Crank Bar Calculator for Bent Up Bar Cutting Length
Calculate crank bar or bent-up bar cutting length with crank height, crank angle, extra length, hook length, lap length, bend deduction, steel weight and cost.
Slab और beam में bent-up/crank bar की cutting length निकालें। Crank height, angle, bar diameter और number of bars डालकर BBS-ready result प्राप्त करें।
Formula Preview
Extra Length = H × (cosecθ - cotθ)
45° Crank Example
Crank height = 150 mm
Extra = 0.42 × 150 = 63 mm
What is Crank Bar?
A crank bar or bent-up bar is a reinforcement bar bent upward or downward in slab or beam reinforcement. The crank creates an inclined portion, so extra length is added in cutting length.
Hindi Explanation
Crank bar में reinforcement bar को ऊपर या नीचे bend किया जाता है। इस bend की वजह से inclined length बनती है, इसलिए final cutting length में extra length add होती है।
Where to Use?
Use it for slab bent-up bars, beam crank bars, negative reinforcement, support zone bars, BBS checking and site bar cutting work.
Crank Bar Formula
Crank bar cutting length depends on straight length, crank height, crank angle, number of cranks, hook length, lap length and bend deduction. For a 45° crank, many site BBS calculations use the practical extra length factor 0.42H.
Crank Extra Length
Extra Length per Crank = H × (cosecθ - cotθ)
General crank bar formula where H is crank height and θ is crank angle.
45° Crank Approximation
Extra Length per Crank ≈ 0.42H
Common practical BBS formula for 45° crank bars.
Inclined Length
Inclined Length = H / sinθ
Used to calculate the inclined portion of the bent-up bar.
Horizontal Projection
Horizontal Projection = H / tanθ
Used to compare inclined portion with horizontal bar projection.
Crank Bar Cutting Length
Cutting Length = Straight Length + Crank Extra Length + Hook Length + Lap Length - Bend Deduction
Final cutting length formula for crank bars in BBS.
Steel Weight
Steel Weight = D² / 162 × Total Length in meter
Used to calculate total steel weight after crank bar cutting length is known.
Example Crank Bar Calculation
Given Data
Straight length = 3000 mm
Crank height, H = 150 mm
Crank angle = 45°
Number of cranks = 2
Bar diameter = 12 mm
Number of bars = 10
Calculation
Extra length per crank = 0.42 × 150
Extra length per crank = 63 mm
Total crank extra length = 63 × 2 = 126 mm
Cutting length per bar = 3000 + 126
Cutting length per bar = 3126 mm
Total length = 3126 × 10 = 31.26 m
Inputs Required
Output You Get
Crank Bar in Slab and Beam BBS
In Bar Bending Schedule, crank bars are used where reinforcement needs to change level, especially near supports, negative moment zones or bent-up bar detailing. Correct crank extra length helps avoid short cutting and steel wastage.
Slab Bent-Up Bars
Slab bars may be cranked near supports or alternate positions depending on reinforcement detailing.
Beam Crank Bars
Beam crank bars are used where bars are bent-up according to shear or moment requirements.
BBS Checking
Crank length calculation helps verify bar mark quantity, cutting length, total length and steel weight in BBS.
Related Steel Calculators
Use these related tools for complete steel reinforcement and BBS calculation workflow.
Crank Bar Calculator FAQs
What is a crank bar?
A crank bar, also called a bent-up bar, is a reinforcement bar bent upward or downward to resist negative moment, shear or support zone reinforcement requirements.
What is the formula for crank bar extra length?
The general formula is Extra Length per Crank = H × (cosecθ - cotθ), where H is crank height and θ is crank angle.
What is the extra length for a 45° crank?
For a 45° crank, the common practical BBS formula is Extra Length per Crank = 0.42H.
Where is crank bar used?
Crank bars are commonly used in slabs, beams, bent-up bars, negative reinforcement zones and BBS cutting length calculations.
What is crank height?
Crank height is the vertical distance through which the bar is bent up or bent down. It can be calculated from slab thickness, clear cover and bar diameter.
Is bend deduction required in crank bar?
Yes, if the BBS method or drawing requires bend deduction, it should be subtracted from the crank bar cutting length.
Can lap length be added in crank bar cutting length?
Yes. If a crank bar has lap requirement, lap length is added to the final cutting length.
Can steel weight be calculated from crank bar length?
Yes. After total crank bar length is calculated, steel weight can be calculated using D²/162 × total length in meter.
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