Spacer bar in beam reinforcement

dear sefians

\In my opinion, spacer bars are required if there are two layers or three layers of bars at top or bottom of beams.Bond between concrete and rods are very important  and just like minimum space between rods in the same row  vertical space between  two rows of rods is also important. When you make bundled rods the bond strength is reduced as per code. If two or three rows of rods are arranged  for reinforcements in beams . you have to find the cg of of the group of rods and reduce the effective depth
accordingly in the calculation of area of steel.
A bond failure between reinforcement and concrete will certainly lead to failure of beams. therefore separators are a must when there are  more than one row of rods.
It can be one meter c/c spacing so that the two rows are  always kept straight.

regards
K. Gangadharan
structural consultant
General sponsor