Question

Prove qualitatively that the compression reinforcement will increase the deformation capacity (i.e. ductility) of any RC section?  

Answer 1

1. When compression reinforcement is provided than it will increase the bond strength between concrete and the reinforcement.

This increase in bond strength will result in prevention of movement of concrete.

If the reinforcement provided in the compression side and tension side is equal than it will prevent the shrinkage deflection because the concrete will shrink equally on top and bottom side.

If we add 2% of compression reinforcement than it will reduce the deflection up to 45%-50 %

2. Compression reinforcement also help in increase in shear strength of the beam and they act as hanger bar for stirrups.

3. A doubly reinforced beam will have a lower overall depth which will also result in decrease in deflection as it reduces the dead weight of beam.