HOW TO CALCULATE STEEL QUANTITY FOR SLAB?-REINFORCEMENT CALCULATION :TWO WAY SLAB

A Vision To Clear Solutions.

SLAB REINFORCEMENT CALCULATION

One way Slab Reinforcement DetailingThe Biggest misconception is considering beam outer to outer as slab span.Please refer the below diagram.

Let's take an example of the below one way slab diagram.

Given

• Main Bars are 12mm in diameter @150mm centre to centre spacing

• Distribution bars are 8mm in diameter @150mm centre to centre spacing.(Main Bar & Distribution bar difference)
• Top & Bottom clear cover is 25mm
• Consider Development length as 40d
• Thickness of slab -150mm

One way slab Bar bending Schedule Calculation

Step-1

First ,find number of rods required for main reinforcement and distribution
Number of Bars Formula=(Length of slab/spacing)+1
Number of Main Bars=(Ly/spacing)+1=(5000/150)+1=34 nos
Number of Distribution Bars=(Lx/spacing)+1=(2000/150)+1=14 nos

Step 2
Find cutting length of main bars and distribution bars

Cutting Length of Main Bar,
= Clear Span of Slab (Lx) + (2 X Developement Length) +(1xInclined length) – (45°bend x 2)
Crank Length = 0.42 D, We have already discussed this on Cutting Length of Main Bar post
= 2000 + (2 x 40 x 12) + (1 x 0.42 x D) – (1d x 2)
= 2000 + 960 + 0.42D – (1x12x2) = 2960 +0.42D – 24

D = Slab thickness – 2 side clear cover – dia of bar = 150 – 50 -12 = 88 mm
Length of Main Bar = 2960+(0.42 x 88) – 24 = 2973 mm or 2.97 m

Step 3

Find length of distribution bar
= Clear Span (Ly) + (2 x Development Length (Ld))
= 5000 + (2 x 40 x 8) = 5640 mm or 5.64 m

Step 4

Find Top Bar (Extra) ; Top Bars are provided at the top of critical length (L/4) area,
Please refer the drawing section A-A
Number of top bars = (Lx/4) / spacing + 1 = (2000/4) / 150 +1 = 4 Nos x 2 sides = 8Nos
Length of Top Bar (L) = same as distribution bars = 5.64 m

Bar Bending Schedule for One Way Slab

S.no	Description	No.of Bars	Unit Qty	Total Qty	Diameter of Bar	Cutting Length
1	Main Bar	27	1	27	12	3.53m
2	Distribution Bar	21	1	21	8	4.34m
3	Top Bar (Ly)	5	1	5	8	4.96m
4	Top Bar (Lx)	6	1	6	8	3.96m

Two way slab Reinforcement Detailing

Now Calculate Bar Bending Schedule for Two Way Slab.

Let’s take an example the below two-way slab diagram

• Main bars are 12 mm in diameter @ 150 mm centre to centre spacing

• Distribution bars are 8 mm in diameter @ 150 mm centre to centre spacing.

• Top and Bottom Clear Cover is 25 mm

• Development length – 40 d

• Thickness of Slab – 150 mm

One Way Slab Bar Bending Schedule Calculation

Step 1

• First, find number of rods required for main reinforcement and distribution
• Number of Required Bars Formula = (Length of slab / spacing) + 1
• Number of Main Bars = Ly / spacing + 1 = (4000/150) + 1 = 27 nos
• Number of Distribution Bars = Lx / spacing + 1 = 3000/150 + 1 = 21 nos

Step 2
Find cutting length of main bars and distribution bars

Cutting Length of Main Bar,
= Clear Span of Slab (Ly) + (1 X Developement Length) +(1 x inclined length) – (45°bend x 2)
Inclined Length = 0.42 D
= 3000 + (1 x 40 x 12) + (1 x 0.42 x D) – (1d x 2)
= 3000 + 480 + 0.42D – (1x12x2) = 3480 + 0.42 D -24
D = Slab thickness – 2 side clear cover – dia of bar = 150 – 50 -12 = 88 mm
Length of Main Bar = 3480+(0.42 x 88)-24 = 3492.9 mm or 3.49 m

Step 3

Find cutting length of distribution bar

= Clear Span of Slab (Ly) + (1 X Developement Length) +(1 x inclined length) – (45°bend x 2)

Inclined Length = 0.42 D
= 4000 + (1 x 40 x 8) + (1 x 0.42 x D) – (1d x 2)
= 4000 + 320 + (0.42×88) – (1x8x2) = 4340.96mm or 4.34 m

Step 4

Find Top Bar (Extra) ; Top Bars are provided at the top of critical length (L/4) area,
Please refer the drawing section A-A

Number of Top bars on Ly side = (Lx/5) / spacing + 1 = (3000/5) / 150 +1 = 5 Nos

Length of top bar on Ly side = Clear Span of Slab (Ly) + (2 X Development Length)

