A pareto multi-objective optimization approach for solving time-cost-quality tradeoff problems

Speeding up a project's duration will definitely increase the cost and decrease the quality. The previous literatures were mainly related to project planning and controlling which mainly focus on cost-time tradeoff. However, limited researches have been referred to project quality based on mathematical methodologies. This paper proposes a tradeoff problem on time-cost-quality performance. A computer-based Pareto multi-objective optimization approach is utilized for solving the tradeoff problems. The approach can help searching near the reality Pareto-optimal set while not receiving any information on the stakeholders’ preference for time, cost and quality. Based on the developed approach, decision-making can become easy according to the sorted non-dominated solutions and project preferences

Time-cost-quality trade-off analysis for construction projects

The main objective of construction projects is to finish the project according to an available budget, within a planned schedule, and achieving a pre-specified extent of quality. Therefore, time, cost, and quality are considered the most important attributes of construction projects. The purpose of this study is to incorporate quality into the traditional two-dimensional time-cost trade-off (TCT) in order to develop an advanced three-dimensional time-cost-quality trade-off (TCQT) approach. Time, cost, and quality of construction projects are interrelated and have impacts on each other. It is a challenging task to strike a balance among these three conflicting objectives of construction projects since no one solution can be optimal for the three objectives. The overall performance of a project regarding time, cost, and quality is determined by the duration, cost, and quality of its activities. These attributes of each activity depend on the execution option by which the activity’s work is completed. It is required to develop an approach that is capable of finding an optimal or near optimal set of execution options for the project’s activities in order to minimize the project’s total cost and total duration, while its overall quality is maximized. For the aforementioned purpose, three various Microsoft Excel based TCQT models have been developed as follows: • First, a simplified model is developed with the objective of optimizing the total duration, cost, and quality of simple construction projects utilizing the GA-based Excel add in Evolver. • Second, a stochastic model is developed with the objective of optimizing the total duration, cost, and quality of construction projects applying the PERT approach in order to consider uncertainty associated with the performance of execution options and the whole project. • Third, an advanced multi objective optimization model is developed utilizing a self-developed optimization tool having the following capabilities: 1. Selecting an appropriate execution option for each activity within a considered project to optimize the objectives of time, cost, and quality. 2. Considering the discrete nature of duration, cost, and quality of various options for executing each activity. 3. Applying three various optimization approaches, which are the Goal Programming (GP), the Modified Adaptive Weight Approach (MAWA), and the Non-dominated Sorting Genetic Algorithms (NSGAII). 4. Analyzing both TCT and TCQT problems. 5. Considering finish-to-finish, start-to-start, and start-to-finish dependency relationships in addition to the traditional finish-to-start relationships among activities. 6. Considering any number of successors and predecessors for activities. 7. User-friendly input and output interfaces to be used for large-scale projects. To validate the developed models and demonstrate their efficiency, they were applied to case studies introduced in literature. Results obtained by the developed models demonstrated their effectiveness and efficiency in analyzing both TCT and TCQT problems

Project Schedule Compression Considering Multi-objective Decision Environment

This research aims to present a new method to circumvent the limitations of current schedule compression methods, which reduce schedule crashing to the traditional time-cost trade-off analysis, where only cost is considered. In this research the schedule compression process is modeled as a multi-attributed decision making problem in which different factors contribute to priority setting for activity crashing. For this purpose, a modified format of the Multiple Binary Decision Method (MBDM) and an iterative crashing process are utilized. The developed method is implemented in Visual Basic 2010 environment, with a dynamic link to MS-Project to facilitate the needed iterative rescheduling of project activities. To demonstrate the use of the developed method and to highlight its capabilities, 3 case examples drawn from literature were analyzed. When considering cost only, the generated results were in good agreement with those generated using the Harmony Search method, Genetic Algorithms and iterative crashing process used in original examples, particularly in capturing the project least-cost duration. However, when other factors in addition to cost were considered, as expected, different project least-cost and associated durations were obtained. The novelty of the developed method lies in its capacity to allow for the consideration of a number of factors in addition to cost. Also through its allowance for possible variations in the relative importance of these factors at the individual activity level, it provides contractors with a number of compression execution plans and assists them in identifying the most suitable plan. Accordingly, it enables the integration of contractors’ judgment and experience in the crashing process and permits consideration of different project environments and constraints

