Risk-based Replacement Strategies for Deteriorating Reinforced Concrete Pipes

Water distribution networks comprised of underground reinforced concrete pipes deteriorate with time due to environmental conditions, such as chloride-induced corrosion and differential soil movements [1]. If the pipes in these networks are not periodically replaced, they will eventually fail. Strategies for replacement for these pipes depend on 1) the risks associated with failure of a water distribution network, and 2) the costs associated with replacing the pipes, including the cost of removing existing pipes, the cost of the new pipes and the cost of service interruption if there is any temporary closure [2]. This paper gives an example of how predictive models of the deterioration of reinforced concrete pipes and the consequences of failure can be used to develop risk-based replacement strategies for underground reinforced concrete pipe networks. Replacement strategies are determined for a series network consisting of 1500 underground reinforced concrete pipes. The variation in cumulative overall costs of choosing the replacement times for each pipe group is shown, with and without discount rate. This paper also shows the importance of correctly modelling the deterioration speed by analysing the example series network for three different deterioration speeds. The possible cost savings by accurately estimating the deterioration speed are shown. The main conclusion is that the use of accurate predictive models in the determination of replacement strategies for underground reinforced concrete pipe networks, the approach used by Oxand S.A, can result in significant savings in cumulative overall costs.