WSC 2001 Final Abstracts

Simulation of Bored Pile Construction
Tarek M. Zayed (Zagazig University) and Daniel W. Halpin (Purdue University)

Abstract:
The installation of pile foundations is complicated by an enormous number of problems. They include unseen sub-surface obstacles, lack of contractor experience, and site planning. These major problems and other minor ones make it difficult for the estimator to evaluate the piling project productivity and cost. Therefore, this study is designed to assess these problems using simulation. Both piling process productivity and cycle time assessment are addressed. Data were collected for this study through designed questionnaires, site interviews, and telephone calls to experts in different construction companies. Many variables have been considered in the piling construction process. Two simulation models have been designed and validated to assess piling process productivity and cycle time. Consequently, two sets of charts have been developed based upon the validated models to provide the decision-maker with a solid planning, scheduling and control tool for piling projects.

Comparison of Simulation Modeling Techniques that Use Preemption to Capture Design Uncertainty
Nuno Gil and Iris D. Tommelein (University of California)

Abstract:
This paper describes a process, implemented using two simulation engines that adopt, respectively, the event scheduling paradigm and the activity scanning paradigm. The process being modeled is design development in an unpredictable environment. Unpredictability means that criteria are prone to change during design, thereby interrupting on-going work and causing design iteration. Probability density curves, input to the simulation, capture uncertainties regarding design criteria during the development of R&D semiconductor fabrication facilities. The simulation of process changes calls for preempting tasks or events, and scheduling new tasks or events. The implementations in alternative modeling paradigms illustrates the use of a top-down vs. a bottom-up approach in process modeling. The two engines that were used, SIGMA and STROBOSCOPE, both are programmable so that the model could be implemented without difficulty in either one.

Design, Development and Application of Soil Transition Algorithms for Tunneling Using Special Purpose Simulation
Janaka Y. Ruwanpura (University of Calgary) and Simaan M. AbouRizk (University of Alberta)

Abstract:
In tunnel construction, vertical boreholes only show the soil types that are present in the borehole locations. The soil profiles between the boreholes are uncertain and assumed by practitioners for construction purposes. The productivity of the tunnel construction work is therefore affected by adverse soil conditions. The successful implementation of a special purpose simulation tunneling template for project planning and decision-making identified that the modeling of uncertainties such as predicting soil conditions could provide better results. This paper presents new modeling algorithms to predict the transition of soils between the boreholes along the tunnel path. The use of transitional probabilities enables the prediction of transition points in this approach. The various scenarios of the mixed phases of soils are considered for modeling within the special purpose tunnel simulation template. Application of the simulation for modeling algorithms to a past tunnel construction proved that these modeling algorithms provide a logical and accurate prediction of the tunnel advance rate and tunnel productivity.

Simulation of Production Homebuilding Using Simphony
Anil Sawhney, Howard Bashford, Kenneth Walsh, and André Mund (Arizona State University)

Abstract:
Production homebuilders operate in a sales-driven environment characterized by a varying demand for homes that is at odds with the homebuilders’ and their trade contractors’ requirement for work flow consistency. This paper presents a simulation-based approach for studying the production flow issues that production homebuilders face. Seven scenarios, representing different practices and possibilities that the homebuilders have, are simulated using Simphony, a simulation platform intended for building Special Purpose Simulation (SPS) tools. The results of this study indicate that simulation can indeed be used to shed light on the work flow issues that production homebuilders face.

Enabling Smooth and Scalable Dynamic 3D Visualization of Discrete-Event Construction Simulations
Vineet R. Kamat and Julio C. Martinez (Virginia Polytechnic Institute and State University)

Abstract:
Visualizing simulated construction operations is an effective means of communicating the logic and the inner working of simulation models in a comprehensive and comprehendible manner. This can facilitate both model verification and validation and help establish credibility of simulation analyses. Due to the inherent working nature of discrete-event simulation systems, visualizing simulated operations in a smooth and continuous manner in 3D virtual worlds presents numerous interesting challenges. This paper describes research being conducted at Virginia Tech to enable smooth and scalable dynamic 3D visualization of discrete-event construction simulations.

Practical Approaches for Validating a Construction Simulation
Jonathan Jingsheng Shi (Illinois Institute of Technology)

Abstract:
This paper presents three methods implemented in the activity-based construction modeling and simulation (ABC) system for validating a construction simulation. The first method reports a simulation experiment in the chronological order so that the user can examine the operating sequence of the model. The second method provides the summary information of total operating counts and mean durations of all activities in the model so that the user can evaluate whether all activities have been correctly executed during simulation. The third method produces the cyclic report of a selected resource entity so that the user can examine whether the entity is moving in the correct logical and chronological order during simulation. The three methods can effectively assist the user in debugging a simulation model so as to assure that the simulation is correctly conducted. A road paving process is employed to illustrate these methods.

Using Belief Networks to Assess Risk
Brenda McCabe (Department of Civil Engineering, University of Toronto) and Donald Ford (AMEC Earth and Environmental)

Abstract:
This paper reviews two commonly used risk assessment tools, namely weighted scores and expected value. The limitations of weighted scores have been outlined. One of the more difficult aspects of the expected value method is to determine the probability of an event. A probabilistic modeling environment, called belief networks, has been proposed as an effective means of modeling the situation. An example application has been provided to show how the integrated system may work.

On the Use of Fuzzy Clustering in Construction Simulation
Mohamed Marzouk and Osama Moselhi (Concordia University)

Abstract:
This paper presents a methodology that integrates fuzzy clustering and computer simulation and demonstrates its use in modeling earthmoving operations. A simulation system (SimEarth) was developed to model earthmoving operations utilizing object-oriented features and discrete event simulation. Fuzzy clustering is used to provide realistic estimates of haulers’ travel time so as to improve the accuracy of the simulation results. A case study involving the construction of a dam is presented to illustrate the capabilities the proposed simulation engine and the developed fuzzy clustering methodology for estimating haulers’ travel time.

EZStrobe – General-Purpose Simulation System Based on Activity Cycle Diagrams
Julio C. Martinez (Virginia Tech)

Abstract:
EZStrobe is a very simple but powerful general-purpose simulation system designed for modeling construction operations, but domain independent and thus useful for modeling a wide variety of systems in any discipline. EZStrobe is based on Activity Cycle Diagrams and employs the Three-Phase Activity Scanning paradigm. It is therefore naturally adept for complex systems where many resources collaborate to carry out tasks as is typical in construction. The paper describes the basic system concepts. The paper also develops an earthmoving example in increasing levels of complexity and detail to illustrate the range of modeling capabilities.