Influences of regional site condition and grid size on seismic damage assessment of water distribution systems

In this study, the influences of regional site condition and grid size on the seismic damage assessment of water distribution systems (WDSs) are quantitatively examined. A water distribution system, termed M-WDS, is employed as the demonstrated system. With an assumed strike-slip linear fault in the vicinity of M-WDS, a number of spatially correlated peak ground velocity fields are realized for scenario earthquakes for each combination of grid size and regional site-condition parameter. Seismic damage analyses are then conducted for both scenario-based and probabilistic-based earthquake cases. Comparative results under scenario earthquakes indicate that increasing grid size notably increases the uncertainty of the seismic damage estimates of M-WDS, and such grid-size influence is more pronounced for more heterogeneous regional site conditions. It is also found that using a large grid size results in overestimated risk-based assessment for the probabilistic damage estimates of MWDS, and the annual rates of exceeding large numbers of damaged pipelines are higher as the regional site conditions become more homogeneous. Additional analyses are conducted to investigate such influences on the seismic damage assessment of large-city scale WDSs. The ratio of the grid area to the whole WDS area being 0.02 is generally recommended for choosing an appropriate grid size for WDSs with different scales. A further reduced grid size is recommended for study areas exhibiting heterogeneous regional site conditions.