Synchronised warehousing and transportation operations of export containers considering supply chain disruptions

When supply chain disruptions occur, shipping timetables often become uncontrollable due to shortages in logistics capacity and soaring freight rates. The daily planning and execution of manufacturers' warehouse and truck fleet operations become disrupted. The situations of 'products waiting for trucks' and 'trucks waiting for products' occur frequently. In this context, synchronised decisions involving loading bay allocation and truck fleet planning are particularly important for large manufacturers. This study proposes a novel synchronised warehousing and transportation problem for export containers, which is formulated as an assembly scheduling model of two-stage parallel machines. To reflect the problem's authenticity, four drop-and-pull transportation scenarios are implemented for a single truck. Decisions in the proposed model are made prior to a scheduling cycle and include order picking sequence, loading bay allocation, as well as task assignment and sequence for each truck. An effective population-based variable neighbourhood search method, complemented by a deadlock repair approach, is employed and validated through several numerical experiments. The results indicate that the total waiting time per order, when decisions on the warehouse and transportation sides are made independently, is reduced by more than 50% using the static synchronised mechanism. When considering perturbations in operation times caused by supply chain disruptions, this study proposes a dynamic synchronisation mechanism. Although a dynamic mechanism generally outperforms a static one under perturbations, we deserve that involving multiple reschedules may mitigate the positive interaction between different perturbations and increase operational costs. Therefore, the application of a synchronisation strategy should be tailored to the actual situation, considering the type and frequency of perturbations.