Guide to Design of Simply Supported Slabs | Design of RCC Structures

Guide to Design of Simply Supported Slabs | Design of RCC Structures

What are Simply Supported Slabs?

Simply supported slabs are supported on columns or stanchions. They have support on all four sides.

Simply supported slabs are classified as One way slabs and Two way slabs.

One way slabs bend in one direction only and transfer their loads to the two support beams in opposite directions. Their main steel in on shorter span length. L/B ratio is generally less than 2.

Two way slabs bend in both directions, and transfer their loads and stresses on all four sides. L/B ratio is equal to or greater than 2.

Simply supported slabs don’t give adequate provision to resist torsion at corner to prevent corner from lifting.

The maximum bending moment will be given if the slabs are restrained. But atleast 50% of the tension reinforcement provided at the mid span should extend to the support. The remaining 50% should extend to within 0.1Lx or Ly at the support as appropriate.

You can use a free app to design simply supported RCC Slab panel.

RCC Slab Design depends on the on the dimensions of the slab after which the slab is termed as a one-way slab or a two-way slab…

In the design of RCC structures, Column Design and Beam Design are to be done before we start with RCC Slab Design…

Basic Rules followed in the design of simply supported Slab

Thickness of slab

l/d ratio should be less than the following:

• Simply supported slab

• Continuous slab, l/d = 26

• Cantilever slab, l/d = 7

In any case of the above, the thickness should not be less than 100mm

Effective span

• Distance between centre to centre of support

• Clear span plus effective depth

Minimum main reinforcement

• 0.15% gross c/s of slab – for MS bars

• 0.12% gross c/s of slab – for HYSD bars

Spacing of main bars

The spacing or c/c distance of main bars shall not exceed following:

• Calculated value

• 3 x d

• 300mm

Distribution or Temperature reinforcement

This reinforcement runs perpendicular to the main reinforcement in order to distribute the load and to resist the temperature and shrinkage stresses.

It should be atleast equal to;

• 0.15% gross c/s of slab – for MS bars

• 0.12% gross c/s of slab – for HYSD bars

Spacing of distribution bars

The spacing or c/c distance of distribution bars shall not exceed the following

• Calculated area

• 5 x d

• 450mm

Diameter of bars

The diameter of the bars varies from 8mm to 14mm and should not exceed 1/8th of the overall depth of the slab.

For distribution steel, the diameter varies from 6mm to 8mm.

Cover

The bottom cover for reinforcement shall not be less than 15mm or less than the diameter of such bar.