There are currently two acceptable methods by which concrete pipe may be designed per the AASHTO Bridge Design Specifications: the direct design method and the indirect design method. The evaluation of applied load is similar for both methods, however, evaluation of the pipe’s capacity to resist applied load differs between the two methods. The indirect design method uses physical three edge bearing (TEB) testing at the production facility based on a relationship between the forces in the pipe wall in the installed condition compared with forces in the pipe wall from the TEB test. The direct design method follows the conventional design procedure for concrete members where demand versus capacity is determined using load and resistance factors to account for variability in applied loads and resistant capacity of the structure. Because of advances in computer technology, the direct method has become easier to apply than it was in the past. However, the indirect method, which has been used for approximately 70 years, has demonstrated conservatism and is a proven design method. Comparison of similar installations using the two methods has resulted in disagreements with respect to the minimum required reinforcement, however, both methods are adequately conservative, and each may have its place depending on the size and strength of the pipe. This paper presents the fundamental differences between the two design methods and offers some guidance on when to use each of them.

目前，根据AASHTO桥梁设计规范，可以采用两种可接受的方法来设计混凝土管道：直接设计方法和间接设计方法。两种方法的施加载荷的评估相似，但是，两种方法对管道抵抗施加载荷的能力的评估不同。间接设计方法基于安装条件下管壁中的力与TEB测试中管壁中的力之间的关系，在生产工厂使用物理三边缘轴承（TEB）测试。直接设计方法遵循混凝土构件的常规设计程序，在混凝土构件中，使用荷载和阻力系数来确定需求与承载力，以考虑施加荷载的变化和结构的承载力。由于计算机技术的进步，直接方法比过去更易于应用。但是，已经使用了大约70年的间接方法已经证明了保守性，并且是一种行之有效的设计方法。使用这两种方法对类似设备的比较导致在所需的最小钢筋上存在分歧，但是，两种方法都足够保守，并且每种方法的位置取决于管道的尺寸和强度。本文介绍了两种设计方法之间的根本区别，并为何时使用每种方法提供了一些指导。已证明是保守的，并且是一种行之有效的设计方法。使用这两种方法对类似设备的比较导致在最小加固要求上存在分歧，但是，两种方法都足够保守，每种方法的位置取决于管道的尺寸和强度。本文介绍了两种设计方法之间的根本区别，并提供了有关何时使用它们的一些指导。已经证明是保守的，并且是一种行之有效的设计方法。使用这两种方法对类似设备的比较导致在最小加固要求上存在分歧，但是，两种方法都足够保守，每种方法的位置取决于管道的尺寸和强度。本文介绍了两种设计方法之间的根本区别，并为何时使用每种方法提供了一些指导。