State the Loss of prestress

Loss of prestress due to elastic shortening definitely occurs in pre-tensioned concrete members. But in post-tensioned members it does not occur if all the tendons across a cross-section are simultaneously stretched, anchored and their prestresses transferred to concrete. In this case, jacks which stretch tendons butt against the ends of members. So the prestressing force which is to be transferred by tendons in already felt by the concrete member through the jacks. But post-tensioned members are subjected to this loss of prestress if all the tendons are not simultaneously tensioned. In that case, every tendon being stretched shall produce a loss of prestress in all the tendons which have already been tensioned.