Rcc slab design

*RCC Slab Design Guidelines:-

a) Effective span of slab:-

Effective span of slab shall be lesser of the two

1. L = clear span + d (effective depth )

2. L = Center to center distance between the support

b) Depth of slab:-

The depth of slab depends on bending moment and deflection criterion. the trail depth can be obtained using:

Effective depth d= Span /((L/d)Basic x modification factor)

For obtaining modification factor, the percentage of steel for slab can be assumed from 0.2 to 0.5%.

The effective depth d of two way slabs can also be assumed using cl.24.1,IS 456 provided short span is 3.5m and loading class is <3.5KN/m2
Type of support

Simply supported

Fe-250 – L/35

Fe-415 – L/28

Continuous support

Fe-250 – L/40

Fe-415 – L/32

Or, the following thumb rules can be used:

One way slab d=(L/22) to (L/28).

Two way simply supported slab d=(L/20) to (L/30)

Two way restrained slab d=(L/30) to (L/32)

c) Load on slab:-

The load on slab comprises of Dead load, floor finish and live load. The loads are calculated per unit area (load/m2).

Dead load = D x 25 kN/m2 ( Where D is thickness of slab in m)

Floor finish (Assumed as)= 1 to 2 kN/m2

Live load (Assumed as) = 3 to 5 kN/m2 (depending on the occupancy of the building)

*Detailing Requirements of RCC Slab as per IS456: 2000

a) Nominal Cover:-

For Mild exposure – 20 mm

For Moderate exposure – 30 mm

However, if the diameter of bar do not exceed 12 mm, or cover may be reduced by 5 mm. Thus for main reinforcement up to 12 mm diameter bar and for mild exposure, the nominal cover is 15 mm.

b) Minimum reinforcement:- The reinforcement in either direction in slab shall not be less than

0.15% of the total cross sectional area for Fe-250 steel

0.12% of the total cross-sectional area for Fe-415 & Fe-500 steel.

c) Spacing of bars:- The maximum spacing of bars shall not exceed

Main Steel – 3d or 300 mm whichever is smaller

Distribution steel –5d or 450 mm whichever is smaller Where, ‘d’ is the effective depth of slab. Note: The minimum clear spacing of bars is not kept less than 75 mm (Preferably 100 mm) though code do not recommend any value.

d) Maximum diameter of bar: -The maximum diameter of bar in slab, shall not exceed D/8, where D is the total thickness of slab.

BEST INFO ABOUT BATHROOM SIZE AND SPACE ARRANGEMENT

BEST INFO ABOUT BATHROOM SIZE AND SPACE ARRANGEMENT

Maximum distance between two RCC columns

MAXIMUM DISTANCE BETWEEN TWO RCC COLUMNS?

Normal distance b/w two RCC columns is 5 meter Or 16 feet.

Maximum distance b/w RCC columns is 7.5 meter or 24 feet.

Minimum distance b/w 2 RCC columns is 2.5 meters or 8 feet.

Remember that for normal load such a domestic house we can take distance b/w 2 RCC columns = 5 meter.

If we take distance b/w two columns 7.5 meter than we will increase the width and depth of beam.
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How to calculate quantity of steel for beam

HOW TO CALCULATE QUANTITY OF STEEL FOR RCC BEAM , COLUMN AND SLAB?

WE KNOW THAT:

MINIMUM PERCENTAGE % OF STEEL AS PER INDIAN STANDARD ARE GIVEN BELOW.

1: For Column = 0.8% of Cross Section of Column

2: For Beam = As = 0.85bd / fy    of cross section area.  ,      where   As for Area of steel.

3: For Slab = 0.12% of Total area of slab.

Maximum Steel as a per Indian Standard are given below.

For Column = 6% of Cross Sectional Area of Column



For Slab = 4% of Cross Sectional area of slab.

For Beam = 4 % of Cross sectional are of beam.

From above formulas you can find the quantity of steel for different structures.
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How to find depth of foundation for building

HOW TO FIND DEPTH OF FOUNDATION FOR BUILDING?

**USE GIVEN FORMULA TO FIND DEPTH OF FOUNDATION:

From Rankine’s Formula,

Depth = p/w (1-sin$/1+sin$)
Where,
p=total load on foundation
w=unit wt of soil
$ = angle of repose of soil
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REMEMBER SOME POINTS BEFORE STARTING CONCRETING IN FOOTING

 

Pile cap foundation

Pile cap foundation

Building material

Rcc slab for roof casting