OPTIMIZATION MODELS AND METHODOLOGIES TO SUPPORT EMERGENCY PREPAREDNESS AND POST-DISASTER RESPONSE

This dissertation addresses three important optimization problems arising during the phases of pre-disaster emergency preparedness and post-disaster response in time-dependent, stochastic and dynamic environments. The first problem studied is the building evacuation problem with shared information (BEPSI), which seeks a set of evacuation routes and the assignment of evacuees to these routes with the minimum total evacuation time. The BEPSI incorporates the constraints of shared information in providing on-line instructions to evacuees and ensures that evacuees departing from an intermediate or source location at a mutual point in time receive common instructions. A mixed-integer linear program is formulated for the BEPSI and an exact technique based on Benders decomposition is proposed for its solution. Numerical experiments conducted on a mid-sized real-world example demonstrate the effectiveness of the proposed algorithm. The second problem addressed is the network resilience problem (NRP), involving an indicator of network resilience proposed to quantify the ability of a network to recover from randomly arising disruptions resulting from a disaster event. A stochastic, mixed integer program is proposed for quantifying network resilience and identifying the optimal post-event course of action to take. A solution technique based on concepts of Benders decomposition, column generation and Monte Carlo simulation is proposed. Experiments were conducted to illustrate the resilience concept and procedure for its measurement, and to assess the role of network topology in its magnitude. The last problem addressed is the urban search and rescue team deployment problem (USAR-TDP). The USAR-TDP seeks an optimal deployment of USAR teams to disaster sites, including the order of site visits, with the ultimate goal of maximizing the expected number of saved lives over the search and rescue period. A multistage stochastic program is proposed to capture problem uncertainty and dynamics. The solution technique involves the solution of a sequence of interrelated two-stage stochastic programs with recourse. A column generation-based technique is proposed for the solution of each problem instance arising as the start of each decision epoch over a time horizon. Numerical experiments conducted on an example of the 2010 Haiti earthquake are presented to illustrate the effectiveness of the proposed approach

The one container drayage problem with soft time windows

Intermodal freight transport consists of using different modes of transport without changing the load unit. This results in a significant reduction in the time that goods spend at intermodal terminals, where transshipment takes place. Drayage refers to the transport of freight on trucks among intermodal terminals, depots, customers and suppliers. In spite of the fact that drayage only represents between 5 and 10 percent of total distance, it may amount up to more than 30 percent of the total costs. The aim of this work is to study drayage operations. First, an extensive literature review is undertaken. Since the intermodal transport chain can become more efficient by means of a proper organisation of the drayage movements, the optimization of the daily drayage problem has been identified as one of the main ways of reducing the drayage cost and improving intermodal operations. On this problem, the lack of a common benchmark has hindered reaching further conclusions from all the research carried out. Therefore, this paper proposes a common framework and presents a generalized formulation of the problem, which allows modeling most drayage policies, with the limitation of only considering one-container problems. Results show that flexible tasks in the repositioning of empty containers as well as soft time windows can reduce the operating costs and facilitate the management of drayage companies. This work may help consider adequate policies regarding drayage operations in intermodal terminals

Sequence-Based Simulation-Optimization Framework With Application to Port Operations at Multimodal Container Terminals

It is evident in previous works that operations research and mathematical algorithms can provide optimal or near-optimal solutions, whereas simulation models can aid in predicting and studying the behavior of systems over time and monitor performance under stochastic and uncertain circumstances. Given the intensive computational effort that simulation optimization methods impose, especially for large and complex systems like container terminals, a favorable approach is to reduce the search space to decrease the amount of computation. A maritime port can consist of multiple terminals with specific functionalities and specialized equipment. A container terminal is one of several facilities in a port that involves numerous resources and entities. It is also where containers are stored and transported, making the container terminal a complex system. Problems such as berth allocation, quay and yard crane scheduling and assignment, storage yard layout configuration, container re-handling, customs and security, and risk analysis become particularly challenging. Discrete-event simulation (DES) models are typically developed for complex and stochastic systems such as container terminals to study their behavior under different scenarios and circumstances. Simulation-optimization methods have emerged as an approach to find optimal values for input variables that maximize certain output metric(s) of the simulation. Various traditional and nontraditional approaches of simulation-optimization continue to be used to aid in decision making. In this dissertation, a novel framework for simulation-optimization is developed, implemented, and validated to study the influence of using a sequence (ordering) of decision variables (resource levels) for simulation-based optimization in resource allocation problems. This approach aims to reduce the computational effort of optimizing large simulations by breaking the simulation-optimization problem into stages. Since container terminals are complex stochastic systems consisting of different areas with detailed and critical functions that may affect the output, a platform that accurately simulates such a system can be of significant analytical benefit. To implement and validate the developed framework, a large-scale complex container terminal discrete-event simulation model was developed and validated based on a real system and then used as a testing platform for various hypothesized algorithms studied in this work

Roll-on/roll-off terminals and truck freight : improving competitiveness in a motorways of the sea context

