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1 Introduction and backgroundPrestressed concrete cylinder pipe (PCCP) has been used for large-diameter water transmission and distribution mains in the United States as lined cylinder pipe (LCP) since 1942 and as embedded cylinder pipe (ECP) from 1952 onwards. Many classes of ECP have been standardized by the industry based on their internal fluid pressure capacity and backfill earth pressure capacity. The concrete core and prestressing wire are the main structural components, while the steel cylinder acts primarily as a water barrier. The prestressing wire wraps generate a uniform compressive force in the core that offsets the tensile stresses developed in the concrete due to the internal fluid pressure. A mortar or concrete coating surrounds the prestressing wire, embedding the wraps in an alkaline environment to protect them from external corrosive influences and physical damage such as corrosion. Breakage of prestressing wire wraps is a common occurrence in PCCP and is a result of damage due to corrosion, hydrogen embrittlement, overloading or manufacturing defects. Corrosion in immersed concrete structures can be due to earlyage cracks that leave paths for aggressive media, thus compromising the durability of the element [1], [2]. Corrosion and the subsequent breakage of an individual prestressing wire wrap reduces the strength of the pipe at that location [3]. If corrosion continues, multiple wire wrap breaks may occur in the same region, further reducing the strength of the pipe and leading to failure. Since this wire breakage is the primary cause of the structural deterioration of PCCP water mains, it is important to understand the effect of its length and location. The class of prestressing wire with its corresponding ultimate tensile strength is also an important factor for the overall strength of the pipe. Understanding the behaviour of PCCP under combined internal and external loading has gradually developed since the mid 1950s, and the evolution of the standards has been a direct result of investigations into PCCP failures [4], [5]. Although there have been significant improvements in the design and manufacture of PCCP, understanding damaged PCCP, which is intrinsic to this, is still under investigation. A study performed by Zarghami et al. [6], which compared experimental hydrostatic pressure test results with results from numerical FEM, found that the final failure mode for large-diameter PCCP was caused by increased stress in the prestressing wire wraps rather than crushing of the concrete. Liu et al.[2] presented a constitutive model for concrete hardening which considered the degree of hydration concept. The approach allowed the effects of both age and temperature on hydration to be taken into account simultaneously when modelling the early-age behaviour of underground precast concrete pipes. The study used the proposed numerical model to investigate the influences of mix design, casting scheme and curing conditions on the early-age behaviour of the pipes [2].Ojdrovic et al. [7] used finite ele...

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Prestressed Concrete Cylinder Pipes (PCCP) form the backbone of water and wastewater infrastructure networks in North America. Failure of buried PCCP is a common occurrence due to structural deterioration or manufacturing defects. To mitigate the serious effects of such failures, owners and operators of these networks use risk curves to predict the failure of PCCP when given a certain level of deterioration by field inspectors. The current problem lies in the fact that asset management using such risk curves lacks accuracy and requires costly and time‐consuming field inspections. A solution is presented in this study that bypasses the need for such risk curves by using computational modeling in conjunction with flow measurement devices installed inside pipe networks. The three‐dimensional computational model uses nonlinear finite elements to simulate the behavior of buried PCCP under combined internal and external loading. The method is validated using experimental test results of full‐scale PCCP specimens. Comparison of several key structural health indicators shows close agreement of the developed model with experimental results. The study demonstrates that the developed approach can predict with relative accuracy and time efficiency the deterioration levels of different pipe segments under realistic loading conditions. This approach eliminates the need for risk curves that require time consuming and costly field inspections, and allows for more effective asset management through on‐time maintenance and replacement of such important infrastructure facilities by their public and private owners.

In the practice of geotechnical engineering, the case of a ring footing carrying a set of concentrated point loads is a common problem. At times, the induced vertical and angular displacements for the ring footing need to be evaluated at a relatively precise level. By making use of the governing set of equations derived for the case of a general curved beam, expressions that can be easily implemented in modern computing software are derived for the vertical and angular displacements of a ring footing of rectangular cross section as functions of the radial position. The loading case considered is a vertical point load, and the soil is modelled as elastic. Estimates of the displacements have been shown for a common range of practical applications. The behaviour for a set of concentrated loads may be evaluated using the derived equations through direct superposition. Nonlinear finite element analysis is used to evaluate the vertical deflection and angular twist of the ring foundation. Numerical analysis performed for three ring foundations with different radii and cross sections is reported to validate the accuracy of the derived analytical solution.