Parametric Study of Continuous Prestressed Composite Girders

The technique of prestressing has been used successfully to improve the performance of existing concrete structures. However, very few applications of this technique can be found in steel structures. Prestressing by means of high‐strength cable or bar can be used to effectively increase the working load and the ultimate capacity of composite steel‐concrete girders. The benefits of prestressing the steel wide flange section in composite construction can be achieved in strengthening of existing structures as well as in the design of new structures. In this paper, the elastic behavior of continuous, prestressed, composite girders with straight and draped tendon profiles is examined. The effects of design variables such as the prestress force, tendon eccentricity, and tendon length on the working load and deflection of girders are studied. The results show that the allowable load of girder increases proportionally with increase in prestress force and eccentricity. The effect of load pattern on the change in tendon force is also examined. Different prestressing sequences and resulting moments are discussed. A design example is presented to demonstrate the effectiveness of prestressing for strengthening of girders in existing composite‐steel concrete bridges.