CIVIL ENGINEERING DEPARTMENT

Sem-6^th

SUBJECT- LAND SURVEY-II

AIM OF THE EXPERIMENT- Setting out a simple curve by offsets from chords produce

By

MR.BIKASH KUMAR DAS

(LAB. ASST. IN CIVIL ENGG. DEPT.)

AY:2021-2022

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Bar Bending Schedule ( BBS )-

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• Bar Bending Schedule provides details of reinforcement cutting length, type of bends and bend length. It is Systematic tabular form or Simple form which provides the details like shape of the bar , dimension of bending of the bar etc.
• Bar bending schedule makes it easy for site engineers to check and verify the cutting length and bar bending while inspection on the site. At the end of the entire work the construction bills can be easily created with the help of these schedules of bars.
• Bar bending schedule or schedule of bars is a tabular representation of reinforcement bar. It is generally represented for each type of R.C.C work.
• With the help of bar bending schedule the requirement of different length and sizes of bars may be known and can be arranged and bent-up during the time of construction.
• Bar bending schedule generally describes the particulars of bars, shape of bending with sketches and total length and weight of the bars along with their numbers.
• Bar bending schedule is generally prepared while estimating a R.C.C work or structure.

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Advantages of BBS-

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• Quantities of steel reinforcement of different diameter and different grades are calculated easily.
• Ideas of different sizes of bars, bend and length of bars can be easily acquired through schedule of bars.
• During the auditing of reinforcement on construction site, bar bending schedule becomes very much helpful.
• Moreover it helps to avoid confusion on the construction site.
• It provides the exact quantity of steel required for work due to which optimization of reinforcement can be done in case of cost overrun.
• Bar bending schedule makes it easy for site engineers to check and verify the cutting length and bar bending while inspection on the site.
• At the end of the entire work the construction bills can be easily created with the help of these schedules of bar.

BBS provides the reinforcement calculation for reinforced concrete beam

• Curtailment is a theoretical point where some of the reinforcement is cut-off along the span of the beam where the bending moment reduces, given that the remaining reinforcement will be able to support the reduced bending moment.
• The extra bar provided with main bar of bottom reinforcement in the center of the beam to resist Bending moment.

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HOOK LENGTH:

• The hook is the extra length left at the 4th corner of a stirrup so that the stirrup retains its shape.
• We generally consider length of hook = 10 D (for bars having diameter greater than or equals to 8 mm)

• d = Diameter of stirrup
• Is code recommends,
• Minimum hook length = 75mm
• Deduction for Elongation
• 135 Degree – 3d
• 90 degree = 2 d
• 45 Degree – 1d
• The total length of stirrups = Total length of the bar + 2 x hook length (for two hooks)

= L + 2 x 10 d -Deduction

= L + 20 d – Deduction

Where L = length of the bar for stirrup

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• DEVELOPMENT LENGTH:

The development length can be characterized as the length of the bar required for transferring the stress into the concrete. The development length Ld of a bar is calculated as following

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Where d = diameter of the bar.

σs = stress in the bar at the section considered as design load.

τbd = Design bond stress.

LAP LENGTH:

 Lap length is one of the important term in the reinforcement. This is usually confused with another important term called development length and anchorage length.

Lapping can be defined as the overlapping of two bars side by side to up to the design length .

Lap length for tension members = 40 d

Lap length for compression members = 50 d.

where, d = Diameter of bars.

CRANK LENGTH:

Bars are bent near the support at an angle of 45°. The angle of bend may also be 30° in shallow beams. The purpose of bend near the support is firstly to resist the negative bending moment which occurs in the region of the support and secondly to resist the shear force which is greater at the support.

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• Crank bars are mostly provided in beams and slabs :-

Formula for calculation of Crank Length = 0.42 D

Where D = Clear height of the bar = Thickness of slab – (Top cover + Bottom cover) – Diameter of the bar.

• Standard Hook (180° Bend) :

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• Extra length for 1 hook = 9Φ
• Extra length for 2 hooks = 2 × 9Φ = 18Φ

For 90° Bend :

• 90° bend is generally provided for HYSD (High Yielding Strength Deformed) Bars.
• Extra Length for one 90° bend = 6Φ
• Extra length for two 90° bend = 2 × 6Φ = 12Φ

Bent-up Bars 

Extra length for one bent-up = \frac{d}{sin45}-d=0.42d

Extra length for two bent-up bars = 2 × 0.42 d = 0.84 d

d = D – (top cover + bottom cover)

 For Two Legged Stirrups :

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• Extra length of hook = 24Φ
• A = b – 2 (side cover)
• B = D – (top cover + bottom cover)
• Total length of stirrups = 2 (A + B) + 24Φ         …… (Φ = dia of steel reinforcement)

Calculate Weight of Bars in Bar Bending Schedule :

Weight of bars is generally calculated in Kilograms and it is calculated for every one meter length.

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Weight of Bars in Kg/m = \frac{\phi ^{2}}{162}

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Here, Φ = diameter of bars used.

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#Calculation of Number of Bars :

Number of Bars = \frac{span}{spacing}+1