Project management under uncertainty: A mixed approach using flexible resource management to exploit schedule flexibility
João Faria · Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) · 2016
Project management involves onetime endeavours which demand for getting it right the first time. Also, project scheduling, being one of the most modelled project management process stages, still faces a wide gap separating theory from practice. Demanding computational models, and their consequent call for simplification, divert the implementation of such models in project management tools from the actual day to day project management process. Special focus is being made to the robustness of the generated project schedules facing the omnipresence of uncertainty. An "easy" way out is to add, more or less cleverly calculated, time buffers that always result in project duration increase and correspondingly, in increased costs. A better approach to deal with uncertainty can be to explore slack that might exist in a given project schedule, even more when a non-optimal schedule is used, which is what usually happens in practice. The combination of such approach with recent advances in modelling resource allocation and scheduling techniques, to cope with the increasing flexibility in resources, is a promising line of research, in order to generate more adequate project management tools. "Flexible resource profiles Resource Constraint Project Scheduling Problem" (FRCPSP) formulations are a step in this direction but a distinct approach can be followed, considering that, apart from being flexibly allocated or not, resources are themselves flexible by nature. More specifically, when renewable resources are considered, their capacity to perform work in a time unit (e.g. a day), which is considered to be one unit for each resource in traditional models, can be increased so that they can perform additional work in a time unit, or it can be decreased with the consequent reduction on the performed work. In reality, this flexibility is frequently considered by project managers. The objective here is to use this possibility so that, when combined with the slack that some activities have in a specific schedule, deviations that might occur during a project's execution can be absorbed. In the most critical case, in which a critical activity (activity without slack) will have its duration increased, the strategy is basically to slow down non-critical activities (activities with slack), by putting their resources in a decreased work mode, so that the critical activity, which is about to have an increase in its duration delaying the whole project, can still be executed within time by using resources in an increased working mode. This thesis analyses this combination, its consequences and limitations and proposes models to generate and enhance starting (baseline) schedules that can take a greater advantage of this approach.