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Title: Study of time extensions and the cost implications in construction project scheduling
Authors: Siu, Ming-fung
Degree: M.Phil.
Issue Date: 2011
Abstract: Despite meticulous planning effort, extension to project completion time is commonplace on real-world construction projects due to increased scope and complexity of work at activity levels and lower productivity resulting from a wide range of practical constraints related to environment, equipment, labor, materials, and management. The project time extension (PTE, representing project delay) is largely attributed to activity time extensions (ATE, representing activity delay) which occur on multiple activities during the execution stage of a construction project. Time extension and the associated cost overspend are generally indicative of flawed project execution or potential project delivery failure in project management. Effective time control is vital to project planning, monitoring and control. Approaches that are currently and commonly used for scheduling analysis in qualifying project and activity time extensions, such as critical path method (CPM) and earned value management (EVM), are analytically convoluted. In the traditional CPM framework, activity total float (TF) represents the amount of time by which an activity can be delayed without extending the scheduled project time. This classic definition fails to cope with project time extension effects resulting from complicated relationships between project and activity delays. On the other hand, earned value management (EVM) assumes an ideal baseline schedule and thus is inadequate to tackle resource-constrained scheduling under delayed scenarios. The focus of this research study has been therefore narrowed down to refining the TF definition in the CPM framework and improving the EVM framework, by characterizing the relationships between activity time extension (ATE) and project time extension (PTE). In this study, scheduling simulations are employed for accurate schedule analysis as the CPM schedule, in practice, entails imposing resource constraints on construction projects. Such constraints include resource daily available limits and non-working time defined by resource calendars. Commonly used scheduling simulation tools, Primavera® P3™ Project Planner (P3), is used to generate resource-constrained schedules in this research study.
The relationships between ATE and PTE are contrasted using evidence obtained from a simple project which is taken from Kraiem and Diekmann (1987). The results prove that the PTE-ATE relationship function exhibits high non-linearity when activity calendar constraints are imposed. Based on the in-depth understanding of ATE and PTE relationships, simulation-based activity TF determination methodologies are developed in this research to enable effective project time extension planning and control. TF, which is a non-negative activity attribute, provides a time control measure to control the ATE and achieve the objective of avoiding or minimizing PTE. The algorithm is proposed to determine TF given a particular PTE level. Further, the algorithm is proposed to cope with a set of delayed activities, each of which experiences a certain level of ATE. The proposed TF determination methodologies provide the flexibility to characterize the relationships between project delay and multiple activity delays for a specific scenario. The simulation-based TF determination methodologies were successfully implemented on a highway widening construction project. The potential applications of project completion time control and activity delay analysis were demonstrated. The results prove that for a particular set of delayed activities, the ATE can be controlled based on TF evaluated by proposed methodologies, given a particular PTE level. Project cost increase is generally a by-product of project time extension. The schedule and cost management integrated approach of EVM is currently widely utilized in tracking the project schedule and cost performances. It is found that EVM can only be applied to ideal scheduling scenarios without practical constraints and complicated activity-project delays. The EVM fails to account for dynamic changes of project status in terms of project time extension and cost overrun, potentially generating misleading project performance tracking indicators. Hence, EVM is refined based on an in-depth understanding of ATE and PTE gained in the TF determination study. This improved simulation-based approach was successfully applied in a simple project taken from Ahuja et al. (1994). The results indicated that this established EVM approach is conducive to truthfully reflecting the project performance status given a resource-constrained schedule subject to complicated activity-project delay scenarios. However, limitations are identified in terms of quantitatively assessing the project performance by tracking scope change, work done and actual expenses on a continuous basis; and seamlessly connecting EVM indicators with TF determined from schedule simulations. Those limitations present further research opportunities in the future. Simulation-based activity total float determination methodologies and an enhancement of earned value management for time extension planning, tracking and control have been developed in this research. The newly developed methodologies, the complete project data set plus observations and findings generalized from case studies will add to the body of knowledge in project management. The deliverables and findings from this study will benefit construction practitioners in planning and control of challenging resource-constrained construction projects, providing a broader view of activity and project time extension analysis and the associated cost implications in construction project scheduling.
Subjects: Construction industry -- Management.
Building -- Superintendence.
Production scheduling.
Project management.
Hong Kong Polytechnic University -- Dissertations
Pages: xviii, 136 leaves : ill. (some col.) ; 30 cm.
Appears in Collections:Thesis

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