Post – tensioned Concrete SlabsMade by:Aakash Mohan

Pre-stressing is defined as a method of applying pre-compression to control the stresses resulting due to external loads. The principle behind pre-stressed concrete is that compressive stresses induced by high-strength steel tendons in a concrete member before loads are applied will balance the tensile stresses imposed in the member during service.

Introduction to Pre-stressing

There are two types of pre-stressing methods. 1. Pre-tensioning 2. Post-tensioning Post- tensioning is again classified in to two types 1. Bounded post tensioned concrete 2. Unbounded post tensioned concrete

It is basically a pre-stressed concrete slab casted through post-tensioning method.Post-tensioned concrete slabs

Advantages of PT Slabs 1. Higher load carrying capacity 2. Reduced cost 3. Flexibility in design 4. Lesser usage of materials 5. DurabilityDisadvantages of PT slabs 1. Corrosion of the tendons 2. Complexity of work 3. Poor workmanship may lead to future mishaps

The various types of PT flat slabs are – 1. Solid flat slab 2. Solid flat slab with drop panels 3. Banded flat slab 4. Ribbed slab 5. Coffered flat slab

All have nearly same advantages and disadvantages, but are used in different conditions

Types of PT flat slabs

1. Flexibility in room layout2. Reinforcement placement is easier.3. Ease of Framework installation.4. Building height can be reduced.5. Less construction time.6. Prefabricated welded mesh.7. Usually does not require shear

reinforcement at the columns.

Advantages of flat slab

1. Span length is medium.2. Not suitable for supporting brittle (masonry) partitions3. Use of drop panels may interfere with larger mechanical ducting4. Critical middle strip deflection5. Higher slab thickness

Disadvantages of flat slab

This is the simplest flat slab in which the slab load is directly transferred on the columns.

Applicability : 1. For relatively light serviceable loads e.g. residential buildings, office buildings, hotels, hospital and parking areas, large halls, library 2. For spans ranging from (5-12) m.

Solid flat slab

Solid flat slab

In this type of flat slab, there is a drop panel between the slab and column.

Applicability :1. For spans up to 16m2. Other conditions same as solid flat slab

Solid flat slab with drop panels

Solid flat slab with drop panels

Applicability :1. For one way slabs (for building

spanning in one direction)2. For moderate working loads3. Mainly for business centres, parking

areas and schools4. Also used in case of cantilever span,

for span up to 16m

Banded flat slab

Banded flat slab

Applicability :1. Used in case of heavy loads2. Mainly used for malls, industrial

buildings, railway station and airport buildings

3. For span ranging from 10-20 m.

Ribbed flat slab

Ribbed flat slab

Applicability :1. Same as ribbed flat slab

Coffered flat slab