Improving decision making for incentivised and weather-sensitive projects

The field of project management has originated from the domain of operational research, which focuses on the mathematical optimization of operational problems. However, in recent decades an increasingly broad perspective has been applied to the field of project management. As such, project management has spawned a number of very active sub- domains, which focus not solely on the scheduling of the project’s baseline, but also on the analysis of risk, as well as the controlling of project execution. This dissertation focuses on two areas where existing literature is still lacking. The first area is the use of incentivised contractual agreements between the owner of a project, and the contractor who is hired to execute the project. Whereas this area has received growing attention in recent years, the majority of studies remained strongly descriptive. Hence, the aim of the first part of this dissertation is to develop a more prescriptive approach from both the owner’s and the contractor’s perspective. The second part of this dissertation investigates the use of dedicated weather models to improve operational performance of weather-sensitive projects. During recent decades, significant effort has been made to improve the quality of weather simulation models. Moreover, the amount of available weather data has been steadily increasing. This opens up a lot of new possibilities for using more precise weather models in order to support operational decision making. In spite of this, the number of applications of these weather models in operational research has remained rather limited. As such, the aim of the second part of this dissertation is to leverage these weather models to improve the scheduling of offshore construction projects, as well as preventive maintenance of offshore wind turbines

Development of the concept of strategic benefit management in portfolio of projects

Istraživanje prikazano u okviru doktorske disertacije se bavi razvojem i testiranjem koncepta strateškog upravljanja koristima kao sistema modela, koji treba da doprinesu optimalnom upravljanju koristima kroz sve faze životnog ciklusa projektnog i portfolio menadžmenta. U ovoj disertaciji je najpre dat teorijski prikaz koncepta, polazeći od šire naučne osnove, preko njegovog teorijskog objašnjenja, pa do detaljne analize modela, sastavnih elemenata koncepta. U radu su definisana tri modela koji su sastavni delovi koncepta i svaki od njih se tiče po jedne faze u stvaranju projektnih koristi. Koncept strateškog upravljanja koristima ima interdisciplinarni karakter, obzirom na to da obuhvata različite oblasti projektnog menadžmenta, operacionih istraživanja i analize zrelosti sistema menadžmenta. U istraživačkom delu rada, koncept strateškog upravljanja koristima je testiran u oblasti portfolia projekata energetske efikasnosti u javnim zgradama. Specifičnost ovih projekata je da donose različite tipove koristi, pa su samim tim i pogodni za testiranje koncepta. Koristeći podatke o realizovanim projektima, istraživanje je nastojalo da utvrdi da li bi primena koncepta strateškog upravljanja koristima dala bolje rezultate u odnosu na poznate metode koje se primenjuju u praksi. Shodno rezultatima istraživanja, date su i preporuke o poboljšanju prakse projektnog i portfolio menadžmenta u oblasti poboljšanja energetske efikasnosti, ali i uopšte, kao i o daljim istraživanjima koja se tiču upravljanja projektnim koristima.The research presented in the doctoral dissertation deals with the development and testing of the concept of strategic benefit management as a system of models, which should contribute to the optimal benefit management through all phases of the development life cycle of project and portfolio management. In this dissertation, firstly, the theoretical presentation of the concept is given, starting from a wider scientific basis, through its theoretical explanation, to a detailed analysis of the models, the constituent elements of the concept. The paper defines three models that are integral parts of the concept and each of them relates to one phase in the creation of project benefits. The concept of strategic benefit management has an interdisciplinary character, as it covers various areas of project management, operational research and analysis of management systems maturity. In the research part of the paper, the concept of strategic benefit management has been tested in the portfolio of energy efficiency projects in public buildings. The specificity of these projects is that they bring different types of benefits, so they are also suitable for testing the concept. Using data on realized projects, the research sought to determine whether the application of the concept of strategic benefit management would yield better results than the known methods applied in practice. According to the results of the research, recommendations were given on improving the project and portfolio management practices in the field of energy efficiency improvement, but also in general, as well as on further research concerning the project benefit management

