Dear Umer Farooq ,

In Flexure test on Doubly reinforced Concrete Beam the Allowable deflection Exceeds ,

In Tension Zone the Creaks are formed towards Both End Support only,

IF NOT the Concrete Casting and Reinforcement placing is not Done Proper.

In Compression Zone at the point of acting Load area like only Crush Shape can be seen .

Dear Ariadne Tsambani. Thank you for the document. But unfortunately that doesn't answer my question. That document doesn't express anything specifically about the theory of doubly reinforced beam except design formula.

Dear Ponkumar llango, tension occurs in a simply supported beam below the neutral axis and compression zone above neutral axis. It is obvious the cracks will be developed at the weak locations or zones of maximum shear. Will the compression  and tension zone still remain in their respective zones? How the redistribution of stresses will take place after allowable deflection exceeds in doubly reinforced beam?

Umer, there will not be any change in the behavior of doubly reinforced beam even if it just exceed the permissible limit of deflection. The permissible limit is prescribed mainly based on comfort criteria. But the deflection is 'large', i.e., the strains are large, then we need to consider the non-linear effects of large deflection, provided the beam is horizontally restrained. Then the tension- compression block start to behave differently. 

Dear Bennet Kuriakose,

when the deflection exceeds permissible limit, because of non-linear effects, how different the tension & compression blocks will behave? I mean what will change in their behaviour? That is precisely my question.

Good question.. Please share me the best answer might you trust...

Regards…