What Is Development Length for Rebar per ACI 318?
Development (the 25's — the chapter's; the bond's) is the rebar's (the embedded — the length; the ld) needed to develop (the fy's — the yield; the 60 ksi). The length: the ld (the 12-80db's — the computed; the 25.4's), the factors' (the psi_t's — the top's; the psi_e's — the epoxy's; the lambda's), and the hooks' (the ldh's — the 90°'s; the 12db's). The bar's — the developed yield.
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The ld equation
The 25.4.2 (the ld's — the 3/40*fy/(lambda*sqrt(f'c))*db; the simplified), the 12-inch (the minimum's — the 12's; the db's — the 12db's), the 80db (the max's — the #11's; the computed's), the psi_t (the 1.3's — the top's; the 12-inch's — the below), the psi_e (the 1.2's — the epoxy's; the 1.5's — the combined), and the 2.5 (the cb+Ktr/db's — the 2.5's; the cap's).
Hooks and splices
The ldh (the 90°'s — the 12db's; the 6-inch's — the minimum), the 180° (the 4db's — the tail's; the J's), the Class B (the 1.3ld's — the splice's; the 100%'s — the spliced), the Class A (the 1.0ld's — the 50%'s; the staggered), the mechanical (the 1.25fy's — the Type 2's; the 125%'s), and the 6-foot (the stagger's — the 24-inch's; the 600db's).
Details
The 3-inch (the cover's — the 2's; the 25.4's), the 2db (the spacing's — the 1's; the 25.2's), the bundled (the 3-4's — the 1.2x's; the ld's), the 60 ksi (the fy's — the 80's; the 1.33x's), and the epoxy (the 1.2's — the coated; the 1.5's — the top's). The development's — the bond's length; the 25's chapter.
The bottom line
Compute ld per ACI 318 25.4 (3/40·fy/(λ√f'c)·db with ψt 1.3 top / ψe 1.2 epoxy, cap (cb+Ktr)/db at 2.5; min 12 in) — use 90° hooks (ldh) where space is tight, Class B splices (1.3ld) at 100%, Type 2 mechanical for 125% fy.
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