Multi-step optimization of logistics networks : strategic, tactical, and operational decisions

In every-day life, people and goods have to be transported from one place to another by different kinds of resources, e.g. buses, trains, airplanes and ships, but also transport belts, cranes, elevators and robots. A group of these resources linked together with the purpose of transporting people and/or goods from one place to the other forms a logistics network. Such a network is usually run by a number of logistics providers, some of which control the links while others control the nodes of that network. Each provider faces the problem of delivering the right amount of items in the right place at the right time. To satisfy these goals at minimal costs, a provider has to make combined decisions at three levels: strategic, tactical and operational. Due to the ever-growing complexity of the combined decisions, more often a provider requires efficient decision tools (mathematical models) that solve the problems for him. During the last decades, the number of people and goods to be transported has grown that large that even intelligent decision support tools cannot solve the combined decisions at once. A possible approach is to separate the overall problem into several subproblems, which are then solved step by step, or if possible alternatingly. In this dissertation we propose, develop and test multi-step optimization methods to support logistics providers in their decision making process in two particular logistics networks: i) a distribution network and ii) a multi-terminal container operation as node in a network. The separation of the combined problems into several subproblems is chosen such that each individual subproblem is practically interesting in its own right and can be solved within the time allowed at the considered decision making level(s). Although existing theoretical studies have already investigated several parts of the considered logistics networks, the separations chosen in this dissertation are unique and result from specific problems faced in practice. The research in this dissertation is supported by the Koninklijke Frans Maas Groep (taken over by DSV) and the terminal operator PSA HNN in Antwerp Belgium, who both provided us with interesting, practical problems and data to test our methods. The study concerning the distribution network discusses the joint problem at the tactical and operational level faced by a third party logistics services provider. The objective is to construct a consistent and efficient network topology (i.e. where to establish line hauls between suppliers, warehouses and retailers), that still enables just in time delivery at the operational level. A procedure is proposed that iteratively deletes network line hauls based on the operational performance of the present topology. An extensive number of experiments suggest that the proposed alternating procedure is very fast and finds quite accurate solutions. As expected, the constructed network topology is sensitive to the averages of supply and demand. Interestingly, the constructed network topology appears to be robust to changes in second and higher orders of supply and demand distributions. With respect to the multi-terminal container operation, we consider one terminal operator, who is responsible for multiple terminals in one container port. The combined problems at strategic, tactical and operational levels in this multi-terminal container operation are separated into four main problems. The first subproblem investigates whether the same number of vessel lines can be operated with a smaller amount of crane capacity and at the same time the amount of container transport between the different terminals can be reduced. The proposed approach aims to spread the vessels over the terminals and over time such that the workload is balanced and the inter-terminal transport is minimized. Although we guarantee that quay and crane capacities are never exceeded, the specific berth positions and crane allocations are still to be determined. Results of a case study in a representative data set suggest that a significant amount of crane capacity can be saved and at the same time the amount of inter-terminal transport can substantially be reduced. Once the various vessel lines have been allocated to a terminal for a certain amount of time, the second subproblem is to construct a refined schedule per terminal, which is robust to disturbances on vessel arrivals. In our definition a schedule is robust if for all arrival scenarios within an arrival window, feasible solutions exist and the maximally required crane capacity in the worst case scenario is minimal. A window-based model is proposed that allows slight modifications in the allocations from the first subproblem to increase the robustness of the terminals’ schedules. Again, we allocate quay and quay crane capacities, while the specific berth positions and crane allocations are not constructed yet. As expected, the window-based plan requires slightly more crane capacity than the nominal window-ignoring plan for zero or relatively small arrival disturbances. However, the window-based plan is much more robust to larger realistic disturbances that are still within the arrival window bounds. Given the schedules, the third subproblem allocates berth positions for the vessel lines at the quay and stack positions for the containers in the yard. These combined decisions determine the total travel distance, that has to be covered by straddle carriers moving containers from quay to yard and vice versa. A procedure is developed that alternatingly allocates i) berth positions, guaranteeing non-overlapping and ii) container blocks, ensuring that block capacities are never exceeded, such that the total straddle carrier distance is minimized. The alternating procedure appears to be very fast, but the result heavily depends on the initial condition. A second model is proposed that turns out to find a proper initial guess for the alternating procedure. Results suggest that the straddle carrier distance in a representative allocation can significantly be reduced by applying the proposed method. Recently, results of this procedure have been implemented in a terminal operated by PSA HNN. The results of the first three subproblems construct tactical schedules, berth positions and yard design. The fourth subproblem addresses the online operational decision making if the system is disrupted from this tactical timetable. A rolling horizon approach is proposed that takes forecasts on arrivals, load compositions and resource activities into account to construct decisions on the current operations. Subsequently, the vessels’ i) time allocation, ii) berth position allocation, and iii) crane allocation under disturbances are addressed. The three subproblems can be solved within the time allowed at this operational level. Experiments suggest that explicitly taking the forecasts of specific parameters into account can substantially reduce the operational costs. Hence, we think the proposed procedure can properly serve as a decision support tool for a terminal operator. This research clearly shows that the proposed methods can be very valuable for logistics providers. The actual implementation of one of the results into a terminal operated by PSA HNN is already a confirmation of the method’s suitability. Although the approaches in this dissertation may not take all specific managerial decisions into account, at least we are able to quantify the additional costs induced by these decisions

