ABSTRACT
ABSTRACT: The prestressing technique using external tendons can be considered an effective method of strengthening bridges that are deteriorating due to increasing overloading and progressive structural aging. This technique is not only easy to perform but it is also convenient to maintain the tendon because it is exposed in the air; it is a practical and cost-effective strengthening method (Troitsky et al. 1989). The advantages of the technique are the enlargement of the elastic range of behavior, the increment of the ultimate capacity, and improvement of the fatigue and fracture strength (Saadatmanesh et al. 1989a, b, c). Therefore, prestressing is applied to the reinforcement of many concrete girders (Harajli 1993, Ng 2003). In order to achieve an more economical and effective strengthening, design variables such as configuration of tendon, the number of tendons and the initial tendon force have to be determined effectively to reinforce an existing bridge with external tendons.
