Straight tension development with the full factor chain (λrl · λcf · λrc · λer)/λ, plus compression development, standard hooks, and Class A / B tension laps — converted exactly from the ksi-inch code equations to SI.
Top bar = more than 300 mm of fresh concrete cast below (λrl = 1.3). Epoxy factor is 1.5 when cover < 3db or clear spacing < 6db, else 1.2; the product λrlλcf is capped at 1.7.
Ktr = 40Atr/(s·n) and λrc = db/(cb+Ktr), bounded 0.4–1.0. The spiral toggle applies the 0.75 factor to compression development only.
| Basic ℓdb = 0.914 dbfy/√f′c | – |
| λrl location | – |
| λcf coating | – |
| λrc confinement (cb=–, Ktr=–) | – |
| λer excess reinforcement | – |
| λ concrete density (divisor) | – |
The confinement factor is where drawings win or lose constructability: with generous cover and spacing λrc bottoms out at 0.4 and a 420/35 bar develops in about 29 diameters, but a congested face with minimum cover pushes the same bar toward the full basic length — three times longer. Two habits from checking shop drawings: call the splice Class B unless you can actually demonstrate the Class A conditions (staggered laps and twice the required steel — rarer than people assume), and remember the epoxy and top-bar factors stack until the 1.7 cap, which is routinely what governs top mats of decks. Hooked bars are the escape hatch at joints, but the hook length here assumes the side-cover conditions of a typical member interior — thin edges need the tail checked separately. Values are exact SI conversions of the ksi-inch equations, rounded up to 5 mm for the schedule.