WHAT IS BAR BENDING SCHEDULE?

BBS stands for the bar bending schedule. In this process, the bending of reinforcing steel into different shapes required for RCC constructions was noted. This operation is commonly done at the site. In bar bending schedules the cut, bend, bundled and the location of bars are readily determined.

BBS is a list of the reinforcing bars and is represented in a tabular form. This tabular form summarizes all the particulars needed of bars, its diameter, its shape of bending, length and its length of each bent, bending angles, the total length of each bar and the number of every type of bar.

The process of making the list of the type of bar, its location, size, length, mark and bending and all other given details is called scheduling. The (IS: 5525) shows the different recommendations and also make the standard length in the bar length calculation works. The length tolerance is +- 25mm.

Bar bending schedule is used as a frame of reference by the steel fixers and then the steel fixers can easily make of the number and kind of reinforcing bars for a structural construction.

Importance of BBS

• It is very important in any RCC construction.
• The preparation of BBS helps us to determine the steel quantity, its strength and cost estimation.
• Easy to make the billing of the construction work.
• We know the weight of the bar of different sizes required for the RCC work.
• The bar bending schedule gives a clear idea about the cutting length, dimension and number of reinforcing rebars.
• Bar bending schedule leads to the estimation of the total quantity of steel.

How to prepare a BBS

Ever BBS should have the following necessary details.

1. Bar size/bar mark reference
2. Shape of bar
3. Diameter of bar
4. Spacing of bars
5. Length of bar
6. Cutting length of bars

Bar bending schedule of column (step by step)

Step1:

First, we calculate the total length of the vertical bar.

Formula:

• Total length of vertical bar = floor height (1,2,3) + height of ground level + L_d + overlap length .

Step2:

In this step, we calculate the lapping length.

1. We know that each bar is 12 meter or 40 meters in length in some cases. we also know that the lapping length is generally taken 50d. which means 50 multiply by the diameter of the bar.

Step3:

After this, we calculate the cutting length of the stirrup.

Formula:

• Cutting length of stirrup = stirrup perimeter + bends + hooks.
• Note: for 90 deg bend minus 2d, and for 135 deg bend we minus 3d.

Step4:

Then we calculate the total number of stirrups.

Formula:

• No of stirrups = Total length / spacing of bar + 1.

Step5:

In this step, we calculate the weight of total bars.

Formula:      

• weight = D² / 162  x total length of bar

Step6:

After all, we prepare the bar bending schedule and add the total results we have above calculated.

Advantages of bar bending schedule:

1. It provides us the correct and better estimation of reinforcement for each structural member which can be used to determine the required reinforcement.
2. Using the bar bending schedule, it saves us 5 to 10% quantity of steel.
3. It also reduces our construction time and the wastage of steel and cost of steel due to the less requirement of workers for bar bending.
4. Increases the faster execution at the site.
5. BBS can be used for the reinforcement cutting, bending of the structural member before it can be installed at the required position.
6. Bar bending schedule improves the accuracy of bar cutting and bending.

Percentage of reinforcement according to concrete:

BBS member                        % According to the volume of concrete

Column                                                          2.5
Beam                                                               2
Slab                                                                 1
Footing                                                          0.8

Every structural engineer should know that the bar bending schedule for the different structural member such as,

• Steel calculation for columns
• BBS for beams
• BBS for slab

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