa |
| = | 0.85 – 0.05 *[(f'c – 28MPa)/7MPa] | for 28MPa < f`c < 55Mpa | |
| = | 0.65 | for f`c ≥ 55MPa | |
|
For US-units:
| β1 | = | min(max(0.85 - 0.05 ´ (f'c - 4 ksi) / 1ksi, 0.65), 0.85) | |
| = | 0.85 | for f`c ≤ 4000 psi | |
| = | 0.85 – 0.05 *[(f'c – 4ksi)/1ksi] | for 4000 psi < f`c < 8000psi | |
| = | 0.65 | for f`c ≥ 8000 psi | |
|
|||
Footnotes
1 ACI 318-08, ACI 318-11, ACI 318M-08 and ACI 318M-11
Section 10.2.7.3