Importance of racking load for a pre-stressed concrete beam

Evaluation of cracking load for a pre-stressed concrete beam member is important for the following cases/reasons.

In some structures it may be essential that the flexural members should remain crack free even when overloaded. This may be required especially in severely corrosive environments. For such cases it shall be important to calculate cracking load for such members.

 Some code requirements stipulate that the minimum ultimate moment, a section is capable of developing, must be atleast 1.2 times the cracking moment, based upon some specified value of modulus of rupture. This is to guard against failure at cracking load.