Logic-Based Benders for intermodal operations with delay penalties Ioannis Avgerinos1 Ioannis Mourtos1 and Georgios Zois1 1ELTRUN Lab Department of Management Science and Technology Athens University of Economics and Business

2025-04-24 0 0 817.3KB 26 页 10玖币
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Logic-Based Benders for intermodal operations with delay penalties
Ioannis Avgerinos1,*, Ioannis Mourtos1, and Georgios Zois1
1ELTRUN Lab, Department of Management Science and Technology, Athens University of Economics and Business,
Patision 76, 10434, Athens, Greece E-mail: iavgerinos@aueb.gr, mourtos@aueb.gr, georzois@aueb.gr
*Corresponding Author
Abstract
Intermodal logistics typically include the successive stages of intermodal shipment and last-mile delivery.
We investigate this problem under a novel Logic-Based Benders Decomposition, which exploits the staged
nature of the problem to minimise the sum of transport costs and delivery penalties. We establish the
validity of our decomposition and apply effective optimality cuts. Apart from models and formal proofs, we
provide extensive experimentation on random instances of considerable scale that shows the improvement
achieved in terms of small gaps and shorter time compared to a monolithic MILP approach. Last, we propose
a major extension of our generic method for a real logistics case. The implementation of the extension on
real instances show the versatility of our method in terms of supporting different planning approaches thus
leading to actual cost improvements.
Keywords. Logistics, Benders decomposition, intermodal transportation.
1 Overview and Background
The operation of functional distribution networks remains a major challenge in freight transportation, as in-
dicated also by the COVID-19 outbreak, which required acute response to severe disruptions. A report of
the International Finance Corporation of the World Bank Group [20] lists the closure of the borders between
Germany and Poland and the shortage of truck drivers in India as two events that challenged the endurance
of the logistics’ providers. The increase of railway freight transports, as a response to the radical decrease of
air freight capacity between China and Europe during the pandemic [20], shows that using alternative modes
of transport could tackle such challenges. In parallel, Direct Supply Chains [28] aim at dynamically shaping
Supplier - Organization - Customer routes that minimize both the operating costs and the delayed deliveries.
As the last-mile stage of the chain, in which the delay penalties are involved, is determined by the intermodal
transports of the preceding middle-mile stage, a proper coordination between these two stages is required.
In this study, we aim at minimizing the total transportation costs and delivery penalties of a logistics supply
chain by an exact optimization method that finds provably near-optimal solutions in realistically-sized instances
in reasonable time. For that to happen, the intermodal transportation and the last-mile deliveries must be si-
multaneously planned as heavier transport costs occur in the former stage, whereas delays are realised in the
latter. A Mixed-Integer Linear Programming (MILP) model is intractable for a commercial Integer Program-
ming solver and this is where our technical contribution comes forward. That is, we propose a Logic-Based
Benders’ decomposition (LBBD) [18, 19] of the two-staged problem, motivated by the recent LBBD literature
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arXiv:2210.05592v1 [math.OC] 11 Oct 2022
on supply chain problems (e.g., [3, 36]). In our LBBD, the so-called master problem handles the intermodal
transportation problem, whereas a set of subproblems handles the last-mile delivery. Further aspects of interest
include the introduction of appropriate optimality cuts plus subproblems’ relaxation and valid inequalities, all
aiming at strengthening the master problem’s formulation. In particular, inspired by a modern concept of de-
composition schemes, namely Partial Benders decomposition, we retain information of the subproblems to the
master problem, so that a faster convergence is achieved.
Relevant Background. Cross-docking is a logistics concept which includes consolidation points for the
orders, as intermediate stations between the supplying points and the customers. A comparison of the cost-
effectiveness of Cross-Docking and the regular direct-shipment policy is provided by [31], and a model that
combines both approaches is described by [7]. Since Cross-Docking operations occur in our setting, we draw
ideas from [40, 32]. An extended survey on the inclusion of intermediate facilities in freight transport networks
appears in [17]. If the network includes multiple Cross-Docking stations, the multi-depot Location-Routing
problem of [39] and the multi-depot VRPTW of [24] would be of value.
Intermodal networks have long been studied under an optimisation viewpoint [26]. This is not surprising
because they include several alternative topologies [38] and network designs. Notably, our work considers a
hub-and-spoke layout, that is the direct shipment of orders from hubs to customers. In addition to the selection
of the means of transport that will perform the shipment, a logistics supply chain must also consider the delays
of the deliveries: indicatively [21] considers fixed arrival rates and transport times to compute the delays of
the deliveries in a USA road-rail intermodal network. An intermodal network typically includes timetabled
transport services of different modes (rail or ship), in which each service can be performed during multiple
time windows in a planning horizon. As this is also the case in our study, we extend the approach of [29]
that constructs identical copies of transport services that depart in different time instances. Time aspects are
important also for the hub location problem in an intermodal network [4].
