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体外预应力筋在结构加固以及钢混组合结构中应用广泛,但是针对该类结构受力特性的分析方法并不完善,主要原因是在外荷载作用下,预应力筋与结构会产生相对滑移,传统分析方法中截面上应变协调的假设无法继续采用。体外预应力筋由于结构变形导致的应力增量是体外预应力筋分析理论中的一项重要内容,目前已有的应力增量计算方法,大多只适用于特定结构形式,或者没有考虑预应力筋在转向块处的滑移,局限性大。该文充分考虑体外预应力筋在转向块处的滑移,通过分析预应力筋的变形与结构整体变形的几何关系并进行线性化,导出了通用的体外预应力筋应力增量的计算公式,得到了其刚度矩阵的显式表达式,并构造了适用于考虑滑移的体外预应力筋的有限单元,在此基础上还提出了体外预应力筋应力增量的简化计算方法。最后通过数值算例验证了该文方法,结果表明该方法使用简便,精确度高。
External prestressing tendons are widely used in structural reinforcement and steel-concrete composite structures. However, the analysis methods for the stress characteristics of such structures are not perfect, mainly due to the relative slip of tendons and structures under the external load, The assumption of strain co-ordination in the conventional method can not be used any more. The stress increment of prestressed tendons due to structural deformation is an important part of the theory of prestressed tendons in vitro. At present, the existing methods for calculating stress increments are mostly applicable only to specific structural forms or not considering prestressed tendons The slip at the steering block has great limitations. In this paper, the slip of prestressing tendons in the steering block is fully considered. By calculating the geometric relation between the deformation of prestressing tendons and the overall deformation of the structure and the linearization of the prestressing tendons, a formula for calculating the stress increment of prestressed tendons in vitro is derived. The explicit expression of its stiffness matrix is obtained and the finite element suitable for considering the external prestressing tendons under slip is constructed. Based on this, a simplified calculation method for stress increment of external prestressing tendons is proposed. Finally, a numerical example is given to verify the method. The results show that the method is simple to use and has high accuracy.