The Basics of Bar Bending Schedule (BBS)
The word BBS Plays a noteworthy job in any development of High ascent structures. BBS alludes to Bar Bending Schedule. Bar is any sort of rebar which is utilized as a reinforcement in RCC. The bar might be a Mild Steel bar or HYSD bar or TMT Bar.
Bar Bending Schedule is named as "Estimation of the all-out Steel required for the development of a structure" We use steel to make concrete to be strengthened and for pressure prerequisites. In any case, what amount steel required for developing 15 stories building? The amount Steel we need to arrange? Every one of these inquiries are replied in BBS.
In Bar bending schedule, the bars are sorted out for each basic units (Beams or sections or pieces or footings and so forth) and definite rundown is readied which determines the Bar area (Bar in footings, chunks, bars or segments), Bar Marking (to recognize the bar as per the drawing), Bar Size (length of the bar utilized), Quantity (No. of Bars utilized), Cutting length, Type of Bend and Shape of the bar in reinforcement drawings.
Prior to managing the BBS, it's essential to get familiar with the nuts and bolts of Bar bending schedule.
The beneath referenced table is a launch control for taking in Bar bending schedule without any preparation. Beneath we are talking about the various ideas of Bar Bending schedule which are valuable while working with BBS. Every one of these ideas are utilized in BBS plan figuring of any auxiliary part. So be acquainted with the underneath ideas. To keep it clear, right off the bat the ideas are examined and at long last, this post is shut with a case of BBS count of a part.
Hook Length or Cutting length of Stirrups
The hook length is usually given to stirrups in shafts and ties in sections. When all is said in done, Hooks are included at the two finishes of the rebar in stirrups or ties.
Hook Length = 9d (d is dia of the bar)
Length of hook = [(Curved Portion) + 4d] = [(4d+d)+4d] = 9d
Hook Length = 9d [d is Diameter of the Bar]
Complete Cutting Length of stirrup or tie = Total length of Bar + 2 x Hook Length (Two hooks)
Complete Cutting Length = L+2(9d)
In this way Total Cutting length = L+18d (d is the Diameter of a bar)
The Bend length computation is distinctive for Cranked bars (bent up bars) and bends at corners. The bars are typically turned in Slabs and bars are bent at corners in Stirrups or ties.
(I) Bend Length estimation in Cranked Bars:
As Shear pressure is most extreme at underpins in Slab. To oppose these burdens, we generally wrench the bars at the closures of supports in the piece.
The bar is bent at an edge θ0 the extra length (la) is presented.
Where, la = l1 – l2–(I)
Tanθ = D/l2 ; Sinθ = D/l1
Henceforth l1 = D/Sinθ and l2 = D/tanθ
In this way from (I) :- la = D/Sinθ – D/tanθ
Model Calculation thinking about Bent up bar in Slab (Cranked bar):
To keep the wrench bar in position, an additional bar of length (L/4) is given beneath the wrench bar as appeared in the underneath figure. Consequently, the absolute length of bar = L+0.42D+0.42D+(L/4)+(L/4) = 1.5L+0.84D
Recollect D = Depth of Slab-Top Cover-Bottom spread
(ii) Bend Length estimation when bars are bent at corners:
The significant principles utilized while computing the bend length at corners
45° Bend length = 1d
90° Bend length = 2d
135° Bend length = 3d
Here, 'd' = Diameter of bar
Model Calculation thinking about stirrup with the bends at corners:
There are 3 bends which are bent at a point of 900 and two bends are bent at an edge of 1350
All out bend length = 3 x 900 Bend length + 2 x 1350 Bend length = 3 x 2d + 2 x 3d = 12d = 12 x 8 = 96mm
Cover Length/Lap Length in Reinforcement
The standard length of Rebar is 12m. Assume the tallness of the segment is 20 m. To furnish this necessity, two bars of length 12m and 8m are covered (gotten) with cover length.
Cover Length for pressure individuals (segments) = 50d
The Overlap Length for strain individuals (bars) = 40d
[d is the Diameter of the bar]
BBS of Column
Auxiliary Member - Column
Bar Marking 1. Principle Bars 2. Stirrups (Longitudinal bars)
Dia of Bar 1. Principle Bars = 16mm ; 2. Stirrups
(Longitudinal bars) = 8mm
No. of Bars used 1. Principle bars = 4 2. Stirrups = 30
Cutting length 1. Principle bars = 3.16m 2. Stirrups = 2.64m
All out Length of bar 1. Primary bars = 18.4m 2. Stirrups = 43.2m
Weight of Steel bar 1. Principle bars = 29Kgs 2. Stirrups =17Kgs
All out weight of steel bar required to do BBS of above segment = 46Kgs
Focuses to review
1. The bars utilized in building ought to be gathered for each basic unit and recorded seperately for each floor.
2. Bars are recorded in numerical request.
3. To distinguish the bar in the heap of bars, each bar is interestingly marked with reference subtleties (Length of the bar, size of the bar, Shape of the bar)
4. The kind of bar and state of the bar ought to be as per B8666.
5. It is fundamental that the bar mark reference on the name connected to a heap of bars alludes interestingly to a specific gathering or set of bars of characterized length, size, shape and type utilized at work.
6. The cutting length and bending length computations are independently determined and excluded from the point by point list. Like I have recorded the Bar Bending subtleties in a table and counts are done independently.
7. BBS assists with assessing the all-out amount of steel required for the development of building or structure. It assists with citing for delicate the expense acquired by steel.
8. Finding the cutting length and bending length in reinforcement enumerating improves the nature of development and limit the wastage of steel, makes a financial development
9. With the assistance of reinforcement drawings, cutting and bending should be possible at the industrial facility and shipped to the site. This increments quicker development and diminishes the complete development cost.
10. For site engineers, it turns out to be anything but difficult to confirm the cutting length and bending length of the reinforcement before setting the concrete.