Cracked Moment of Inertia and Yielding of Reinforced Concrete Beams

Once a reinforced concrete beam is cracked, the section reduces dramatically from the gross moment of inertia to the cracked moment of inertia. This cracked section is active from the cracking moment up until the yielding moment, when the steel yields. Computing the cracked moment of inertia is important for finding deflections of concrete beams under service loads.