Constrained Project Scheduling Problem Research Articles

A CNPVaR-NPV Trade-off Model for Resource- Constrained Project Scheduling Problem Under Random Environment

Projects face various risks and opportunities throughout their lifecycle. Integrating risk management into the project progression is a crucial factor for project success and an essential component of project management. This paper aims to evaluate the trade-off between Conditional Net Present Value at Risk (CNPVaR) and Net Present Value (NPV) in a stochastic environment. By assuming the activity duration and cash flow as random variables and setting activity start and execution modes as decision variables, a CNPVaR-NPV trade-off model is established with the objectives of minimizing CNPVaR and maximizing NPV, under priority relationships, execution mode, resource supply, and deadlines constraints. Based on the characteristics of the model, an algorithm combining nondominated sorting genetic algorithm II and Monte Carlo simulation is designed. The HVAC system project of Dongguan Jinyun Digital Park 5# Building is used as a case study to illustrate the effectiveness of the model and the algorithm. The results show that considering the CNPVaRNPV trade-off model can effectively mitigate potential risks and reduce project losses.

Resource Unconstrained and Constrained Project Scheduling Problems and Practices in a Multiproject Environment

Construction companies execute many projects simultaneously. In such situations, the performance of one project may influence the others positively or negatively. Construction professionals face difficulties in managing multiple projects in limited resource situations. The purpose of this study is to identify the problems in multiproject scheduling from the practitioner’s perspective and to discover current practices under resource unconstrained and constrained settings. The specific objectives are (1) determining the most challenging issues being faced in handling multiproject environment, (2) enumerating the practices adopted in the industry, and finally (3) identifying the practitioners' perceptions on the multiproject scheduling aspects such as network modeling approaches; activity execution modes; concept of sharing, dedicating, and substituting resources; centralized and decentralized decision-making models; solution approaches; and tools and techniques. An online questionnaire survey was conducted to address the objectives above. The top challenging issues in managing multiproject environment are identified. Factor analysis identified the factors by grouping the variables (a) decision-related, (b) project environment-related, (c) project management-related, and (d) organization-related factors. Resource-unconstrained situation mainly faces the issue of underutilization and wastage of resources leading to lower profit realization. The following findings were identified to overcome the unconstrained resource situation such as identifying the work front, adopting pull planning approach, creating a common resource pool, and allotting it on a rental basis. On the contrary, resource-constrained situation faces the issues of prioritization of resources, coordination, communication, collaboration, quality issues, and rework. The findings suggest the strategies such as top-up via subcontracting, proactive pull planning, introducing buffers, training the culture of the organization towards better communication, coordination, and collaboration, to improve the reliability of achieving baseline project performances. Various multiproject aspects suggested for effective management. The identified problems, practices, and various multiproject aspects are expected to contribute better management of multiproject resource unconstrained and constrained project scheduling.

A HEURISTIC IMPROVED METHOD BASED ON THE PRIORITY FOR CONSTRAINED PROJECT SCHEDULING PROBLEM WITH FUZZY PARAMETERS

Abstract. In this research at first some of the most important previous studies in the field of fuzzy project planning and its various solving procedures are reviewed and introduced. Then after introducing the problem model and considering its theories, one of the most creative approaches for solving the Constrained and definite Project Scheduling Problem has improved and deployed with allowing time parameters and fuzzy resource to solve the problem. With utilizing one of the presented approaches in previous researches the needed operations for computing the priorities were improved and finally the proposed algorithm in the total form and ability to solve the mentioned fuzzy problems in different dimensions were offered and described. After programming of the proposed algorithm with visual c#, 120 problem instances with different properties was solved by the algorithm and the priorities were ranked and analyzed with respect to its results. With respect to use a way for ranking fuzzy numbers in this algorithm, some of the different presented mentioned ways in previous researches and categories have been also reviewed. At the end some suggestions for developing the model and applying the other theories in problem model were presented for further researches.

Robust Buffer Allocation for Scheduling of a Project with Predefined Milestones

The paper discusses the problem of robust buffer allocation for Resource- Constrained Project Scheduling Problem (RCPSP) with predefined milestones, for which execution deadlines have been established. To solve the problem, an algorithm is proposed supporting insertion of unit time buffers, with the simultaneous maximisation of new metrics of arrangement robustness. The presented results of experimental research speak for usability of the solutions proposed. The effectiveness is studied with use of test tasks included in the Project Scheduling Problem Library (PSPLIB) with additionally specified project milestones.

A comparative morphologic analysis of benchmark sets of project networks

The performance of methods to manage projects depends heavily on the features of their project networks. This is particularly true for methods devoted to project scheduling, risk analysis and resources allocation. Therefore, a long line of research has been developed to generate benchmark sets of project networks and several sets have been proposed in the literature. Unfortunately, no comparative analyses of their features were published and hence serious doubts about the comparability of results using different benchmark sets can be raised. In this paper, a multi-dimensional taxonomy for the morphology of project networks is used and four benchmark sets are evaluated: Patterson collection of problems (Patterson JH. A comparison of exact approaches for solving the multiple constrained resource, project scheduling problem. Management Science 1984;30:854–867) and the sets produced by the generators due to Agrawal et al. Agrawal MK, Elmaghraby SE, Herroelen WS. DAGEN a generator of testsets for project activity nets. European Journal of Operational Research 1996;90:376–382, Kolisch et al. Kolisch R, Sprecher A, Drexl A. Characterization and generation of a general class of resource — constrained project scheduling problems. Management Science 1995;41:1693–1703, Tavares Tavares LV. Advanced models in project management. Kluwer, 1999 and Tavares et al. Tavares LV, Antunes Ferreira JA, Coelho JS. The risk of delay of a project in terms of the morphology of its network. European Journal of Operational Research 1999;119:510–537. Original results about the lack of representativeness of these sets are obtained showing that misleading conclusions can be deduced. The last set is, by far, that one covering most extensively the morphologic space of instances which could be foreseen because the generation of networks is carried out in terms of an wider range of parameters. This conclusion is quite useful for project managers willing to assess alternative methods to solve their problems based on project networks.

Resource allocation with project management software

We present results of a benchmark test evaluating the resource allocation capabilities of the project management software packages Acos Plus.1 8.2, CA SuperProject 5.0a, CS Project Professional 3.0, MS Project 2000, and Scitor Project Scheduler 8.0.1. The tests are based on 1560 instances of precedence--- and resource---constrained project scheduling problems. For different complexity scenarios, we analyze the deviation of the makespan obtained by the software packages from the best feasible makespan known. Among the tested software packages, Acos Plus.1 and Project Scheduler show the best resource allocation performance. Moreover, our numerical analysis reveals a considerable performance gap between the implemented methods and state---of---the---art project scheduling algorithms, especially for large---sized problems. Thus, there is still a significant potential for improving solutions to resource allocation problems in practice.