The design of an activity buffer that minimises project delay

Abstract

The theory of constraint (TOC) has long been applied to planning project schedules, and critical chain and buffer management are both developed to reduce the impact of future project uncertainties. Several models are proposed for the project activity buffers, including: 1) the cut and paste method proposed by Goldratt, in 1997; 2) the square root error method proposed by Newbold, in 1998; 3) the adaptive procedure with density proposed by Tukel in 2005. This study proposes a multi-objective mathematical programming model that enables project managers to concurrently maximise the on time delivery of project activities. The multi-objective model is consolidated into a single-objective programming model using a fuzzy membership function. Maximising the value of this membership function leads to the maximisation of the probability of on time completion for all project activities. The model is applied to a real case and the result shows that the proposed fuzzy model determines the duration of activities, which ensures that a project can be completed with the highest probability compared to other methods.