简支梁体外预应力加固应力增量计算

Calculation of Stress Increment on External Prestressing Reinforcement for Simply Supported Beam

体外预应力技术是加固既有预应力混凝土桥梁最有效的方法之一,可大幅提高原桥刚度及承载能力并克服其他加固方法中难以克服的二次受力问题。利用结构变形前后的几何关系,提出了在车道荷载作用下三折线布筋形式的体外预应力应力增量计算公式,进而推导了单折线、直线布筋形式的体外预应力增量的计算公式,计算公式的物理意义明确,可计算不同荷载下的体外预应力应力增量。通过一座预应力混凝土简支T梁的加固设计实例,计算了体外预应力在车道荷载作用下的应力增量及施工阶段、使用阶段梁的上下缘混凝土应力,为简支梁的体外预应力加固工程提供了理论技术支持。

External prestressing technique is one of the most effective way to reinforce the existing prestressed concrete bridge, which can significantly improve the rigidity and load carrying capacity of the original bridge and overcome the difficulty of the secondary force issues which may hard to solve by other strengthening method. By using the geometric relationship of structure before and after deformation, this paper puts forward the external prestressing stress increment calculation formula of three line under the lane load distributed, then derives the computation formula for single line and linear layout of external prestress increase,which have a clear physical meaning, and can be used to calculate external prestressing stress increment under different load. In this paper, through the instance of reinforcement design on an actual prestressed concrete simply supported T-beam, the stress increment of externally prestressed under lane load and the concrete stress of the edge of the beam on construction stage and service phase are calculated, which could provide a good theoretical and technical support for externally prestressed reinforcement of simply supported beam.