Concrete Beams with Prestressed Reinforcement

Tests on six rectangular beams reinforced with variable amounts of deformed steel bars and precast prestressed concrete prisms are reported. Methods are suggested for computing the moment causing cracking of the in situ concrete and that causing cracking of the prestressed reinforcement. After cracking of prestressed reinforcement, and up to commencement of yield of nonprestressed tension reinforcement, flexural analysis could be done using same assumptions of classic working stress design by associating to the combined area of strand and deformed bars a Pseudo Modulus of Elasticity E_ps higher than that of ordinary steel E_s. During that stage it was found that for similar beams with equal total areas of tension reinforcement, the ratio between their maximum crack widths was practically equal to the inverse of their respective Pseudo Moduli. Strain hardening effects should be taken into consideration in estimating ultimate moment capacity of beams reinforced with such composite reinforcement.