What would happen if the extra top and extra bottom is not provided in the RCC beam?

We all know that beam behaves differently at mid span and at support ends. The mid-span beam generate positive bending moment and end support generates negative bending moment. The purpose of extra at top at support end and extra bottom at mid span is to negate the moment.

If we provide complete end to end length instead of extra reinforcement the consumption of steel will unnecessarily increase, since one need not provide and only provision of small extra at these location will be an effective solution.

• Concrete cover for steel bar is much necessary to protect the steel against corrosion (rusting) and to provide resistance against fire.

• If fire occurs in the building, the steel might lose so much strength to impair its reinforcing effect and the beams might collapse.

• When the numbers of steel bars are more, than spacer between the bars must be used.

• To keep crank bar in position, support of required height may be used under crank bar in the RCC slabs.

Trust this explains.