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.
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.
Switching to Eurocode replaces the AASHTO factor chain with the EN 1992-1-1 bond model: the design bond stress comes from the 5 % tensile strength (capped at C60/75) divided by γc 1.5, the steel works at fyk/1.15, and the required length is then trimmed by the cover, link and shape coefficients of Table 8.2, never below the minimum lengths. KDS uses the Korean concrete bridge code KDS 24 14 21 (4.5.4 and 4.5.5), which keeps the same structure but works with material factors as multipliers: bond strength is 0.65 × 2.25η1η2fctk with fctk taken from the mean strength fck + 4 to 6 MPa and capped at 3.07 MPa, the bar works at 0.90fy, and the minimum lengths use 15 bar diameters. Under both codes the bond-condition toggle becomes good or poor bond, the spiral toggle sets the link-corner factor K, and the excess-steel slider scales the bar stress. Laps grow with the share of bars spliced at one section through α6, so set the new ρ1 slider to match the drawing. Coated and lightweight bars have no direct equivalent in these clauses and are hidden; the KDS hook-tie bonus (α6 of Table 4.5-4) is not taken.