In recent years transport policy at an European Level has been focused on reducing the share of road transportation and promote alternative transportation means in order to reduce road congestion and carbon footprint. One of the solutions proposed has been promoting Short Sea Shipping (SSS) transportation combined with land transportation to become a door-to-door alternative to the monomodal road alternative. The maritime centered option would hit to birds with a stone: reduce congestion in the most urbanized areas of the European Union and partly replacing heavy polluting truck haulage for an environmentally friendlier option. The European Commission launched many polices and initiatives to make the modal shift happen, the crown jewel being the launch of multiple initiatives promoting the establishment of a system of Motorways of the Seas. Those are links between ports with higher standards in terms of travel time, costs and flexibility, which can compete one-on-one with road haulage among the countries in the Union. Despite different efforts from the public administration to kick off MoS lines and ensure their competitiveness, the expected momentum is still yet to come. In the light of this, this thesis aims at providing tools to assess the competitiveness of existing and MoS line to-be, to quantify the room for improvement available and the effects that some changes at an operational and strategical level might have on the success of any specific line. Particularly, the thesis presented aims at three specific objectives: (1) to identify the strategic potential of SSS in all its forms, considering the characteristics of the demand (goods to be moved) and the role of RoRo and MoS shipping in the global picture; (2) to identify the most sensible procedures in RoRo terminals operation to be addressed to improve their performance and perception from the end user, and; (3) To understand the costs of the supply chain, and the cost structure of RoRo shipping lines, and their sensitiveness in front of market changes, pricing and public funding policies. To approach each issue different qualitative, analytical and simulating models are used depending on the concerned problem. The strategic assessment makes use interviews to identify the main requirements that a transporter might face when dealing with SSS. The role of the terminal is assessed by means of two separate models: from one side an analytical model is used to assess the relationship between capacity and quality by means of quantifying the service time the ship spends in a port and calculate the probability of delays. On the other side, the resilience of the port is assessed with an arborescence interlinking its current vulnerabilities, their causes and effects and their probability to happen. Finally, and regarding the business models, first a cost and time model is constructed for each of them and tested against variations on some of the variables and from there, a tool to calculate the optimal deployment of the shipping line to ensure the maximum shift (or profit) is provided. In that case, the model is complemented with the adaptation of a transportation discrete choice model. Overall, the tools should be helpful to assess the potential of a shipping line from its planning level to its final operational deployment.Els darrers anys, la política de transports a nivell europeu s'ha focalitzat en reduir el pes del transport per carretera de mercaderies i promoure mitjans de transport que li siguin alternatius, com a mesures per reduir la congestió a les carreteres i la petjada ecològica. Una de les solucions que s'ha posat sobre la taula, és l'anomenat Transport Marítim de Curta Distància (TMCD o SSS, en les seves sigles en anglès), com a una veritable alternativa bimodal (ferrocarril/carretera combinats amb transport marítim) a l'opció de transport monomodal per carretera. Diversos estudis certifiquen que el transport porta-a-porta transcorregut parcialment amb TMCD acostuma a registrar menors externalitats (bàsicament costos ambientals i de congestió) que el transport per carretera per cada tona transportada. Des d'un punt de vista operatiu, el TMCD i especialment la seva versió en forma d'Autopistes del Mar (AdM o MoS), enteses com a enllaços entre ports amb altes prestacions pel que fa a temps de viatge, flexibilitat i freqüència a un cost competitiu s'han estudiat àmpliament com a una alternativa directa i equivalent al transport per carretera. Però malgrat els esforços fets des de l'administració pública per promoure les línies d'AdM i assegurar-ne la competitivitat, aquestes no han obtingut l'impuls previst inicialment. L'objectiu d'aquesta tesi, de fet, és proveir un conjunt d'eines per tal d'avaluar la competitivitat de qualsevol AdM i quantificar-ne el marge de millora i l'efecte que alguns canvis a nivell operatiu i estratègic podrien tenir en la seva competitivitat , tan a nivell operatiu com estratègic, per tal de garantir-ne la competitivitat futura. De forma més específica, la tesi que aquí es presenta, analitza tres aspectes específics de les AdM: (1) Quines característiques a de tenir el seu mercat potencial a nivell estratègic, (2) con rol prenen les terminals portuàries, enteses com la baula dèbil de la cadena de transport, a nivell de la valoració qualitativa de la cadena de transport per part del seu usuari final i (3), possibles models de negoci pel transportista / propietari de la mercaderia per treure el màxim profit de les AdM. Cada un dels tres aspectes s'adreça mitjançant eines diferenciades que s'adaptin a la problemàtica plantejada. L'anàlisi estratègic es basa en entrevistes a usuaris de cadenes de transport per establir els principals requeriments del transportista que es pugui plantejar l'ús d'una AdM. A partir dels requeriments, es defineixen diversos models de cadena de transport, arribant a la conclusió que les cadenes 'push-pull' i 'push against stock' són les candidates que més es beneficiarien d'una AdM, almenys a nivell estratègic. El rol de la terminal s'analitza qualitativament analitzant-ne dos aspectes per separat: d'una banda es crea un model basat en una combinació de valors d'origen estocàstic, determinista i via simulació, per calcular el temps d'operació mínim d'un buc de càrrega rodada a una terminal marítima i la relació que hi ha entre nivell d'ús de la terminal i la seva capacitat. D'altra banda, també s'estableix un marc per quantificar la vulnerabilitat i resiliència de la terminal davant de elements que afectin la seva normal operació i com aquests poden afectar la qualitat percebuda del servei. Finalment, pel que fa als models de negoci pels transportistes, es construeix un model de costos i temps per cada un d'ells, se n'analitza la sensibilitat i el pes de les principals variables que els afecten com a eina per calcular el model de negoci, les característiques de la línia marítima i les tarifes de base a cobrar des de la perspectiva de la naviliera. Per assolir-ho, el model es complementa amb l'adopció d'un model d'elecció modal. Preses conjuntament, es proporciona una metodologia per ajudar a avaluar el potencial de futures AdM o millorar les existents i l'efecte que hi poden tenir les actuals i futures polítiques de transport