Standard reinforcing bar hook development details specify standard bend diameters and minimum extension lengths for 180-degree, 135-degree, and 90-degree hooks based on bar size. The 180-degree hook requires a bend diameter D with an extension of four bar diameters or two and a half inches minimum. The 135-degree hook requires a bend diameter D with an extension of six bar diameters or two and a half inches minimum. The 90-degree hook requires a bend diameter D with an extension of six bar diameters or two and a half inches minimum for bars less than or equal to size number five, and twelve bar diameters for bars greater than or equal to size number six.
1" 90 DEGREE 12" 6" db D 4db, OR 2 1/2" MIN db 180 DEGREE 6" db D 4db, OR 2 1/2" MIN 8" db 135 DEGREE 6" db D 6db, OR 2 1/2" MIN ≤#5 BAR: 6db OR 2 1/2" MIN ≥#6 BAR: 12db HOOK DEVELOPMENT
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