Liquid-containing tank wall
A concrete wall of a rectangular or circular tank under the hydrostatic pressure of a full tank: the vertical moments and shear, the hoop tension of a circular wall, flexure and hoop steel with the environmental durability factor Sd, shear without stirrups, and the liquid-tightness detailing rules (minimum steel by the distance between movement joints, thickness, cover, spacing). ACI 350-20 is not readable on disk and the PCA tank tables are not on disk: the ACI 350 rules are written from knowledge of ACI 350-06 and marked "to confirm against the code text"; the walls are analysed in closed form.
Inputs of the tank wall #
- Materials: f'c and the bar grade.
- Tank: rectangular (a vertical strip per foot: cantilever from a fixed base, fixed base and pinned top, or pinned at both ends: your choice) or circular (fixed or free sliding base, inside radius, Poisson's ratio); liquid depth, wall height, liquid unit weight.
- Wall: thickness, cover, the vertical bars at the face in tension at the base and their spacing, the horizontal bars on each face, the exposure (normal or severe, yours) and the distance between movement joints.
Auto-design varies the thickness and the vertical and horizontal bar spacings; the bar sizes and the rest are kept.
Checks performed #
| Check | Basis |
|---|---|
| Service effects | Strip: γH³/6, γH³/15, γH³/(9√3) moments; cylinder: free base T = γHa, fixed base Timoshenko §117 (to confirm) |
| Vertical flexure | Sd Mu ≤ φMn, Mu = 1.4 Ms (ASCE 7-22 2.3.1), Sd = φ fy/(γ fs) ≥ 1, fs = 320 (260) / (β √(s² + 4(2 + db/2)²)) (ACI 350, to confirm) |
| Hoop tension (circular) | As ≥ Sd Tu/(φ fy), fs = 20 ksi (17 ksi severe) (to confirm) |
| Shear | Vu ≤ φ 2λ√f'c b d (ACI 318-19 22.5.5.1) |
| Minimum horizontal steel | ρ by the movement joint spacing (0.3 %, 0.4 %, 0.5 %) (to confirm) |
| Thickness, cover, spacing | 12 in. for walls 10 ft or taller, 2 in. cover, 12 in. spacing (to confirm) |
| Long shell (advisory) | βH ≥ 3 for the fixed-base cylinder solution |
The drawing is a wall section with the liquid level, the pressure and the bars.
Limitations #
- Full tank, hydrostatic only: the empty tank with backfill or groundwater, sloshing (ASCE 7-22 15.7.6), temperature, two-way action of rectangular walls and short circular walls (βH < 3) are not covered.
- Every ACI 350 value and the cylinder solution are from knowledge (to confirm against the code text).
Verification examples #
Verification status: 7 values compared in 5 examples (0 published, 5 hand calculations from the cited equations): 7 within tolerance, 0 recorded deviations. No published example: every value is a hand calculation. That checks the program against this reading of the code, not the reading itself. Code basis: written without the code document on hand, and confirmed only in part through published examples.
No published tank example is on disk. Hand calculations (closed form) check the three strip moments, fs and Sd, the hoop tension of a free-base cylinder and the base moment of a fixed-base long cylinder.