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Basic concepts in bar bending scheduling and structural engineering | reinforcement detailing
Bar bending scheduling is an important task in the process of building construction. In this article you will able to learn about some important basic concepts considered in the bar bending scheduling BBS and structural engineering. While analyzing and designing the structural components we have to remember these some important
Important bar bending scheduling basic points
The basic important concepts of bar bending scheduling are listed below
- Diameter of reinforced bars
- Hooks
- Overlapping of bars
- Crank bars
- Concrete cover
- Spacing of reinforcement
- Number of bars
- Number of stirrups
The detailed concepts of BBS are given below
1. Diameter of reinforced bars in bar bending scheduling
In general the reinforcement bars are available in the market like 8mm, 10mm, 12mm, 16mm, 20mm, 24mm, 30mm, 36mm, 40mm etc. The diameter of the bar depends upon the loading condition and grade of the concrete. If the loading on the structure or grade of the concrete increases then we have to increase the diameter of the steel bars. Based on the requirement in the structural design we will use the diameter of the bar.
The customized sizes also available in the industry we can order the customized sizes before construction. But this customized bar sizes will not be available in the market because of the rare use in the construction industry.
2. Calculation of weight of the bars
The weight of the reinforced bar is calculated by using the below expression in kilograms. Here the weight of the bar depends upon the diameter of the bar and length of the bar. If the diameter of the bar is increases then the weight of the bar is also increases, in the same process if the length of the bar increases then the weight of the bar increases. The standard length of 40 feet which is approximately equal to 12m.
Weight = (D2/162)XL
Standard length of bar = 12m (40 Feet)
3. Hooks
Hooks will gives grip to the main reinforcement bars in BBS. If the hooks are not provided in the structural members then the main bar will slip out ward because of this reason there will be a chance of observing the cracks in the beams, columns or slabs etc.
Main uses of the hooks in the structural design are discussed below
- Used to prevent seismic moment
- Prevent concrete from splitting outward
- To keep the longitudinal bars in position
- Used to develop anchorage length
The length of the only hook is calculated by using the below equation
Hook length = 9d
The cutting length of the hook is determined by using the below equation
Cutting length = L+9d+9d
4. Bends in bar bending scheduling
The bends are usually provided in the footings at each corner end of the reinforced steel bar. The values of the bend length and the cutting lengths of the beds are determined using below specified equations
Bend length = 10d to 16d (Generally 12d)
Cutting length = L+12d+12d
5. Overlapping length
The overlapping is the process of joining the two or more bars to make a single bar as per the required lengths in the structural components. The joining process of the reinforced bar is done with the binding wire. In generally the length of the reinforced bar is 12m which is approximately 40 feet in length if the column or beam or slab is greater than 40 feet we use overlapping length of the bars.
The values of overlap lengths for columns, beams and footings are calculated by using below specified expressions
- For compression member (Columns) overlapping length = 40d
- For tension member (Beams) overlapping length = 50d
- For neck columns to footings = 16d
6. Crank bars in bar bending scheduling
In general the slab member is takes sagging and hogging bending moments. The more damages in the slab members are obtained due to the effect of the hogging bending moments we can call this moment as hogging bending moment. The main purpose of the crank bars are to prevent the negative bending moment (Hogging bending moment) in the slabs.
The values of the crank lengths and cutting lengths for the steel bar is determined using the below equations
Crank length = 0.42d
Cutting length = L+0.42d+0.42d
7. Concrete cover
The cover is the distance between the edge of the beam or column to the side of the reinforcing bar. In other words cover is the spacing between the reinforcing bar and outer surface. Generally cover is provided to prevent the steel from corrosion. The concrete cover is provided in all the structural elements to give proper strength values. The minimum cover is provided in the beams as per IS 456 code is 25mm.
The below specified values shows the concrete cover values for some structural components
- Minimum cover = 50mm
- Columns and beams = 25mm to 50mm
- Slabs = 20mm
In general cover is taken as 10% the higher dimensions of the structural member
spacing of the reinforcement
The spacing in the reinforcement will be given to provide proper dimensions of the structural elements from the ground level to the top level in the building. It is the distance between the two reinforced bars. It is generally provided to give proper anchorage.
Minimum spacing = maximum size of aggregates + 5mm
8. Number of the bars
The number of the bars required for the slab is calculated by using below formulas
Number of bars = (Opposite length/Spacing)+1
Number of bars on X direction = (Length in Y direction/Spacing)+1
Number of bars on Y direction = (Length in X direction/Spacing)+1
9. Number of the stirrups
The number of the stirrups required for the structural members are calculated by using below formulas
Number of stirrups= (Actual length/Spacing)+1
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Conclusions of Basic concepts in bar bending scheduling and structural engineering
Well now the above explained concepts are related to the complete basic concepts of bar bending scheduling and structural engineering. Which are used mainly in the site executions related to diameter of reinforced bars, hooks, overlapping of bars, crank bars, concrete cover, spacing of reinforcement, number of bars and number of stirrups.
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