Recently, [15] offer a heuristic for transferring hazardous materials through a network of railway or roadway
nodes, thus solving a routing problem under stochastic scenarios. [12] aim to connect inland hubs with ports
through a network under strict time windows, so that a set of containers is shipped by the sea terminals. While
the model of [12] considers containers that are already loaded, the study of [25] includes hubs that are also
charged with the consolidation of orders to vehicles before the latter are routed through a multi-modal network.
All three studies examine realistic instances that are significantly larger than the ones previously examined in
the literature. Therefore, these papers suggest heuristic methods, since a commercial solver cannot respond
in reasonable time. We are quite motivated by these developments, as our approach can handle instances of
analogous size and of broader scope.
The literature on intermodal transportation is enormous, yet the one summarized in Table 1 shows the use of
multiple optimization methods. Although heuristic methods remain of great value, the contemporary landscape
reveals that 3PL provider compete on total cost, thus finding the optimal solution matters. Exact methods are
known to be slow or inappropriate in terms of memory requirements, thus our work exploit the staged nature of
our problem to apply a decomposition scheme. Decomposition-based methods are widely used in transportation
problems, some of them being intermodal [14, 16]. The main framework of our exact approach for this paper
will be Benders Decomposition [9] and, in fact, its logic-based extension [18] (LBBD). The closest study relying
on LBBD is [27], although LBBD has broad applicability [33]. Beyond modelling, the implementation of LBBD
is a non-trivial task as its success depends on the integration of valid cuts and also the combination of MILP
and Constraint Programming (CP) formulations, as nicely discussed in [22]. Recently, the concept of Partial
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Reference Description Solution Approach
Wu et al., 2002 [39] Multi-depot Vehicle Routing Problem Heuristic, TS
Rousseau et al., 2004 [26] Vehicle Routing Problem with Time Windows CG, CP
Moccia et al., 2011 [29] Intermodal Transportation Problem CG, BnC
Alumur et al., 2012 [4] Intermodal Hub Location Problem MIP
Ishfaq & Sox, 2012 [21] Intermodal Network Design Heuristic, TS
Li et al., 2014 [24] Multi-depot Vehicle Routing Problem GA, LS
Ghane-Ezabadi & Vergara, 2016 [16] Intermodal Network Design Decomposition
Yu et al., 2016 [40] Vehicle Routing Problem with Cross-Docking MIP, SA
Nikolopoulou et al., 2017 [31] Cross-Docking and Direct Shipment Comparison LS
Wang & Meng, 2017 [37] Intermodal Network Design Nonlinear Algorithm, BnB
Ghaderi & Burdett, 2019 [15] Intermodal Transportation Problem Heuristic
Mah´eo et al., 2019 [27] Transit Network Design BD
Azizi & Hu, 2020 [7] Pickup and Delivery Problem with Location Routing MIP, BD
Belieres et al., 2020 [8] Logistics Network Design BD
Fazi et al., 2020 [12] Pickup and Delivery Problem with Location Routing Heuristic, TS
Avgerinos et al., 2021 [6] Intermodal Transportation Problem BD
Fontaine et al., 2021 [14] Intermodal Transportation Problem BD
Li et al., 2021 [25] Intermodal Transportation Problem Heuristic
Qiu et al., 2021 [32] Vehicle Routing Problem with Cross-Docking BnC
TS Tabu Search
CG Column Generation
CP Constraint Programming
BnC Branch-and-Cut
BnP Branch-and-Price
MIP Mixed Integer Problem
LS Local Search
GA Genetic Algorithm
SA Simulated Annealing
BnB Branch-and-Bound
BD Benders Decomposition
Table 1: Summary of literature on Routing and Intermodal Transportation Problems
Benders Decomposition, that is addition of information derived from the subproblem to strengthen the master
problem, has been implemented on stochastic network design problems [10]. As [8] and [14] also did for their
presented logistics network design problems, we implement this idea on our decomposition setting.
Our contribution. To the best of our knowledge, this is the first paper offering an exact approach that
considers together the intermodal transportation stage and the last-mile delivery of a Direct Supply Chain.
Unifying these two stages allows us to consider the delayed delivery penalties, which are significantly determined
by the preceding intermodal transportation, but nevertheless charged during the last-mile delivery.
From an application-oriented standpoint, we experiment with large-scale randomly generated instances,
with 60 160 orders. These orders are transferred through a network of 7 hubs, connected with hundreds of
intermodal services. Let us note that [16] solve instances of 150 orders, consolidated in 4 hubs and transferred
by combinations of 3 modes per connected pair of hubs, while [25] address the shipment of 300 orders to a
network of 20 nodes; [12] consider datasets of 600 containers, nevertheless their network is unimodal. Thus, our
instances are comparable with the largest in the intermodal transportation literature. In addition, we expand
the scope of the typical intermodal network planning problem, by considering penalties of delays in the objective
function.
