Fundamentals of quantitative risk analysis

The scientific analysis of water distribution networks is considered an important and essential field in the design and implementation of water delivery networks for cities and populated areas around the globe. This field is enhanced by the development of computational analysis resulting from major advances in digital computers in recent decades. This allowed for some critical changes in the way consultancies, companies and businesses conduct their design, implementation and maintenance of large delivery systems that are supposed to last, reliably functional, for tens of operational years. This paper presents some of the new developments conducted in the derivation of fundamental principles for quantitative risk analysis and the techniques used to estimate the risk level factors that water networks face during all stages of their life span. The present analysis will also concentrate on the effect of simulated probabilistic pipe fractures on the performance of networks to deliver demand with a simulation period relative to the life span of the pipes. Results of risk analysis simulations for typical network scenarios showed that risk levels can be calculated in advance for any network. Those risk levels are found to increase with time, as expected. They have different pattern trends for different network connections, i.e. they can only be compared relative to some logistic changes inflicted on the same network under consideration, but have no meaning when comparisons are made between two completely different connectivity arrangements. The results also showed characteristic curves consistent with their theoretical evaluation derived, based on local segments, of star and delta arrangements of pipe connections. Those curves were seen to follow an exponential increase in risk values with time.