Seismic retrofit optimization of water distribution systems based on the reduction of uncertain damage scenarios

Pre-event interventions, such as retrofit of critical components, are effective strategies to improve the seismic performance and resilience of infrastructure systems. This paper proposes a damage scenario reduction method aims to reduce the computation burden within the seismic retrofit optimization for water distribution systems (WDSs) considering the uncertain damages of pipelines. The optimization framework consists of a multi-objective optimization model for WDS pipeline retrofit and a sequential optimization model for the reduction of uncertain damage scenarios. The multi-objective optimization model is established to minimize the retrofit cost and maximize the seismic performance of WDS. The sequential optimization model, namely weighted optimization-based probabilistic scenarios (OPS + W), was designed to mitigate the computational burden of the multi-objective optimization model, which arises from considering pipeline damage uncertainties through quasi-Monte Carlo (QMC) sampling that generates numerous damage scenarios. The OPS + W selects a few representative damage scenarios from numerous QMC scenarios, aiming to minimize the error of pipeline damage probabilities counted by the representative scenarios, where the error is weighted by the importance of pipeline. The effectiveness of OPS + W is verified through its application in seismic retrofit optimization of two WDS cases and compared with other scenario reduction methods. Application results reveal that the retrofit strategies derived from OPS + W have the highest similarity to those obtained from QMC scenarios while requiring only 3 %–10 % of the computation time compared to using QMC scenarios.