Double Reinforced beam or doubly reinforced beam is the beam having reinforcements both the bottom and top.
The singly reinforced beam has tension reinforcements placed only at the bottom of the beam. In a singly reinforced beam, tension is carried by steel, and compression is carried by the concrete.
In doubly reinforced beams, tension reinforcements are provided at the bottom and the compression reinforcements are provided at the top. This type of beam is mostly used when the depth of the beam is restricted.