A two-stage approach for the critical chain project rescheduling

Abstract

The fundamental principle of critical chain project management is to use the critical chain instead of a traditional critical path, to insert a project buffer at the end of the project and to insert feeding buffers wherever non-critical chains join the critical chain to protect a timely project completion. Due to the complexity of project, inserting feeding buffers may cause a conflict, such as precedence conflict or resource conflict, which can be solved by rescheduling. However, after rescheduling some new problems may arise: non-critical chain may start earlier than critical chain (non-critical chain overflow), or a gap may occur between activities on the critical chain (critical chain break-down). This paper is aiming to solve these new problems by a two-stage approach combined with feeding buffer for rescheduling. In the first stage, a first-stage rescheduling based on priority rules together with a backward-recursive procedure is proposed for rescheduling to solve resource and precedence conflicts, resulting in a critical chain break-down or a non-critical chain overflow. In the second stage, a second-stage rescheduling based on a heuristic algorithm is proposed to eliminate new problems and generate a better rescheduling scheme. Finally, we do simulations on the 110 Patterson instances set to verify the feasibility, effectiveness and applicability of our two-stage approach for rescheduling. Simulation results show that, it is an effective approach to generate reliable rescheduling schemes in most projects with excellent performances, i.e. the average project length, timely project completion probability and etc.