Shrinkage and Temperature Reinforcement (ACI 318-19 24.4)
Minimum shrinkage/temperature steel perpendicular to the main bars in a one-way slab.
Example
You enter
- Slab thickness h (in) 6
- Design strip width b (in, default 12) 12
- Reinforcement grade (ksi) 60
You get
- Reinforcement ratio 0.0018
- Minimum area As,min = ratio x b x h 0.130 in^2 per strip
- S max (in) 18
Checked against published worked examples from: StructurePoint.
Details, formula, and sources
ScopeRatio 0.0018 for deformed bars of any grade (ACI 318-19; the 0.0020 for Grade 40/50 was the 2014 edition), As,min = ratio x b x h, spacing <= min(5h, 18 in). A 6 in slab, Grade 60 -> 0.130 in^2/ft, 18 in max (about #4 at 18). A design aid; the engineer of record's stamped design governs.
Formula or tableratio = 0.0018 for every bar grade (ACI 318-19 Table 24.4.3.2); As,min = ratio x b x h; s_max = min(5h, 18 in).
Source and editionThe ACI 318-19 24.4 shrinkage and temperature reinforcement provisions, by name.
Free accessACI 318 is readable free through the ACI online reading room at concrete.org; the 24.4 shrinkage-and-temperature provisions are in the published code.
What governsEstimate. AHJ and licensed professional govern.
API field namesh_in, b_in, grade_ksi, ratio, as_min_in2, s_max_in
- Minimum ratio 0.0018, all gradesACI 318-19 Table 24.4.3.2
- Minimum area As,min = ratio x b x h per stripACI 318-19 24.4.3.2
- Spacing limit s_max = min(5h, 18 in)ACI 318-19 24.4.3.3