Research On Prestressing Effect Of Externally Prestressed Steelbox-concrete Composite Continuous Beam Bridge

As a new type of structure, externally prestressed steelbox-concrete composite continuous beam has the advantage of reasonable structural behavior, superior performance. However, domestic and international researches are not enough on aspect of externally prestressed steelbox-concrete composite continuous 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.In this paper, on the basis of seting up a finite element model of three-span externally prestressed steelbox-concrete composite continuous beams with variable cross-section. By changing some parameters such as presress styles, prestressing cable profile and prestressed force, the effects of prestressing on ultimate flexural strength, deflection, cracking resistance load, distribution of longitudinal stress and cross-section strain and the stress increment of prestrssed cable are discussed and analyzed. In the mean time, with a case study of Jingshan railway bridge(48+72+48m) in Beijing 5th looproad, a spatial finite element modelwas set up. By simulating the process of construction and consulting the date of real-time testing, the restressing influence on structure is analyzed, which prove that externally prestressed steelbox-concrete composite continuous beams bridge is a kind of structure that has the advantage of reasonable structural behavior, superior performance.Based on the results of theoretical research and finite element analysis, the following conclusions are drawn:1. By introducing prestressing to the steelbox-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.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 integrated application of two above types of arrangement style will get better performance in engineering.3.The application of prestressing increases the cracking resistance capacity as well as the stiffness of prestressed steelbox-concrete composite continuous bridge. This application in actual engineering can make up the disadvantageof the general prestressing in concrete top plate, and make the distribution of prestressing more appropriate.