Data for OR spectrum paper simultaneous Berth allocation and yard planning at tactical level

A gzipped-tar file containing the files we used for generating the result in our 2013 paper: M.P.M. Hendriks, E. Lefeber, J.T. Udding, Simultaneous berth allocation and yard planning at tactical level, OR Spectrum 35(2), 441-456, 2013

Simultaneous berth allocation and yard planning at tactical level

We present a simultaneous berth allocation and yard planning problem at tactical level, since the berth allocation has a great impact on the yard planning and vice versa. This problem is solved by means of an alternating berth and yard planning heuristic approach. The alternating heuristic quickly converges to a local minimum which heavily depends on the starting point. Therefore, we formulate another optimization problem for generating a suitable starting point. A real size case study provided by PSA Antwerp shows that our approach to simultaneously solve both problems might reduce the total straddle carrier travel distance considerably as compared with a representative allocation

Robust periodic berth planning of container vessels

We consider a container operator, who serves a number of shipping lines by discharging and loading their periodically arriving container vessels. Disruptions on vessels’ travel times lead to stochastic arrivals in the port. To cope with these disturbances, the operator and each vessel line agree on two types of arrivals: arrivals i) within, and ii) out of a so-called arrival window. If a vessel arrives within its window, the operator guarantees a maximal process time. If not, the operator is not bound to any guaranteed process time. The problem is to construct a periodic window-based i) arrival, ii) departure and iii) time-variant crane capacity plan to minimize the maximal crane capacity reservation. In this paper, we propose a mixed integer linear program (MILP) that minimizes the maximal crane capacity reservation while window agreements are satisfied for all scenarios in which vessels arrive within their windows. Results of a case study suggest that with slight modifications to an existing plan, significant reductions in the maximal crane capacity reservation can be achieved. As a particular case, the MILP determines the conventional optimal window-ignoring plan. Results suggest that although the windowignoring plan on itself requires less crane capacity than the window-based plan, it is much more sensitive to the arrival window agreements

Online disruption management of container terminal operations

Abstract only

Strategic allocation of cyclically arriving container vessels to inter-related terminals

We consider a port consisting of a cluster of inter-related terminals, where container vessels arrive cyclically. The problem is to strategically assign a terminal and a time interval of berthing to each of the vessels in the cycle. Restricting properties are terminal quay lengths and quay crane capacity. Conflicting objectives are i) minimizing the number of required quay cranes, ii) minimizing the amount of inter-terminal traffic and iii) minimizing the total weighted deviation from desired berthing intervals. We formulate both a straightforward and an alternative mixed integer linear program to model this system. Results show that the alternative model is much faster solvable and enables to optimize real-life problems within a couple of hours

Strategic terminal allocation and time scheduling of cyclically arriving container vessels

We present an MILP formulation to construct a strategic, cyclic terminal allocation and time scheduling for a set of container vessels, which are processed by a multi-terminal port operator. Our case study is about balancing the workload over time, minimizing inter-terminal transport and minimizing deviations from the existing time schedule

Strategic allocation of cyclically calling vessels for multi-terminal container operators

We consider a terminal operator who provides container handling services at multiple terminals within the same port. In this setting, the well-known berth allocation problem can no longer be considered for each terminal in isolation since vessel calls should be spread over the various terminals to avoid peaks and troughs in quay crane utilization, and an allocation of two connecting vessels to different terminals will generate inter-terminal container transport. In this paper, we address the problem of spreading a set of cyclically calling vessels over the various terminals and allocating a berthing and departure time to each of them. The objectives are (1) to balance the quay crane workload over the terminals and over time and (2) to minimize the amount of inter-terminal container transport. We develop a solution approach based on mixed-integer programming that allows to solve real-life instances of the problem within satisfactory time. Additionally, a practical case study is presented based on data from the terminal operator PSA Antwerp who operates multiple terminals in the port of Antwerp, Belgium. The computational results show the cost of the currently agreed schedules, and that relatively small modifications can significantly reduce the required crane capacities and inter-terminal transport

End-of-life treatment decisions in nursing home residents dying with dementia in the Netherlands

Objective: The objective was to describe end-of-life treatment decisions for patients dying with dementia in various stages of dementia in long-term care facilities in the Netherlands with elderly care physicians responsible for treatment and care. Methods: We present data collected in the nationally representative Dutch End of Life in Dementia study (2007–2011). Within 2 weeks after death, 103 physicians completed questionnaires about the last phase of life in 330 residents with dementia who resided in 1 of 34 participating long-term care facilities. We used descriptive statistics. Results: Advance directives were rare (4.9%). A minority was hospitalized (8.0%) in the last month (mainly for fractures) or received antibiotics (24.2%) in the last week (mainly for pneumonia). Four residents received tube feeding or rehydration therapy in the last week. In almost half of the residents (42.3%), decisions were made not to start potentially life-prolonging treatment such as hospital transfer and artificial nutrition and hydration. In more than half of the residents (53.7%), decisions were made to withdraw potentially life-prolonging treatment such as artificial nutrition and hydration and medication. Antibiotics were more frequently prescribed for residents with less advanced dementia, but otherwise there were no differences in treatment decisions between residents with advanced and less advanced dementia. Conclusions: Physicians often withhold potentially burdensome life-prolonging treatment in nursing home residents in all stages of dementia in the Netherlands. This suggests that the physicians feel that a palliative care approach is appropriate at the end of life in dementia in long-term care