Question { Gammon, 60842 }

What is the exact meaning for under & over reinforced beams
& when they have to used..

Answer

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.