1. What is a spacer bar in the beam?
A piece of a steel bar provided in between the two layers of the main reinforcement in the beam is called a spacer bar. They are inserted perpendicularly or in a tapered position in between the two layers.
2. Why the spacer bars are provided in the beam reinforcement?
As the name suggests, spacer bars are provided to maintain a uniform gap between the two reinforcement layers. Usually, the maximum size of the coarse aggregates used in the beam concreting is 20mm. The spacer bar maintains a gap between the bars for the easy flow of the concrete aggregate, which otherwise would have created voids in between the bars.
Due to the spacer bars, the concrete gets filled in between the bar layers to provide adequate bond strength as required by the beam.
3. What should be the spacing & diameter of the spacer bars?
Always, the diameter of the spacer bar should be above the maximum size of the aggregates used in concrete. Suppose if the aggregate size is 20mm., the dia. of the spacer bar should be 25mm. or 32mm.
The spacer bars should be placed at a c/c distance of 1000mm. from each other.
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4. How to calculate the cutting length of the spacer bar?
Let us calculate the cutting length of the spacer bar for the below-given drawing.
Given data:
Beamwidth = 450mm.
Beam depth = 600mm.
Clear cover = 25mm.
The cutting length of the spacer bar
=[{ beam width - ( 2nos. × clear cover )} +10mm.]
= [ { 450mm. - ( 2nos × 25mm.)} +10mm.]
= [{400mm.} + 10mm.]
= 390mm.
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