Bar bending formulas

There are several bar bending formulas used in the construction industry to calculate the length, shape, and size of steel reinforcing bars (rebars) for concrete structures. Here is a list of some of the most common bar bending formulas:

Bar Length Formula: 

L = D * π + 2 * C + ((N - 2) * S) 

Where: 

L = Length of the bar 

D = Diameter of the bar π = 3.14 (pi) 

C = Bend allowance (usually taken as 1.5 times the diameter of the bar)

 

N = Number of bends in the bar S = Distance between bends (center to center)

Bend Deduction Formula: 

BD = (2 * A - π * R) * (π / 180) 

Where: 

BD = Bend Deduction 

A = Angle of bend 

R = Radius of bend

Development Length Formula: Ld = (Db * Fs * Fy) / (4 * Fsu * φ) 

Where: 

Ld = Development length 

Db = Diameter of the bar 

Fs = Stress in the steel

 

Fy = Yield strength of the steel 

Fsu = Ultimate tensile strength of the steel 

φ = Factor of safety (usually taken as 0.7)

Stirrup Length Formula: L = (2 * Lb * N) + (π * D * N) + (4 * Lh * (N - 1))

 

Where:

 

L = Length of the stirrup 

Lb = Length of the bend 

N = Number of bends

 

D = Diameter of the bar 

Lh = Length of the hook

Cutting Length Formula: Lc = L - (2 * C) + (K * (Db/2))

 

Where: 

Lc = Cutting length 

L = Length of the bar 

C = Clear cover 

K = Constant (usually taken as 1.57 for 90-degree hooks) 

Db = Diameter of the bar

Crank Length Formula: Lc = 2 * L + (2 * C) + (K * (Db/2)) 

Where: 

Lc = Crank length

 

L = Length of the crank

 

C = Clear cover

 

K = Constant (usually taken as 1.57 for 90-degree hooks)

 

Db = Diameter of the bar

Shear Reinforcement Formula: Asv = (0.4 * Fy * Av * cot θ) / (Fu - 0.4 * Fy) 

Where: 

Asv = Area of shear reinforcement 

Fy = Yield strength of the steel

 

Fu = Ultimate tensile strength of the steel 

Av = Area of the concrete section under consideration 

θ = Angle of inclination of the inclined reinforcement

These are just a few examples of bar bending formulas used in construction. It's important to note that different formulas may be used for different situations, and it's important to consult with an experienced engineer or construction professional before using any of these formulas in a real-world scenario.