Abstract
Preserved compressive stress in concrete composite beam due to loading itself-weight on the PCa under construction works as the same reinforcement stress as prestress, and it is available to be optimal designs for concrete composite beams that choosing reinforcements between prestressing steels and steel bars balances their performances and costs. Analysis of mechanical properties of four models of concrete composite beams on Reinforced Concrete, Prestressed Reincorced Concrete and Prestressed Concrete Structures leads to the best field of prestressing rate for the designs of the beams, that is 0.5 rate. Because the preserved compressive stress works very effectively as reinforcement in this field than in the others. And concrete composite beams in this field are possible to be the most balanced ones between performance and cost.
