Research On Prestressing Effects Of Prestressed Steel-concrete Composite Continuous Beam Bridge

As a new type of structure, prestressed steel-concrete composite continuous beam has the advantage of reasonable mechanical behavior, superior performance, convenient construction and economy. However, domestic and international theoretical researches are not enough on aspect of prestressed steel-concrete composite structure till now and there aren't respective provisions in the Chinese design specifications, so these aspects have a great influence on the application of this reasonable structure system.This paper presents the following substance:on the basis of setting up a finite element model of three-span prestressed steel-concrete composite continuous beams with variable cross-section ,by changing some parameters such as arrangement styles, tendon profiles, prestressed force, the effects of prestressing on ultimate flexural strength, deflection, cracking resistance load, distribution of longitudinal stress and cross-section strain, the stress increment of prestrssed tendons and elastic stability are discussed and analyzed . With a case study of Guangminggang bridge in Fuzhou , a spatial finite element model was set up, the prestressing effects on mechanic behavior of the structure are studied, the optimum plan considering prestressing effect is tested.Based on the results of theoretical research and finite element analysis, the following conclusions are drawn:1. By introducing prestressing to the steel-concrete composite continuous beam , there are many advantages,such as preventing the concrete slab from cracking, decreasing deflection and enlarging the elastic range of behavior. But due to axial force caused by prestressing, the possibilities of local buckling of the web will be larger, so ultimate load-carrying capacity of stability would be affected.2. For the introducing of bonded prestressing reinforcement in negative moment region, the cracking flexural strength of this region is improved ; the elastic scope is enlarged by applying external prestressing to steel beam, so the consumption of steel will be economized. The integrated application of two above types of arrangement style will get better performance .3. The application of prestressing increases the cracking resistance capacity as wellas the stiffness of prestressed steel-concrete composite continuous bridge ; the model considering prestressing effect is tested to be technically feasible, economical for optimized cross-section dimension of bridge structure, which deserved to be popularized and applied.