Effect of Various Bedding Conditions on Structural Integrity of Prestressed Concrete Cylinder Pipe

Abstract

Prestressed Concrete Cylinder Pipe (PCCP) is one pipe material mainly used in large-diameter and high-pressure transmission main or force main. PCCP was widely used in large utilities because of its low cost and relatively good performance in its early stage of life. However, as PCCP approaches to the end of life, more failures occur. PCCP failures usually occur suddenly without any warning and cause catastrophic consequences, including great economic, societal, and environmental losses. Many factors can cause PCCP failures including design and manufacture, construction and operation, and environmental factors. Among these factors, bedding condition has been identified in forensic studies as a critical factor, especially in mountain areas with rock bedding. However, PCCPs are generally assumed to be rigid pipe and they are placed in poor bedding in some constructions, thus causing pipe failures. In current numerical models used to evaluate structural condition of PCCP, one of the major limitations is inadequate consideration of bedding conditions. This paper analyzes the effect of various bedding conditions on structural integrity of PCCP. A numerical model is developed and the properties of different bedding materials are considered. The pipe components such as coating, prestressing wires, concrete core, and steel cylinder are taken into account. The results of the analysis are summarized and compared. The research presented in this paper provides a better understanding of the importance of good bedding for PCCP. The findings of this research can help utilities better management their PCCP pipelines in various bedding conditions.