The Role of Lean and Agile Logistics during Production Ramp-Up

In addition to the rareness of theoretical and empirical research, which extends to every aspect of the production ramp-up literature, the increasing importance of the ramp-up phase – due to the continuously decreasing product lifecycle in almost all industrial sectors –magnifies the need for more research efforts in this field. Based on a comprehensive literature review, no attempts to investigate the role of lean and/or agile logistics during the ramp-up stage were found. Utilizing the survey method, this research empirically explores the effects of lean and agile logistics on production performance during the ramp-up phase in terms of quantity, quality, and cost. A special purpose questionnaire was developed to collect primary data based on a literature review in the fields of production ramp-up, lean logistics, lean production, agile logistics, agile production, performance measurement, and product success. The measurement model was evaluated for validity and reliability and tested for temporal consistency and the existence of common method variance; the collected data were tested for measurement and non-response biases; and the results were evaluated for their statistical power and statistical conclusion error. Out of 63 questionnaires collected from industrial organizations operating in 7 countries and in different sectors, 56 responses were used in the statistical analyses. A two-step methodological approach was utilized in the data analysis. In the first step, the data collected on the research variables were analysed following a theory confirmation procedure to examine the validity of a hypothesized positive effect of lean and agile logistics on ramp-up performance. In addition, the effect of ramp-up performance on new products’ success, the moderating effect of some respondent, organizational, and product-related variables, and the mediating effect of outbound logistics were investigated. The partial least squares method of structural equation modelling (PLS-SEM) was employed during the confirmatory analysis. Different scenarios were evaluated to test the main and subsidiary hypotheses proposed, based on the use of formative and reflective measures and first- or higher-order variable formats. The results of the confirmatory data analysis supported the hypothesized positive effect of lean and agile logistics on production performance during the ramp-up phase. In the second methodological step, exploratory analyses were conducted to explore further patterns in the data collected. Correlation matrices indicated a greater effect of agility on quantity performance and a greater effect of leanness on cost performance. Such trends are generally accepted and supported by the theoretical literature and by practitioners. However, the agreed-upon priorities of time reduction during the ramp-up phase and cost reduction during the steady-state and ramp-down phases motivated the proposition of a mixed model that uses higher levels of agility throughout the ramp-up phase and higher leanness levels thereafter. The proposed mixed system was supposed to outperform the pure lean, pure agile, and leagile strategies. Among the methods proposed to apply such a mixed production system, the development of a specialized agile ramp-up facility was introduced. It was suggested that all products undergoing a ramp-up phase should be produced with an agile system, in a specialized ramp-up facility, and then moved to a lean facility during the steady-state and ramp-down production phases. To examine the feasibility of the proposed system and the magnitude of investment that might be accepted to gain the expected enhancement, the total lifecycle profitability of each system – lean, agile, leagile, and mixed – was calculated and compared to provide insights into the advantages of the mixed system and the conditions that increase or decrease the appeal of investing in such a strategy. It was concluded that the adoption of the proposed system and the asset investment magnitude should be evaluated considering different possible combinations of the product’s type, price, cost, contribution, and lifecycle length, among other variables. The proposed system has been proven to be more attractive to adopt as the proportion of the ramp-up time to the total lifecycle increases, as the product’s price drops faster, as the peak sales are reached earlier, or as the number of ramp-ups increases

Prise en compte de la flexibilité des ressources humaines dans la planification et l’ordonnancement des activités industrielles

