Abstract
Most model based studies on project uncertainty investigate a single source of uncertainty, with a dominant focus on stochastic activity durations. However, another major uncertainty facing engineering projects is that of changes in design troughout the project delivery. This may come from uncertainty in the market, technology, or regulations, leading to changes in design and implementation paths, with alterations in the project network itself. This comes on top of stochastic and correlated activity durations for a given design. In this paper we develop a stochastic program to investigate how uncertainty in design and activity durations, together, affect planning, and their relationships. The findings suggest that when design uncertainty is modelled by multiple alternatives and delayed decisions on the final alternative, stochastic and correlated activity durations have limited impact. In situations with alternative and subtitutable solutions available for a given design, correlations drive a certain learning behaviour.
Highlights
This paper treats project uncertainty and planning decision making in construction and engineering projects, where frequent changes in the scope, outfitting, design and technical specifications are leading to operational adjustments throughout the project delivery
We add constraints connecting the same nodes of different copies of the tree, enforcing equal decision at the nodes as long as we have not learned the duration of the corresponding activity. These constraints are like the usual non-anticipativity con straints (NACs), except that they are being switched on and off by the decision variables; for this reason, we call them dynamic non-anticipativity constraints (DNACs)
Description progress of activity a ∈ A R at the end of (n, s) time spend working on a ∈ A R during period (n, s) time spend reverting/undoing a ∈ A R during period (n, s) has activity a ∈ A finished by the end of period (n, s)? is activity a ∈ A ongoing in per. (n, s)? amount of resource r at cost-level l used in per. (n, s) cumulative progress of a at the end of (n, s) indicator for DNAC constraints for a ∈ A s during (n, s)
Summary
This paper treats project uncertainty and planning decision making in construction and engineering projects, where frequent changes in the scope, outfitting, design and technical specifications (all related) are leading to operational adjustments throughout the project delivery. The authors show that managerial flexibility may be too costly to handle high operational uncertainty None of those models provide a systematic decision support framework, though, to help deepen insight into the relationships among the different sources of uncertainties. Nor do they handle critical modelling aspects, like the planning dynamics driven by information arrival, and correla tions, which we discuss . The purpose of our paper is to provide a model that helps investigating the combined impact of, and relationships between, design changes and stochastic activity durations, including correlations between these.
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