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Four-Dimensional Visualization of Construction Schedulingand Site Utilization

K. W. Chau1; M. Anson2; and J. P. Zhang3

Abstract: Four-dimensional~4D! models link three-dimensional geometrical models with construction schedule data. The visbetween the schedule and construction site conditions is capable of facilitating decision making during both the planning and cstages. The emphases of these 4D developments have often been placed at the level of construction components. Pracassisting site management are at times lacking in the following areas:~1! generation of site usage layouts;~2! estimation of quantities oconstruction materials; and~3! cost evaluation. In order to pinpoint these deficiencies, the objective of this work is to enable visuof the effects of job progress on the logistics and resource schedules. This paper presents a 4D visualization model that is into help construction managers plan day-to-day activities more efficiently in a broader and more practical site management conthereby add to our knowledge and understanding of the relevance of modern computer graphics to the responsibilities of the csite manager. A brief site trial of the software is described at the conclusion of the paper.

DOI: 10.1061/~ASCE!0733-9364~2004!130:4~598!

CE Database subject headings: Computer aided scheduling; Graphic methods; Construction management; Construction pThree-dimensional models; Construction sites.

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Introduction

Comprehensive planning and the efficient layout of site facilare important factors contributing to successful constructionagement. A major characteristic of a contemporary construproject is its complex and multidisciplinary nature. This in tdemands more site staff effort and higher standards in planand communication. It should be noted, however, that for mconstruction projects, the client’s requirements are still resented in terms of paper-based working drawings. An impotask for the contractor is to formulate a project schedule thatdifferent construction activities on the basis of these wordrawings. In this process, planners have to take into considepractical construction sequence, proper workspace logisticsfeasible resource allocation, which includes labor, mateequipment, and the use of site space.

In practice, the initial site layout drawings that show theorganization and utilization are normally not updated as constion progresses. Planners usually only internally conceptunew facilities arrangements as the conditions evolve. This laa formal representation cannot truly reflect the fact that thelayout is intuitively dependent on the construction sched

1Dept. of Civil and Structural Engineering, Hong Kong PolytechUniv., Hunghom, Kowloon, Hong Kong.

2Dept. of Civil and Structural Engineering, Hong Kong PolytechUniv., Hunghom, Kowloon, Hong Kong.

3Dept. of Civil Engineering, Tsinghua Univ., Beijing, PeoplRepublic of China.

Note. Discussion open until January 1, 2005. Separate discumust be submitted for individual papers. To extend the closing daone month, a written request must be filed with the ASCE ManaEditor. The manuscript for this paper was submitted for review andsible publication on August 21, 2002; approved on May 29, 2003.paper is part of theJournal of Construction Engineering and Management, Vol. 130, No. 4, August 1, 2004. ©ASCE, ISSN 0733-93
2004/4-598–606/$18.00.
598 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT

Downloaded 09 Nov 2010 to 160.75.22.133. Redistributio

Moreover, contemporary computer-aided tools includingcharts or critical path method network charts can only reprethe construction schedule, but not the spatial features or theciated resource requirements. Visual representations of the pat different instants, including project progress and the statsite space usage, cannot be provided. Thus, in order to selemost feasible construction scheme as well as site usage lplanners can only gather information from design documentsapply their judgment and experience. It is apparent that thetential capability of computers could be further exploited.

During the past decade, previous research efforts havemade towards advanced four-dimensional~4D! planning modelby integrating three-dimensional~3D! visualization with the timattribute. Retik et al.~1990! studied the feasibility of using computer graphics in partnership with construction schedulingexplored the required functions. Zhang~1996! reported on a 3Dgraphical construction model. Williams~1996! designeddemand-driven 4D model for the generation of a graphicalstruction plan on the basis of simulation, visualization, and cmunication. Collier and Fischer~1996! demonstrated visual-bas4D modeling and scheduling in a case study of the San MCounty Hospital. McKinney et al.~1996! proposed a foudimensional computer-aided design~4D-CAD! tool with visualand communicative functions to facilitate the design procAdjei-Kumi and Retik~1997! applied the concept of virtual reaity to visualize the construction plan using a library-basedmodel. McKinney et al.~1998! demonstrated the capability4D-CAD models to identify construction problems prior to thactual occurrence. McKinney and Fischer~1998! studied the effectiveness of a hybrid 4D application using the contemposoftware Primavera, AutoCAD, Jacobus Simulation Toolkit,Walkthru. Zhang et al.~2000! developed a 3D visualizatiomodel with schedule data at the level of construction componKamat and Martinez~2001! presented a 3D visualization mo
depicting the entire process of a typical construction activity.
© ASCE / JULY/AUGUST 2004

