Project Scheduling by Integration of Time Cost Trade-off and Constrained Resource Scheduling

Abstract

Project managers today rely on scheduling tools based on project network techniques like Critical Path Method (CPM) to determine the overall project duration and the activities float time. Such data provide important information about the degree of flexibility with respect to the project schedule that leads to greater efficiency in planning and control of projects. The traditional representation of CPM, however, is based on two unrealistic assumptions: that the project deadline is not restricted and that resources are unlimited. In most of the construction projects the deadline and resource limits are practical constraints that need to be satisfied simultaneously. While the available literatures describe several techniques to resolve the Time Cost Trade off (TCT) and Constrained Resource Scheduling (CRS) individually, little effort has been devoted to consider them simultaneously because of the higher modeling complexity involved. No commercial software includes any TCT heuristic to help meet deadline, let alone any procedure to resolve both deadline and resource constraints. In practice on the other hand there is a need to formulate a method that simultaneously resolves to meet out the specified duration and resource constraints. This paper therefore introduces a two-step procedure where first the TCT is applied using Microsoft excel software to meet the project deadline assuming unlimited resources. The various feasible schedules obtained in the first step are then explored by applying CRS using Microsoft Project Software (MSP) to arrive at the desired project schedule meeting the deadline with available resources. The proposed approach was experimented on several case studies that proved its usefulness. The intertwined approach using simple and popular Microsoft office tools (Excel and MSP) is logical, fast and provides a set of feasible project schedule meeting the deadline and that do not violate resource limits.