= 4000+(2*40*12) = 4000+960 = 4960 mm or 4.96 m

Number of Top bars on Lx side = (Ly/5) / spacing + 1 = (4000/5) / 150 + 1 = 6 Nos

Length of top bar on Ly side = Clear Span of Slab (Ly) + (2 X Development Length)

= 3000+(2*40*12) = 3000+960 = 3960 mm or 3.96 m

Bar Bending Schedule for Two Way Slab

S.no	Description	No.of Bars	Unit Qty	Total Qty	Diameter of Bar	Cutting Length
1	Main Bar	27	1	27	12	3.53m
2	Distribution Bar	21	1	21	8	4.34m
3	Top Bar (Ly)	5	1	5	8	4.96m
4	Top Bar (Lx)	6	1	6	8	3.96m

NOTE

• Here we have taken development length as 40d. However, In practice, the structural drawing itself has this dimension or else you have to extend the rod up to the beam end minus clear cover.

Why don’t we exclude steel volume in Concrete Calculation?

A Vision To Clear Solutions.

Whenever we calculate the concrete volume to cast structural members like a beam, footing or slab, we don’t actually exclude the steel reinforcement quantity.

Reason:

Steel quantity varies anywhere from 1% – 3% of the structural member’s volume which is comparatively low. So we will neglect that.

In simple,

Take the below example,

We will calculate the required concrete volume for the above beam as,

V = L x B x D = 3 x 0.2 x 0.5 = 0.3 m³

According to the thumb rule, the concrete wastage is 3%, the reinforcement for the above example may be 3% = 0.009 m³ 

That steel reinforcement volume will be compromised with the wastage of concrete. So that we don’t actually exclude the steel reinforcement in concrete calculation

We hope you understand the concept.

CONSTRUCTION TOOLS NAMES WITH PICTURES AND USES

This post (building construction tools list) is written with the intention to make it as a go-to option for all of us.

Sometimes we know the tool but don’t know the name of them in English. We hope we all face this at least once in our life. The below list is a collective effort.

If you know some tools or have images that you think might be helpful for all of us, kindly let us know in the comment section. so we can add it here.

Let’s learn together (Don’t forget to share  )

Construction tools list with pictures

This list will be updated periodically (periodically)

Construction Tools List and their Uses

Search:

NAME	IMAGE	USES
Hoe		This tool is used to digging and to place concrete, cement mortar in head pan
Head Pan		This one is used to transport materials
Masonry trowel		This tool is used to place cement mortar
Measurement Tape		This is used to measure
Plumb Bob		This tool is used to check the vertical alignment of civil works
Wheel Barrow		This tool is used to transport cement mortar or any materials. Sometimes it also be used to measure the quantites of materials for site level concrete mixing
Concrete Mixer		This tool is used to thoroughly mix the concrete at site.
Vibrator		This tool is used to vibrate the concrete while pouring. For workability purpose, we all add water to concrete. To avoid that we are using vibrators. There are many types of vibrators
Rubber Boots		This one is used to prevent skin from chemical contact
Sand screening machine		This tool is used to sieve sand at site.
Gloves		This is used to avoid direct contact with dangerous tools, machines or to avoid any direct chemical material contact
Safety Glass		Used for safety purpose while drilling, hacking/roughening, grinding
Bump Cutter/Screed		This tool is used to level fresh concrete surface especially in slab concrete
Wooden Float/wooden rendering float		This tool is used to give a smooth finish to the plastered area
Chisel		This tool is used to remove excess or waste hard concrete
Crow Bar		This tool is used in fomwork to remove nails from boards
Framing Square		This tool is used in Brickwork, Plastering to check right angle
Framing Hammer		This tool is used to drive and remove nails
Line Level		This tool is used to check horizontal level in brickwork, plastering , flooring and tile works
Torpedo Level		Combination of line level and framing square
Cordless Drill		This tool is used to make pilot holes, replacing jumper (special type of drill should be used while drilling concrete)
Circular Saw		This tool is used to cut woods in shuttering
Hand Saw		This tool is used in wood works and shuttering
Block Plane / Jack Plane		This tool is used in Door and window wood works
Flat Pry Bar		This tool is used in shuttering sometimes used to adjust the column formwork to align
Earth Rammer		This tool is used to level the ground
Ladder
Digging bar		This tool is used to breakup and loosen the compacted / hard surface area
Polishers		This tool is used to smoothen the surface (wood or marble flooring)
Measuring Wheel		This tool is used to measure lengths. It varies by length
Measuring Box		This tool is used to measure the cement and sand while site mix
Tile Cutter		This tool is used to cut the tiles
Putty Knife		This tool is used in putty finishing to limit the thickness of the putty.
Vacuum Blower		This tools is used to clean the surface area from impurities (In flooring, Slab concrete etc.)

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