Singly Reinforced Beams:
A singly reinforced beam is a beam provided with longitudinal reinforcement in the tension zone only.
The analysis and design of a reinforced concrete member subjected to bending are based on the following assumptions:
1) Plane sections transverse to the centre line of a member before bending remain plane sections after bending.
2) Elastic modulus of concrete has the same value within the limits of deformation of the member.
3) Elastic modulus for steel has the same value within the limits of deformation of the member.
4) The reinforcement does not slip from concrete surrounding it.
5) Tension is entirely by steel.
6) The steel is free from initial stresses when embedded in concrete.
7) There is no resultant thrust on any transverse section of the member.
Doubly Reinforced Beams:
Beams reinforced with steel in compression and tension zones are called Doubly reinforced beams.