To evaluate the efficiency of our method under the additional complications imposed by a real-life application,
we extend our formulations to an actual case of a 3PL provider in Europe. This case integrates all three stages
of a logistics supply chain (i.e., first-mile,middle-mile,last-mile). For the last-mile stage, two alternative
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configurations are used. Our method exploits the fact that the practical restrictions of the problem allow us
to pre-compute fixed routes for the first and last-mile stages, thus modelling the corresponding vehicle routing
problems as exact-covering or resource-constrained scheduling problems. The extended LBBD algorithm is
evaluated, after being implemented on real instances, given by the logistics provider. This paper is a strongly
enhanced generalisation of [6], whose experiments on smaller instances show already that a commercial solver
cannot handle the entire problem thus making the decomposition necessary.
2 Problem definition and notation
2.1 Problem definition
Let Ibe the set of nodes of an intermodal network. Subset JIincludes the Distribution Centers hubs (DC
hubs), in which orders Nare consolidated into loading compartments G. Each compartment is dedicated to one
DC hub, hence set Gis divided into subsets Gj, j J. Subset LIincludes Satellite hubs, in which orders are
brought to before their final destination. The rest of the nodes of set I, namely intermediate hubs, are labelled
as KI.
After the completion of the consolidation process, all loaded compartments must be shipped to any Satellite
hub lL, via an intermodal services network. We consider three transport modes (i.e., roadway, railway, and
seaway modes) and a set of scheduled transport services, denoted by S. Each service sSis featured with an
origin node originsI, a destination node destsI, a fixed time of departure and arrival (departuresand
arrivalsrespectively), a variable cost ctravel
s, which is charged for each compartment that is shipped by service
s, a fixed cost cf ixed
s, and a capacity (in number of compartments) Qs. For each node iI, we distinguish
the services arriving in and departing from it, by introducing the sets δ(i) and δ+(i), respectively. Last, each
service is linked with a subset of invalid co-assignments FsS, that is the set of services that cannot be added
in the same intermodal route with s. Each subset Fsincludes all services pS\ {s}that:
a. depart or arrive during service s(i.e., departuresdeparturep< arrivalsor departures< arrivalp
arrivals),
b. start from the destination of sbefore the completion of s(i.e., originp=destsand departurep< arrivals),
or
c. arrive to the origin of slater than the departure of s(i.e., destp=originsand arrivalp> departures).
The solution of the intermodal transportation stage is a set of combined services, that start from a DC hub and
terminate to a Satellite hub. Each service is linked with a set of assigned compartments. Note that, despite the
dedication of each order or compartment to a DC hub, there are no pre-assignments to Satellite hubs, hence each
loaded compartment could be transferred to any Satellite hub by eligible services, regardless of its components.
As the problem requires the assignment of loaded compartments to services of different capacity and cost,
the intermodal transportation stage is structured as a Generalized Assignment Problem, which is known to be
NP-hard [13]. The complexity arises from orders being loaded to compartments, which must then be transferred
through the intermodal network at a minimum ‘flow’ cost.
Concerning now the last-mile stage, each order nNis featured with a deadline tnand a value of weight
wn, which is related with the importance of the order. The deadlines are not strict, nevertheless their violation
implies a penalty cost, equal with the number of days of delayed delivery, multiplied by the weight value of the
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order. To comply with the properties of hub-and-spoke networks, in which all orders are delivered in a single
route, we consider a TSP for each used service s∈ {S|destinationsL}, starting from destsLand traversing
through the delivery points of all orders that were shipped by service s.
As the objective function of each TSP includes the total transportation costs and the delay penalties, the
last-mile stage is structured as a set of multiple Single-Machine Scheduling Problems with sequence-dependent
times, aiming to minimize the total weighted tardiness, which are known to be strongly NP-hard [23].
An illustrative example of the intermodal network, the available services that connect the hubs, and the
processes that are conducted in each stage of the problem is presented in Figure 1.
Figure 1: A sketch of our network
2.2 Mathematical Model
Let Pbe an MILP formulation for the unified optimization problem that was described above. Parameters and
variables of Pare as in Table 2.
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摘要:

Logic-BasedBendersforintermodaloperationswithdelaypenaltiesIoannisAvgerinos1,*,IoannisMourtos1,andGeorgiosZois11ELTRUNLab,DepartmentofManagementScienceandTechnology,AthensUniversityofEconomicsandBusiness,Patision76,10434,Athens,GreeceE-mail:iavgerinos@aueb.gr,mourtos@aueb.gr,georzois@aueb.gr*Corresp...

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