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Casting of Plinth Beam 1

This document discusses the casting of a plinth beam. It defines a plinth beam as a reinforced concrete beam constructed above the foundation but below walls that takes the load of walls built on top of it. It describes forming the beam, mixing concrete with a 1:3:6 ratio and 25mm aggregate, and properly compacting the concrete. The purpose of a plinth beam is to prevent differential settlement, dampness from entering the building, and cracks propagating from the foundation to walls. It should have a minimum strength of 20MPa.

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RAJA BASUMATARY
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3K views8 pages

Casting of Plinth Beam 1

This document discusses the casting of a plinth beam. It defines a plinth beam as a reinforced concrete beam constructed above the foundation but below walls that takes the load of walls built on top of it. It describes forming the beam, mixing concrete with a 1:3:6 ratio and 25mm aggregate, and properly compacting the concrete. The purpose of a plinth beam is to prevent differential settlement, dampness from entering the building, and cracks propagating from the foundation to walls. It should have a minimum strength of 20MPa.

Uploaded by

RAJA BASUMATARY
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Central Institute of Technology,Kokrajhar

(Deemed to be university under MHRD,Govt.of india)

783370 Kokrajhar,BTR,Assam,INDIA

A Project Report
On
“Casting of plinth beam”

Submitted by: Akhrangsa Basumatary (CIT/18/CT/023)

DEPARTMENT OF CIVIL ENGINEERING


Contents

 Introduction.

 Formwork for Plinth Beam

 Purpose of Plinth Beam

 Application of a Plinth Beam

 The Casting of the Plinth Beam

 Concrete Strength Suitable for Plinth Beam Construction

 Conclusion.
INTRODUCTION
As a way of reducing cracks and collapses in building, designers adopted a method of

casting two different beams (ground beam and plinth beam); the former is cast after the trench

is excavated to tie the column starters while the latter is cast above the substructure wall to

give more strength to the foundation of the building.

Now, we are going to discuss plinth beam in detail.

A plinth beam is a reinforced concrete beam constructed above the foundation but

below its wall. It is a beam in a framed structure provided at or above ground level that takes

the load of the wall built on top of it.

Fig : A cast plinth beam


Formwork for Plinth Beam

The shutters used for plinth beam construction should be installed carefully and properly, it

should be secured adequately prior to concrete placement.

Fig : Installation of Shutters for Plinth Beam Formwork

Purpose of Plinth Beam

(1) It prevents differential settlement in structures because all the load coming on the plinth

beam is uniformly transferred to the foundation.

(2) It prevents the dampness from the foundation to enter the building.

(3 ) It ties all the column.

(4) It prevents cracks from the foundation to reach the wall.

(5) It prevents the building to collapse during an earthquake.

(6) Plinth beams distribute the load uniformly.


Application of a Plinth Beam

(1) It is mandatory to have a plinth beam in area that is prone to earthquake.

(2) Construction of a plinth beam above the ground level is another application of a plinth beam.

The Casting of the Plinth Beam

The plinth beam to be cast with the mix ratio of 1:3:6 with aggregate size of25mm in

diameter with strength not less than 20MPa. The concrete to be placed properly to avoid

segregation .The concrete should be compacted sufficiently using a poker vibrator to expel air

and voids as well as to prevent steel bars from aggressive elements.

Fig : Placement and Compaction of Concrete for Plinth Beam


Concrete Strength Suitable for Plinth Beam
Construction
The strength of plinth beam concrete according to BS 8110 shall not be smaller than

20MPa i.e grade 20 characteristic strength. However, if the mixing is done manually, about 20%

cement needs to be added to the initial quantity of cement. This is done to avoid loss of

concrete strength. The mix ratio for the casting should be 1:3:6 .

Fig : The Mixing of the Plinth Beam Concrete


Conclusion

Plinth beam is provided to prevent the extension or propagation of cracks from

the foundation into the wall above when the foundation suffers from settlement. Plinth

beams distributes the load of the wall over the foundation evenly.

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