Time-cost optimization: Using GA and fuzzy sets theory for uncertainties in cost

Uncertainties should be considered in any time-cost trade-off problems when minimizing project cost and duration, which leads to the so-called stochastic time-cost trade-off problem. A new approach to investigate stochastic time-cost trade-off problems employing fuzzy logic theory is presented. The proposed approach fully embeds the fuzzy structure of the uncertainties in total direct cost into the model. An appropriate GA is used to develop a solution to the multi-objective fuzzy time cost model. The accepted risk level of the project manager is defined through α cut approach for which a separate Pareto front with set of non-dominated solutions has been developed. To compare the alternative set of options for any assumed project duration, associated fuzzy costs for different values of α cut are ranked employing two appropriate approaches for fuzzy costs comparison. The proposed models are applied to solve two benchmark test problems. It is shown that the models facilitate the decision-making process by selecting specified risk levels and employing the associated Pareto front.