Answer / naveen k. singh

when moment of resistant of a section is gteater than the
design moment then section is designed for under reinforced
section/beam.
when moment of resistant of a section is less than the
design moment then section is designed for over reinforced
section/beam.
OR
when Ast of a section is greater than Ast for balanced
section then section is called OVER REINFORCED section.

when Ast of a section is less than Ast for balanced section
then section is called UNDER REINFORCED section.

Answer / abhinay barla

when the permissible stress is less than the maximum permissible value then it is said to be under reinforced section/beam.

when the permissible stress is grater than the maximum permissible value then it is said to be over reinforced section/beam.

when the permissible stress is equal to the maximum permissible value then it is said to be balanced reinforced section/beam.

Answer / sahil sharma

under reinforced beams are those in which less reinforcement
is provided as compared to balanced section,these are
provided when design moment is less than max moment of
resistance(which is provided by balanced section).
over reinforced beam is just reverse of above.these are
provided when we have extra steel (or money) to waste.over
reinforcement doesn't mean that it will provide extra strength.

Answer / terabaap

when Ast provided is more than that of a balanced section,
its over reinforced. its not permitted by code as it doesnt
give warning before failure.
Under reinforced - Ast provided is less than that of a
balanced section.
in both cases, failre is by crushing of concerte only.

Answer / madan

A section in which the actual stress in the reinfircement
reaches the full allowable value before the extream fiber
of the concrete is subjected to full allowable stress is
calle under reinforced section. and vice- versa called over
reinforced section

Answer / k.sathiyaraj

reinforcement provided within the yielding limit is called
under reinforced beam.

reinforcement provided along the yielding limit is called
over reinforced beam.

Answer / rahul

In this under reinforced section amount of stell is kept less than that in the balanced section and the N.A 'X' moves upward to satisfy the equilibrium condntht force of compression is equal to force of tension.and the failure is called tension failure bcoz yielding of steel was responsible for continued higher strains in cncrte...Now for over reinf. The amount of steel is kept more than tht in the balanced condisn..the N.A axis tends to move downward and strain in steel remains in the elastic region in case of under strain increases..in this part failure takes place due cncrte crushes and the steel is still well within elastic limit..that is compression failure takes place..

Answer / khandelwal

Underreinforced design is a design in which the steel reinforcement is lesser than whati s requited for balanced condition. If the ultimate load is approached, the steel will begin to yield although the compression concrete is still under stressed. If the load is further increased, the steel will continue to elongate, resulting in appreciable deflections and large visible cracks in the tensile concrete. Failure under this condition is ductile and will give warning to the user of the structure to decrease the load.
Over reinforced design is a design in which the steel reinforcement is more than what is required for balanced condition. If the beam is over reinforced, the steel will not yield before fai}ure. As the load is increased,deflections are not noticeable although the compression concrete is highly stressed, and failure occurs suddenly without warning to the user of the structure.

Answer / dinusha samarasinghe

reinforced concrete beam section in which the failure stain in concrete is reached earlier than tha yeild stain of steel is reached are called over r/f section

R/F concrete section which the steel reaches yeild stain at loads lower than the loads at which the concret reaches failure strain mean by under R/F section

Answer / bharath

generally all the sections are designed to be balanced section. under reinforced section means the steel is less than the balanced one's where the structure is ductile(warning can be seen before failure)
.if it is over reinforce i,e steel is more than the required then the structure may fail under brittle (sudden collapse)

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