WSC 2005 Final Abstracts

Simulation of Multiple-drift Tunnel Construction with Limited Resources
Photios G. Ioannou (University of Michigan) and Veerasak Likhitruangsilp (Chulalongkorn University)

Abstract:
Construction work is often performed with limited resources. The optimal dynamic allocation of resources at simulation runtime sometimes requires that non-critical tasks be held back deliberately and not be allowed to start so that resources will be available to perform more critical activities later. This is an important issue that has escaped rigorous investigation. For certain projects it may be more expedient to model work at the activity level and not the resource level and embed the routing of resources into precedence relationships. The Hanging Lake Tunneling Project is presented as an example where the estimation of tunnel advance rates for all tunneling alternatives is performed at the activity level and where the allocation of limited resources is encapsulated in tunneling plans particular to the tunneling alternative being analyzed.

The Use of Simulation for Productivity Estimation Based on Multiple Regression Analysis
Seungwoo Han (Georgia Southern University) and Daniel W. Halpin (Purdue University)

Abstract:
Productivity estimation has been fundamental subject investigated in academia and industry. There are two common methods for estimation of productivity: (1) deterministic and (2) simulation methods. The deterministic method does not reflect actual conditions, such as randomness of work duration, whereas simulation method can overcome this limitation. However, the user without a background in simulation may struggle with implementation due to the difficulty of modeling. The presented productivity estimation model in this research was created using multiple regression analysis with data generated by WebCYCLONE. The model representing the mathematical relations between conditions and productivity allows planners or site personnel to estimate productivity by simply entering input data reflecting actual site conditions. In academia, the research methodology utilized in this research provides a framework for the user to establish other application models for estimating or evaluating the performances of new technologies.

Modeling Scheduling Uncertainty in Capital Construction Projects
Nathan D. Boskers (Springwood Developments Inc.) and S. M. AbouRizk (University of Alberta)

Abstract:
Capital infrastructure projects with long-term implementation time frames are generally uncertain in nature. Engineers and planners attempting to estimate the costs of such projects often resort to using contingencies based on their experience without proper modeling of the uncertainty of costs, durations, or economic conditions. This paper presents a simulation-based model for assessing uncertainty associated with these projects. In particular the model accounts for expected fluctuations in the costs and durations of various work packages and, most significantly, it accounts for the inflation of costs over time based on when the work packages occur. The model uses Monte Carlo simulation techniques to account for time and cost and uses non-stationary time series modeling techniques to predict inflation rates. The model is implemented as a special purpose simulation template available in the public domain.

System Dynamics Approach for Error and Change Management in Concurrent Design and Construction
SangHyun Lee (MIT) and Feniosky Pena-mora (UIUC)

Abstract:
Errors and changes, particularly in concurrent design and construction, require a careful approach to their management, since they can generate unanticipated impacts on construction performance, which is often related to softer aspects of management (e.g., fatigue). Focusing on this issue, this paper explores the use of system dynamics in identifying multiple feedback processes and softer aspects of managing errors and changes. Applying the developed model into the design-build highway project in Massachusetts, this paper concludes that the system dynamics approach can be an effective tool in the understanding of complex and dynamic construction processes and in supporting the decision making process of making appropriate policies to improve construction performance.

Intelligent Preemption in Construction of a Manmade Island for an Airport
Photios G. Ioannou and Vineet R. Kamat (University of Michigan)

Abstract:
This paper presents the simulation model and 3D animation for a project involving large-scale undersea land reclamation for the construction of a manmade island for an airport. The model illustrates how intelligent preemption can be dynamically used at simulation runtime to enforce the operational policies of a tug boat that guides barges loaded with earth into the island for unloading and then out into the sea after unloading is complete. The example also investigates the repeated stalling of the otherwise continuous unloading operations due to the need to share the narrow island entrance channel with watercraft supporting other construction activities. The solution to this problem is outlined conceptually using the activity-scanning modeling paradigm. The solution is described in detail using a simulation model developed in STROBOSCOPE and a 3D animation created using VITASCOPE.

Comparing Promodel and Sdesa in Modeling Construciton Operations
Ming Lu and Lap-Chi Wong (Hong Kong Polytechnic University)

Abstract:
The research presented applies the PROMODEL alongside a simplified discrete-event simulation approach (SDESA) and its software platform resulting from in-house construction research for modeling typical construction operations. The characteristics and modeling needs for construction and manufacturing systems are compared in general. A simple earth-moving operation and a real site operation integrating concreting and waste handling practices serve as case studies to illustrate the features, advantages, and limitations of PROMODEL and SDESA. It is found that SDESA can adequately, precisely depict the construction operations with much less learning and modeling efforts compared with PROMODEL. Particular comparisons between the two methodologies are made on (1) resource transit times, (2) activity priorities, (3) resource utilization rates, and (4) basic model structures (i.e. production-line vs. vehicle-loop).

Reviving a Mechanistic View of CPM Schedules in the Age of Information Technology
Gunnar Lucko (The Catholic University of America)

Abstract:
This paper argues for reviving a more mechanistic view of CPM scheduling. It first reviews the clarity of displaying both the time and logic information of schedules in the graphics outputs of scheduling software used in construction practice. While such software offers an abundance of features, the true nature of schedules may remain hidden behind graphics defaults. Two methods introduced in the literature, fenced bar charts and a mechanical model, are then brought forth as examples of techniques supporting an intuitive structural understanding of schedules. Both stress the equal importance of activities and logic links for displaying schedules. Comparisons between these mechanistic methods and scheduling software are drawn and recommendations for achieving optimum graphical representations of schedules are provided. Eventually, a revised approach that acknowledges the complexity of schedules and the need for their unambiguous display can contribute to reducing errors and to an overall improved use of CPM scheduling.

Representation and Analysis of Spatial Resources in Construction Simulation
Cheng Zhang, Amin Hammad, and Tarek M. Zayed (Concordia University) and Gabriel Wainer (Carleton University)

Abstract:
Space is one of the resources that may cause crucial problems during construction. Discrete event simulation has been widely used in construction to allocate resources and improve productivity or mitigate conflicts. However, simulation research that provides an explicit method to investigate possible space conflicts is still limited. This paper suggests a cell-based method to represent space resources in construction simulation, which enables conflict analysis and visual display of the worksite and the occupation of spaces. Different simulation models are compared to identify their limitations in space representation.

Determination of Process Durations on Virtual Construction Sites
Hans-Joachim Bargstädt and Arno Blickling (Bauhaus University Weimar)

Abstract:
The paper analyses the application of 3D gaming technologies in the simulation of processes associated with human resources and machinery on construction sites in order to determine process costs. It addresses the problem of detailing in process simulation. The authors outline special boundary conditions for the simulation of cost-relevant resource processes on virtual construction sites. The approach considers different needs for detailing in process simulation during the planning and building phase. For simulation of process costs on a construction site (contractors` view) the level of detail has to be high. A prototype for determination of process durations (and hereby process costs) developed at the Bauhaus University Weimar is presented as a result of ongoing researches on detailing in process simulation. It shows the method of process cost determination on a high level of detail (game between excavator and truck) through interaction with the virtual environment of the site.