Rebar Development & Lap Calculator, ACI 318-19

What it checks

The module designs the development length of a deformed bar in tension, its standard hook, and the tension lap splice. It applies the strength-based provisions of ACI 318-19, specifically sections 25.4 and 25.5. The calculation sequence begins by determining the basic development length using either the tabulated values or the general equation, then evaluates the standard hook length, and finally determines the required lap splice length and classification.

Inputs

Bar Properties - Bar size (No. 3 to No. 11), lightweight concrete flag, and epoxy-coated or zinc and epoxy dual-coated flag.
Placement Conditions - Top bar flag for more than 12 in of fresh concrete below, clear cover to the bar (in), and clear spacing between bars (in).
Confinement - Minimum ties flag, transverse bar area across the splitting plane (in²), centre-to-centre spacing of transverse bars (in), and number of bars along the splitting plane.
Method Selection - Flag to use the general equation instead of the table, and hook spacing (in) for hooked bars.
Hook Details - Confining ties flag, side cover normal to the hook plane (in), and flag for hooks terminating inside a column core.
Lap Splice - Ratio of provided to required area and percent of area spliced within the required lap length.

What it reports

Effective Concrete Strength - The square root of f'c as used, capped at 100 psi.
Applicable Table Row - The specific row from Table 25.4.2.3 that applies, identified as "spacing and cover" or "other cases".
Confinement Ratio - The value of (cb + Ktr)/db as used, limited to a maximum of 2.5.
Development Length - The final ld used, which is the chosen method result but never less than 12 in.
Splice Class - The classification as "A" or "B" based on the area ratio and percent spliced.

Code references

The engine cites ACI 318-19 §25.4.2 (ld, Table 25.4.2.3 / Eq. 25.4.2.4a), §25.4.3 (ldh), and §25.5.2 (lap). It also references §25.4.1.4 for the square root limit, §25.4.2.1 for the minimum length, Table 25.4.2.5 for the psi factor cap, and Table 25.5.2.1 for splice classes.

Limits

The module does not tabulate bar sizes No. 18 and No. 14. It assumes the square root of f'c is capped at 100 psi and that the development length never falls below 12 in. Results are engineering aids; the engineer of record is responsible for the design.

This module ships in the desktop app

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