Environmental Engineering Reference
In-Depth Information
CHAPTER 5
Hydraulic Reliability Diagram
and Network Buffer Index as Indicators
The research presented in this chapter aims at alternative way of expressing network
reliability index, which has been derived from a diagram named the
hydraulic reliability
diagram
(HRD). This diagram shows the correlation between the pipe flows under regular
supply conditions and the loss of demand caused by the pipe failure. The reliability index
calculated from the position of all the dots on the graph, and also adding proportional
weighting to the pipes carrying variable flows, has been named the
network buffer index
(NBI). In this way, the NBI quantifies the HRD that clearly shows the pipes that are major
contributors to the loss of demand. Moreover, the HRD hints the network buffer for particular
level of demand. The concept has been illustrated on the networks of different degree of
complexity and the NBI has been compared with two other indices from the literature: the
resilience index of Todini (2000) and the network resilience defined by Prasad and Park
(2004). The results show clear correlation between all three indices, but the NBI evaluates
network reliability more realistically being more sensitive towards the change of network
configuration than the resilience indices that are predominantly influenced by energy balance
in the network.
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