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,**

**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 = (d^{2} / 162.25) x Length

W1 = (d^{2} / 162.25) x Length

W1 = (12^{2}/162.25) x 52.33

W1 = 46.44 kg

**Weight of rods in Y = **W2 = (d^{2} / 162.25) x Length

W2 = (d^{2} / 162.25) x 81.6

W2 = (12^{2}/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 = (d^{2} / 162.25) x Length

W3 = (d^{2} / 162.25) x Length

W3 = (d^{2} / 162.25) x 28.8

W3 = (12^{2}/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 = (d^{2} / 162.25) x Length

W4 = (d^{2} / 162.25) x 62.08

W4 = (d^{2} / 162.25) x 62.08

W4 = (6^{2}/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 = (12^{2} / 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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