Abstract
The effective moment of inertia of cracked rectangular reinforced concrete beams with different reinforcement ratios under a midspan concentrated load was evaluated experimentally from their immediate deflections. Comparison of the test results with values obtained using the ACI Building Code equation of the effective moment of inertia showed a noticeable difference, especially for heavily reinforced sections. This difference was accounted for by modifying the exponent in the effective moment of inertia equation. The effect of using the moment of inertia of the uncracked transformed section in the computation of the effective moment of inertia was also discussed. In addition, the effect of the reinforcement ratio was incorporated in a recently developed model which estimates the effective moment of inertia of reinforced concrete beams under any type of symmetrical loading by considering the variation in the beam's cracked length.