Model for evaluating networks under correlated uncertainty: netcor

Construction activities are often influenced by factors such as weather, labor, and site conditions. When several activities are influenced by the same factor, their durations may be correlated. If many activities along a path are correlated, the variability of path duration will increase, possibly increasing the uncertainty of completing the project by a target date. This paper presents the simulation-based model NETCOR (NETworks under CORrelated uncertainty) to evaluate schedule networks when activity durations are correlated. Based on qualitative estimates of the sensitivity of each activity to each factor, uncertainty in an activity's duration distribution (grandparent) is distributed to several factor subdistributions (parents). Each subdistribution is broken down further into a family of distributions (children), with each child corresponding to a factor condition. Correlation is captured by sampling from the same-condition child distributions for a given iteration of the simulation. NETCOR integrates the effect due to each factor at the path level. Awareness of the factors to which a path is sensitive can provide management with a better sense of what to control on each path, particularly on large projects.