Deflections of partially prestressed concrete beams are analyzed on the basis of bending theory with plane cross sections, taking into account not only plasticity of steel and nonlinearity of concrete in compression, but also the tensile strain softening of concrete. The results agree with previous experiments quite well, and better than calculations in which the tensile stresses in concrete are neglected. However, their effect is not very large and is much less than that previously found in Balant and Oh 's analysis of nonprestressed concrete beams. The effect of tensile strain softening is found to be significant only in the initial post-cracking response (cracked elastic stage) and vanish near the ultimate load. The effect of tension stiffening of steel due to the surrounding concrete and the associated bond slip is neglected, since the discrepancy from test data which could be ascribed to this phenomenon is quite small and adequate agreement with tests in the initial post-cracking stage is found without tension stiffening. Comparisons are also made with the l-effective method of Branson and Trost, although generally these predictions are softer than measured and become unacceptable near the ultimate load. Comparisons of calculations as well as measurements between beams with bonded and unbonded reinforcement show a relatively small difference.
