Precast Plank + Topping Calculator

Two-stage design: bare plank during construction vs manufacturer table, and composite ultimate flexure per ACI 318-19 / DPT 1008-61

ACI 318-19DPT 1008-61Two-Stage DesignEvidence-Gated

Note: This tool calculates per ACI/DPT standards but does not replace review by the design engineer.

Simple span (m)

Plank width (m)

Common standard is 0.35 m

Plank thickness t_p (mm)

Topping thickness t_t (mm)

Topping fc' (MPa)

From the manufacturer's wire certificate (TIS 95) — these are money numbers, never guess

Wires per plank

Wire diameter (mm)

fpu (MPa)

Ultimate tensile strength from the wire certificate — no default

fpy/fpu ratio

Selects γp per ACI 318-19 Table 20.3.2.4.1

Wire centroid from bottom (mm)

Mid-plank wires = t_p/2 = 25 mm

Service (unfactored) loads — plank+topping self weight is computed automatically

Superimposed dead load (kPa)

Finishes, partitions, MEP

Live load (kPa)

Design Code

Checks the bare plank during topping pour against the manufacturer table (service level)

Check Stage 1 construction case

Shoring during pour

Sets the effective span Ls = L, L/2 or L/3

Construction live load (kPa)

Required — workers, tools, wet concrete heaps

Allowable moment per plank (kN·m)

From the manufacturer table (service level) — never guess

Manufacturer table source (evidence)

Required — money numbers need evidence, e.g. CPAC plank table 5 cm, 2025

Ready to calculate

Fill in the form and calculate to see Stage 1 + Stage 2 results