Parametric Study of the External Strengthening of Composite Beams Using Post-Tensioned Tendons

Post-tensioning by means of high‐strength tendons can be used to effectively increase the ultimate capacity of steel-concrete composite beams. In this paper, a numerical model is presented to simulate the nonlinear flexural behavior of composite beams strengthened with externally post-tensioned tendons. The accuracy of the developed numerical model is validated using existing experimental tests. The influence of various strengthening parameters is investigated to show the effect of the tendon profile, the tendon length, the degree of shear connection, and the fatigue loads on the response of the strengthened beams. The results demonstrate that the trapezoidal profile shows better behavior for the strengthened beams than the other profiles at the same tendon eccentricity. Applying post-tensioning along the full length of the beam helps to reduce the creation of fatigue cracks, which always start at stress raisers, and consequently increases the fatigue strength of the composite beam. It is observed that 80% degree of shear connection or higher is recommended to obtain the desired performance of the external post-tensioning force. Also, external post-tensioning effectively improves the flexural behavior of the strengthened beam under fatigue loads.