Experimental Flexural Behavior of Externally Prestressed Rectangular Reinforced Concrete Beams and Effective Parameters

External prestressing is a common rehabilitation method that has been numerically studied in the past to estimate tendon stresses. However, limited information is available on the contribution of different parameters to the ultimate response of externally prestressed beams. In this study, the effect of three parameters, including the compressive strength of concrete, cross-sectional area ratio of non-prestressed steel, and initial effective prestress on the bending strength and ductility of external prestressed concrete beams have been investigated. Ten beams with different sets of the above parameters were fabricated and loaded in a 4-point loading configuration until flexural failure. Finite element models of the specimens were developed in Abaqus and verified using test results, which were used for parametric studies. The experimental and numerical results showed that a 120% increase in concrete strength increased the ultimate load, the tendon stress gain and the ductility, by 22, 22, and 7%, respectively. A 125% increase in the ratio of non-prestressed steel increased the ultimate load by 27% but decreased the tendon stress gain, and the ductility by 26, and 38, respectively. The effective prestress force, once increased by 120%, was found to increase the ultimate load by 9% but decrease the tendon stress gain, and the ductility by 30, and 31%, respectively.