Le besoin croissant de réactivité dans les différents secteurs industriels face à la volatilité des marchés soulève une forte demande de la flexibilité dans leur organisation. Cette flexibilité peut être utilisée pour améliorer la robustesse du planning de référence d’un programme d’activités donné. Les ressources humaines de l’entreprise étant de plus en plus considérées comme le coeur des structures organisationnelles, elles représentent une source de flexibilité renouvelable et viable. Tout d’abord, ce travail a été mis en oeuvre pour modéliser le problème d’affectation multi-périodes des effectifs sur les activités industrielles en considérant deux dimensions de la flexibilité: L’annualisation du temps de travail, qui concerne les politiques de modulation d’horaires, individuels ou collectifs, et la polyvalence des opérateurs, qui induit une vision dynamique de leurs compétences et la nécessité de prévoir les évolutions des performances individuelles en fonction des affectations successives. La nature dynamique de l’efficacité des effectifs a été modélisée en fonction de l’apprentissage par la pratique et de la perte de compétence pendant les périodes d’interruption du travail. En conséquence, nous sommes résolument placés dans un contexte où la durée prévue des activités n’est plus déterministe, mais résulte du nombre des acteurs choisis pour les exécuter, en plus des niveaux de leur expérience. Ensuite, la recherche a été orientée pour répondre à la question : « quelle genre, ou quelle taille, de problème pose le projet que nous devons planifier? ». Par conséquent, les différentes dimensions du problème posé sont classées et analysés pour être évaluées et mesurées. Pour chaque dimension, la méthode d’évaluation la plus pertinente a été proposée : le travail a ensuite consisté à réduire les paramètres résultants en composantes principales en procédant à une analyse factorielle. En résultat, la complexité (ou la simplicité) de la recherche de solution (c’est-à-dire de l’élaboration d’un planning satisfaisant pour un problème donné) peut être évaluée. Pour ce faire, nous avons développé une plate-forme logicielle destinée à résoudre le problème et construire le planning de référence du projet avec l’affectation des ressources associées, plate-forme basée sur les algorithmes génétiques. Le modèle a été validé, et ses paramètres ont été affinés via des plans d’expériences pour garantir la meilleure performance. De plus, la robustesse de ces performances a été étudiée sur la résolution complète d’un échantillon de quatre cents projets, classés selon le nombre de leurs tâches. En raison de l’aspect dynamique de l’efficacité des opérateurs, le présent travail examine un ensemble de facteurs qui influencent le développement de leur polyvalence. Les résultats concluent logiquement qu’une entreprise en quête de flexibilité doit accepter des coûts supplémentaires pour développer la polyvalence de ses opérateurs. Afin de maîtriser ces surcoûts, le nombre des opérateurs qui suivent un programme de développement des compétences doit être optimisé, ainsi que, pour chacun d’eux, le degré de ressemblance entre les nouvelles compétences développées et les compétences initiales, ou le nombre de ces compétences complémentaires (toujours pour chacun d’eux), ainsi enfin que la façon dont les heures de travail des opérateurs doivent être réparties sur la période d’acquisition des compétences. Enfin, ce travail ouvre la porte pour la prise en compte future des facteurs humains et de la flexibilité des effectifs pendant l’élaboration d’un planning de référence. ABSTRACT : The growing need of responsiveness for manufacturing companies facing the market volatility raises a strong demand for flexibility in their organization. This flexibility can be used to enhance the robustness of a baseline schedule for a given programme of activities. Since the company personnel are increasingly seen as the core of the organizational structures, they provide the decision-makers with a source of renewable and viable flexibility. First, this work was implemented to model the problem of multi-period workforce allocation on industrial activities with two degrees of flexibility: the annualizing of the working time, which offers opportunities of changing the schedules, individually as well as collectively. The second degree of flexibility is the versatility of operators, which induces a dynamic view of their skills and the need to predict changes in individual performances as a result of successive assignments. The dynamic nature of workforce’s experience was modelled in function of learning-by-doing and of oblivion phenomenon during the work interruption periods. We firmly set ourselves in a context where the expected durations of activities are no longer deterministic, but result from the number and levels of experience of the workers assigned to perform them. After that, the research was oriented to answer the question “What kind of problem is raises the project we are facing to schedule?”: therefore the different dimensions of the project are inventoried and analysed to be measured. For each of these dimensions, the related sensitive assessment methods have been proposed. Relying on the produced correlated measures, the research proposes to aggregate them through a factor analysis in order to produce the main principal components of an instance. Consequently, the complexity or the easiness of solving or realising a given scheduling problem can be evaluated. In that view, we developed a platform software to solve the problem and construct the project baseline schedule with the associated resources allocation. This platform relies on a genetic algorithm. The model has been validated, moreover, its parameters has been tuned to give the best performance, relying on an experimental design procedure. The robustness of its performance was also investigated, by a comprehensive solving of four hundred instances of projects, ranked according to the number of their tasks. Due to the dynamic aspect of the workforce’s experience, this research work investigates a set of different parameters affecting the development of their versatility. The results recommend that the firms seeking for flexibility should accept an amount of extra cost to develop the operators’ multi functionality. In order to control these over-costs, the number of operators who attend a skill development program should be optimised, as well as the similarity of the new developed skills relative to the principal ones, or the number of the additional skills an operator may be trained to, or finally the way the operators’ working hours should be distributed along the period of skill acquisition: this is the field of investigations of the present work which will, in the end, open the door for considering human factors and workforce’s flexibility in generating a work baseline program

