Answer / prakash

In singly reinforced section main steel is at bottom for
tensile stresses. while in case of doubly reinforced
section it is on both sides for comp and tension.

Answer / b.murali krishan

Singly reinforced section the reinforcement is provided to
care tension in the bottom of beam further singly reinforced
members or beam are classified as underreinforced
section,balaced section and overreinforced section.If the
moment of resistance of the section is equal to the bending
moment than it a balaced section,moment of resistance of the
section is more than that of bending moment than it a
overreinforced section and If the moment of resistance of
the section is less then the bending moment than it a
underreinforced section.Doubly reinforced section is to be
designed to restrict the depth of beam(section) in case of
head room condition or if the bending moment is more than
25% of moment of resistance of the section doubly reinforced
section is to designed. in doubly reinforced beam or section
the reinforcement is to be provided both in compression and
tension zones.

Answer / chaitanya chauhan

the basic difference between a singly reinforce section and
a doubly reinforce section is that in case of singly
reinforce section the reinforcement bars are provided only
in tensile zone whereas in case of doubly reinforce section
reinforcement bars are provided in tensile as well as in
compression zone.

Answer / nagori salim

Singly reinforced section;
Steel at bottom of section to take TENSION force.

Doubly reinforced section;
Steel is provided at top & bottom zone i.e (Tension &
Compression zone resp.)


Reason:

Steel provided in top zone reduces cross sectional
dimension, section is safe against REVERSAL moment.

Answer / komal.b

The difference between a singly and doubly reinforced beam
is that, in singly reinforced beam the reinforcement is
provided in tension zone only.But in some cases concrete
may not be able to withstand the compressive forces acting
on it and if applied bending moment is more than the moment
of resistance than reinforcement is provided in compression
zone also, which means doubly reinforced. Hence in doubly
reinforced beam, reinforcement is provided in both tension
and compression zone.

Answer / beig naseer

Beam is generally a flexural member which resist load
mainly by bending.Singly reinforced beam have steel
reinforcement in the tension zone but in doubly reinforced
beam steel reinforcement is provided in the tension as well
as in compression zone.

Answer / naveen kumar singh

When the depth of beam is restricted
then we use doubly reinforced beam
otherwise we used singly reinforced beam

Answer / saikat ganguly

in case of singly reinforced beam, the reinforcement is provided in the bottom i.e the tension zone to take care of the tension. but at the same time dummy reinforcements are provided at the top in order to tie the bars using stirrups.

In case of doubly reinforced beams, reinforcement is provided in both tension as well as in the compression zone

Answer / aziz ul hakeem

Singly Reinforced Beams:
Ductile failure is always desirable and brittle failure should be always avoided.
Most beams in real life structures are Singly Reinforced Beams where steel bars are provided only in the Tension Face (hanger bars in the compression zone to hold the stirrups are not for structural reasons).
An upper limit on the amount of steel in Tension Zone is imposed to make sure that the failure should be always ductile. This is generally called As-max (based on pmax) which is about 75% of the balanced steel ratio or steel reinforcement.
Doubly Reinforced Beams:
However in real life situations where it is not possible to increase the beam depth and the applied bending moments are greater than the beams capacity with the As-max then we go for doubly reinforced beams. First the total amount of steel reinforcement is calculated and then the steel in excess of the As-max is provided both in the tension and compression zones. i.e. if 3 no. 8 bars, in excess of the As-max, are required in the tension zone then 3 no. 8 bars should be provided in compression zone and As-max+3 no. 8 bars should be provided in the tension zone.
Example:
In tension face/zone – Reinforcement Steel = As-max+3 no. 8 bars
In compression face/zone – Reinforcement Steel = 3 no. 8 bars

Answer / gulab singh

In singly reinforced beam,steel bars are provided in tensile zone,whereas in doubly reinforced beam steel bars are provided in tensile as well as in compressive zone.
Doubly reinforced beam is more advantageous than singly reinforced beam on the view of depth of beam.Depth of beam decreases in singly reinforced beam.

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