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The use of external prestressing tendons as a means of strengthening or upgrading concrete flexural members was experimentally investigated. 16 beam specimens were first subjected to cyclic fatigue loading at a constant load range to induce fatigue deformations. Then, they were externally prestressed and subjected to monotonically increasing load to failure. As a result of external prestressing, the nominal strengths of the beams were increased by up to 146 percent and the induced fatigue deflections were reduced by up to 75 percent. External tendons using a draped profile were relatively more effective in increasing the flexural strength than tendons with a straight profile. The stress ranges and mean stress levels in the internal tension reinforcement decreased considerably, which imply a significant improvement in the fatigue life of the strengthened beams.
Mohamed H. Harajli (Mon,) studied this question.