Time-cost-quality tradeoff problem solving with genetic algorithm

Abstract

Based on solving one of the multi-objective problems of construction in project management, this paper aims to conclude a series of new practical comprehensive mathematical models to solve the time-cost-quality tradeoff problem in construction engineering. With reviews of previous studies, some methodologies are selected with their merits to consist of individual equation between time-cost and time-quality and one intergradient objective function combining these three elements together. Critical Path Method (CPM) is applied to sum up the total time for project construction; Work Breakdown Theory (WBT) dividing the total cost into each individual activities with their own direct, indirect and tardiness cost; a new indicator as Quality Performance Index (QPI) is proposed to qualify the project quality. Moreover, in order to achieve the optimization of these three elements, Minimize Ratio Method (MRM) is added to compromise them into one objective function. Only if the minimum value of this function is founded, the corresponded value of the time could be marked as the optimal solution, as well as the indicated cost and quality. By applying Genetic Algorithm (GA) to optimize proposed objective function, two cases were studied in order to identify and verify their applicability and practicability. One of them is a relative small office building consists of 19 activities, and the other is a large civil engineering of offshore wind-generated power project that contains 104 activities and still in progress. After the optimization of two cases, the optimal results present a better quality, shorter duration of construction time but a little bit higher cost in terms of equal priority among construction time, cost and quality.