Flexible model for time/cost tradeoff problem

This paper presents a flexible mixed integer-programming model for the solution of the time/cost tradeoff problem encountered in project management. Whereas it is commonly assumed that the time/cost function is linear, the model presented in this paper makes minimal assumptions and accommodates any type of cost function that is linear, piecewise linear or discrete. The model can be used for answering various "what if" questions that may be very helpful to a project manager in making rational decisions. The basic model minimizes the total cost which is the sum of direct and indirect costs, subject to a project deadline constraint. A simple modification in the model changes the focus from minimizing total cost to minimizing project completion time subject to a resource constraint. The models of this paper can be set up and run very easily on commercially available optimization packages with an integer-programming module. These models provide a viable alternative to more specialized algorithms developed for the time/cost tradeoff problem simply because a typical project manager may not have the necessary skills or resources to implement specialized algorithms.