The stair is a component of the building which allow us to move from one floor to another floor. The place or area occupied by the stair is known as a staircase. Here I will show you how to calculate the Bar bending schedule of dog-legged staircase.
Bar bending of stair means simply to calculate the total quantity of steel rod or reinforcement required in the stair. The stair should be strong enough to bear the load of the people as well as goods as required.
There are different types of stairs you can read “Different types of stairs in civil engineering| types of stair in construction“. If you have already read then let’s move forward for calculation. Dog-legged stairs are those whose flight has turned 180 degrees with each other and landing is provided in the mid of the two flight.
Bar Bending Schedule of Dog-legged Staircase
For bar bending schedule of dog legged staircase you have to know some basic component of stair.
Staircase
The Space, where stairs are provided is called staircase.
Components of Staircase:-
Waist slab: The incline slab through which we go up and down from one floor to another is known as the waist slab. In a dog-legged stair, there is two waist slab.
Flight: The combination of steps between floor and landing is known as flight.
Landing : The intermediate point in the dog legged stair is known as landing.
Step: The combination of Riser and tread in the stair is known as step.
Tread: The tread is the horizontal portion of the step on which the foot is the place to go up and down the floor.
Riser: The riser is the vertical (up and down) part between each tread.
From Figure,
Given,
Height of floor = 3 meter
Height from floor to first landing = 1.5 meter
Width of landing = 2.5 meter
Clear Cover = 50 mm
Width of Waist Slab-1 = 1.2 meter
Width of Waist Slab-2 = 1.2 meter
Horizontal Length of Staircase = 3-meter Horizontal Length of waist slab = Length of staircase – Landing = 4.2 – 1.2
= 3 meter
Actual or Inclined length of waist slab of stair (H) = ?
Using Pythagoras theorem,
(H) = 3.354 meter
Now calculation of steel required,
For Waist Slab- 1,
![Bar Bending Schedule of Dog-legged Staircase - Step by Step]()
Step-1 Calculate Steel Rods in X-Direction
Cutting Length of one steel in X-Direction = Inclined length of waist slab + Length of Landing – Clear Cover of landing – Hook length at Plinth beam + Beam Cover Length – Bend Length
Here,
Inclined length of waist slab = 3.354 meter
Length of Landing = 1.2 meter
Clear Cover of landing = 0.05 meter
Hook length at Plinth beam = 9d = 9 x 12 = 108 mm = 0.108 meter
Beam Clear Cover = 0.01meter
Bend Length = 3d = 3 x 12 = 36 mm = 0.036 meter
Hence,
Cutting Length of one steel in X-Direction = 3.354 + 1.2 – 0.05 – 0.108 + 0.01 – 0.036 = 4.361 meter
No. of bars on waist slab in X-Direction
Number of the Main rod required = (Opposite Spacing)/Spacing of Srirrups + 1
Number of stirrups required = 1.10/0.1 + 1
{Since, Opposite width = Width of one stair – clear cover – clear cover}
Number of main rod required = 12 Nos.
Therefore,
Total Length of main rod in X direction = Length of one bar x Nos. = 4.361 x 12 = 52.33 meter.
Step-2 Calculate Steel Rods in Y-Direction
Cutting Length of one steel in Y-Direction = Width of stair + 2 x Development length
Here,
Width of Stair = 1.2 meter
Development length = 50d = 50 x 12 = 600 mm = 0.60 meter
Hence,
Cutting Length of one steel in Y-Direction = 1.2 meter+ 2 x 0.60 meter = 2.4 meter
No. of bars on waist slab in Y-Direction
Number of the Main rods required = Opposite Spacing/Spacing of stirrups + 1
Number of stirrups required = (3.35-2×0.5)/0.1 + 1
Number of main rod required = 33.5 Nos. Say 34 Nos.
Therefore,
Total Length of main rod in Y direction = Length of one bar x Nos. = 2.4 x 34 = 81.6 meter.
Step -3 Calculate weight of rods in X and Y Direction,
Weight of rods in X = W1 = (d2 / 162.25) x Length
W1 = (d2 / 162.25) x Length
W1 = (122/162.25) x 52.33
W1 = 46.44 kg
Weight of rods in Y = W2 = (d2 / 162.25) x Length
W2 = (d2 / 162.25) x 81.6
W2 = (122/162.25) x 81.6
W2 = 72.42 kg
For Waist Slab- 2,
The waist slab-2 has same dimension like, length, width, and steps. So, the total weight of steel rod required will be same as for waist slab -1.
Also, It has only one landing.
So,
Ws = 72.42 kg
For Landing,
Cutting Length of steel bar in X direction (L) = 0 meter, because we already calculated and added the quantity of rods in waist slab in x direction for both waist slab-1 and Waist Slab-2. We don’t have to add any other steel rods in x-direction of landing.
Cutting Length of one steel bar in Y direction (L) = Length of landing in Y direction – 2 x Clear Cover
(L) = 2.50 – 0.05 – 0.05 = 2.40 meter
Number of steel bars on landing in Y- Direction
Number of rod required = 1.10 / 0.1 + 1
Number of rod required = 12 Nos.
Total Length of rod = Cutting Length of one rod x Nos.
Total Length of rod = 2.40 x 12 = 28.8 meter
Therefore,
Weight of steel rods in y-direction = W3 = (d2 / 162.25) x Length
W3 = (d2 / 162.25) x Length
W3 = (d2 / 162.25) x 28.8
W3 = (122/162.25) x 28.8
W3 = 25.56 kg
For L shape steel Rod,
Length of L-shape steel rod in one step of stair,
L = 2 x (Length along Riser + Length along Trader) + Width of stair + 4 x Hook length – 2 x Bend Length
L = 2x (0.3 + 0.6) + 1.10 + 4 x 9d – 2 x 2d
L = 2.9 + 4 x 9 x 0.006 – 2 x 0.006
L = 3.104 meter
Width of stair is added to the stair because we have to add an extra straight bars to support the L-Shaped steel rods in the steps of stair.
No. of L shape steel Rod,
No. of L shaped steel rods = No. of steps in stair = 20 Nos.
Then, total length of L shaped steel = Length x Nos. = 3.104 x 20 = 62.08 meter.
Therefore,
Weight of L shaped steel rods = W4 = (d2 / 162.25) x Length
W4 = (d2 / 162.25) x 62.08
W4 = (d2 / 162.25) x 62.08
W4 = (62/162.25) x 62.08
W4 = 13.77 kg
For Top Extra Bars,
Length of one bar = L/2 = 3.35/2 = 1.675 meter
No. of bars = 2 x No. of main bar in along stair = 2 x 12 = 24 meter
It is multiplied with two because top bars are provided at top and bottom of the stair.
So,
Total length of top bars = 24 x 1.675 = 40.2 meter
Therefore,
Total weight of top bars = (d2 / 162.25) x length
W5 = (122 / 162.25) x 40.2 = 35.67 kg
Final step,
Total Weight of Steel Rod Required in the stair (W6) = Weight of main rods in waist slab-1 and Waist slab-2 + Weight of rods in Landing + Weight of steel rod at Top
(W6) = 2 x 46.44 kg + 72.42 kg + 25.56 kg +13.77 + 35.67 kg
(W6) = 240.3 kg.
Watch video on Complete bar bending Schedule
I hope this article on “Bar Bending Schedule of Dog-legged Staircase” remains helpful for you.
Happy Learning – Civil Concept
Contributed by,
Civil Engineer – Ranjeet Sahani
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