DEFORMATION OF PROGRESSIVELY CRACKING REINFORCED CONCRETE BEAMS.

The theory assumes concrete to have a nonzero tensile carrying capacity, characterized by a uniaxial stress-strain diagram which characterizes progressive microcracking due to strain softening. Aside from demonstrating a good agreement with available test data for short-time deformations up to the ultimate load, the theory also correctly predicts the longtime creep deformations of cracked beams. The theory also predicts the reduction of creep deflections achieved by the use of compression reinforcement, and a comparison of modeling this effect is made with an ACI formula. As a simplified version of the model, it is proposed to replace the tensile strain-softening behavior by the use of an equivalent tensile area of concrete at the level of tensile steel, behaving linearly. Assuming this area to be a constant, realistic predictions for short-time as well as longtime deformations in the service stress range can still be obtained.