Tension Development & Splice ACI 318-99 §12.2 / §12.15
psi
psi
in
in
Compression & Standard Hook ACI 318-99 §12.3 / §12.5 / §12.16
Compression (uses bar & fy/f'c at left)
Standard Hook (tension)
in
in
Reference Table — All Bar Sizes current fy/f'c, 12" spacing, 2" cover, no ties
Ldt/Ldo = straight tension development (top/other). Lbt/Lbo = Class B splice (1.3×Ld). Ldh = standard hook development. Ldb = compression development. Methodology matches the public-domain "REBARS" (ACI 318-99) spreadsheet — verified to <0.01in on all bar sizes.
Ld = (3/40)×(fy·ψt·ψe·ψs·λ)/(√f'c·(cb+Ktr)/db)×db with ψt·ψe ≤ 1.7 and (cb+Ktr)/db ≤ 2.5; min 12in.
Class A = 1.0×Ld (needs As(prov)/As(req) ≥ 2 and ≤50% spliced within lap length); Class B = 1.3×Ld (safe default).
Hook: Ldh = (fy·ψe·ψr·ψo·λ)/(50√f'c)×db, min max(8db, 6in). Compression: Ldb = max(0.02fy·db/√f'c, 0.0003fy·db, 8in); splice = 0.0005fy·db (fy ≤ 60ksi), min 12in.