Doubly Reinforced Beam

The beam in which the main steel is provided on both the sides i.e. on tension as well as on the compression side, is called as doubly reinforced section.

In the following situation, doubly reinforced beams are generally preferred to constructional work:

  1.  When it is necessary to restrict the size i.e. depth and breadth of the beam section due to architectural reasons.
  2.  Whenever bending moment due to external loading is too much high. The moment of resistance of a section cannot be increased by 25% more than a balanced section.
  3.  To provide head room as in the case of basement floors or under stair cases.
  4.  When the beams are subjected to reversible loading conditions due to which bending moment is also reverse.
  5.  When the members are subjected to eccentric pattern loads on either side of its axis such as columns subjected to wind pressures.
  6.  When a member is subjected to the sudden accidental lateral loads, shock or impact i.e. rail track sleepers.
  7.  When the beam is a continuous type, then the tension occurs at the top near the supports position. Hence a section of the beam, near the support end is always designed as double reinforced beam section.