Equal Loads are applied at the distance of one-third from both of the beam supports. It induces equal reaction same as the loading at both of the supports. Loading on beam is increased in such a manner that rate of increase in stress in the bottom fibre lies within the range of 0.02 MPa & 0.10 MPa. The lower rate being for low strength concrete and the higher rate for high strength concrete.
From the above loading configuration it is clear that at the middle one-third portion, in between two loadings, beam is subjected to pure bending. No shear force is induced within this portion. It is this portion of beam where maximum pure bending moment of Pd/2 is induced accompanied by zero shear force.
As loading increases, if fracture occurs within the middle one-third of the beam, the maximum tensile stress reached called "modulus of rupture" fbt is computed from the standard flexure formula,