Considering the flexibility of human resources in planning and scheduling industrial activities

The growing need of responsiveness for manufacturing companies facing the market volatility raises a strong demand for flexibility in their organization. This flexibility can be used to enhance the robustness of a baseline schedule for a given programme of activities. Since the company personnel are increasingly seen as the core of the organizational structures, they provide the decision-makers with a source of renewable and viable flexibility. First, this work was implemented to model the problem of multi-period workforce allocation on industrial activities with two degrees of flexibility: the annualizing of the working time, which offers opportunities of changing the schedules, individually as well as collectively. The second degree of flexibility is the versatility of operators, which induces a dynamic view of their skills and the need to predict changes in individual performances as a result of successive assignments. The dynamic nature of workforce’s experience was modelled in function of learning-by-doing and of oblivion phenomenon during the work interruption periods. We firmly set ourselves in a context where the expected durations of activities are no longer deterministic, but result from the number and levels of experience of the workers assigned to perform them. After that, the research was oriented to answer the question “What kind of problem is raises the project we are facing to schedule?”: therefore the different dimensions of the project are inventoried and analysed to be measured. For each of these dimensions, the related sensitive assessment methods have been proposed. Relying on the produced correlated measures, the research proposes to aggregate them through a factor analysis in order to produce the main principal components of an instance. Consequently, the complexity or the easiness of solving or realising a given scheduling problem can be evaluated. In that view, we developed a platform software to solve the problem and construct the project baseline schedule with the associated resources allocation. This platform relies on a genetic algorithm. The model has been validated, moreover, its parameters has been tuned to give the best performance, relying on an experimental design procedure. The robustness of its performance was also investigated, by a comprehensive solving of four hundred instances of projects, ranked according to the number of their tasks. Due to the dynamic aspect of the workforce’s experience, this research work investigates a set of different parameters affecting the development of their versatility. The results recommend that the firms seeking for flexibility should accept an amount of extra cost to develop the operators’ multi functionality. In order to control these over-costs, the number of operators who attend a skill development program should be optimised, as well as the similarity of the new developed skills relative to the principal ones, or the number of the additional skills an operator may be trained to, or finally the way the operators’ working hours should be distributed along the period of skill acquisition: this is the field of investigations of the present work which will, in the end, open the door for considering human factors and workforce’s flexibility in generating a work baseline program