Buffer sizing approach with dependence assumption between activities in critical chain scheduling

Improved critical chain buffer management framework considering resource costs and schedule stability

“…To model the random activity durations we use a right-skewed lognormal distribution with mean equal to the baseline duration and a coefficient of variation, cv, to represent the uncertainty level. A lognormal distribution has also been employed in a number of research articles on CC/BM (Tukel et al 2006;Bie et al 2012;Zhang et al 2015c). We would like to note that illustrating how to capture the duration uncertainty is beyond the scope of the present work.…”

“…A PB is added to the end of the critical chain in order to protect due date performance from variations in the durations of the critical activities. FBs are placed whenever a non-critical chain joins the critical chain in order to protect the critical chain from potential delays caused by the feeding paths (Bie et al 2012). Besides, the resource buffers are introduced in the form of an advance warning and are placed before any critical chain activity whose critical predecessor uses a different resource type.…”

Project buffer sizing of a critical chain based on comprehensive resource tightness

“…This method takes half of the estimated time as the average time of the activities, half of the safety sum cut from the critical chain as a project buffer, and half of the safety sum cut from the non-critical chain as a feeding buffer. However, considering 50% of the critical chain length as a project buffer may cause the project buffer to be too long, which will lead to a waste of resources and the loss of business opportunities (Bie, Cui, & Zhang, 2012;Herroelen & Leus, 2001). What is more, based on the property that project activity time obeys logarithmic normal distribution, Ashtiani, Jalali, Aryanezhad, and Makui (2007) use a mathematical statistics method to study the buffer size, and reach the conclusion that Goldratt's 50% buffer size method leads to serious waste.…”

A New Buffer Monitoring Approach Based on Earned Value Management Concepts

“…Other researchers focused on different aspects of project and organizations and considered other conditions affected on the size of buffers. A detailed study of this section is outside the scope of this paper and readers can refer to some researches, for example, [21], [2] and [9].…”