n subject to ASCE license or copyright. Visit http://www.ascelibrary.org

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This paper also presents a 4D visualization model forstruction planning and site utilization by integrating a 3D gmetrical model with a project activity schedule. A distinct feaof this model is the annotation also of a construction activityits associated resources requirements: labor, material, andment. One of the major objectives of this work is to providflexible 4D graphical visualization capability that is also connient to use for short term replanning and communication, usfor a specific part only of the whole project, because this is orequired at site level. Other useful features for efficient site magement are also included, such as construction schedulefacilities layout, site workspace utilization, resources allocaand cost estimation. One overall research objective is to proour knowledge and understanding of the role for modern cputer graphics in enabling construction site managers to bdischarge their responsibilities.

Characteristics of 4D Visualization Model

The generation of this construction project 4D visualizamodel requires integration of a 3D geometrical model withassociated schedule of activities. Other computer-basedniques are also incorporated to enhance its capability to carruseful site management functions over different spatial andporal domains. The model provides a comprehensive site mament tool for construction managers during the building cycleenables visualized planning, linkage between the 3D geomemodel and the bar chart schedule, resource requirement anfor each activity, material allocation, and cost breakdown.

4D Visualization of Prospective Scenarios

The visualization of the 3D construction site status, the compwork, and the status of uncompleted work is displayed atspecified time by moving forward or backward on a timeline. Tis accomplished through the integration of the 3D geometmodel and the associated activity schedule for the construproject. It assists construction planners in making crucial dsions by enabling visualization of the details of the prospework at any specified time. A variety of scenarios with alternaconstruction sequences can be tested, and identification of ptial logistic problems is assisted.

Other Essential Site Management Functions

Through the linking of symbolic and graphical data, this moincorporates facilities assisting other essential site managefunctions—e.g., computing the resource requirements of diffactivities for labor, material, and equipment; estimating thecurred cost in any specified time period; and evaluating anding various construction plans through its knowledge base. Oall, this model assists a manager to improve resource allocduring the planning and management of construction work, athat is becoming more and more difficult to achieve nowada

Traditional Management Practice

A major impediment in the use of any new software is nonfaiarity. In order to reduce this effect, the traditional site manment representations of the construction schedule and site falayout are simulated in the 4D visualization model as far assible. Hence, drawings and bar charts are employed to rep
site plans and project schedules, respectively.
JOURNAL OF CONSTRUCTION ENG


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Bidirectional Data Exchange between 3D Model andSchedule

This model allows bidirectional data exchange between thgeometrical model and the project schedule. The user is grthe alternative to update the construction plan either throug3D graphical environment or through the conventional bar cscheduling environment. If the timing of a certain activitymodified graphically on the screen, synchronized adjustmethat activity will be made automatically to the bar schedule,vice versa. Furthermore, the evaluation of the resource reqment schedule will also be updated to achieve consistency.

Graphical Representation from Different Angles ofView

This model is able to represent components of the 3D mgraphically as viewed from different angles, because of thevision of a graphical user interface~GUI! and input data on thgeometry.

Architecture of 4D Visualization Model

In order to successfully integrate different components forstruction planning and management, an essential requiremthe 4D visualization model is the ability to identify and organvarious types of data. The algorithm for the model is mastructured to satisfy this goal. Another essential requirementconsistency of data within the 3D geometrical model, proschedule, and resources computations, in particular duringfication. Owing to the wide availability of microcomputers in soffices, this prototype model has been developed on a percomputer under the contemporary Windows platform. ViC11 is the programming development environment for thestruction processor as well as for the user interface. AutoCADbeen selected as the graphics tool. Microsoft Project hasadopted as the project scheduling environment and MicrOLAP as the data warehouse for the model. Fig. 1 show

Fig. 1. Architecture of 4D visualization model

architecture of the 4D visualization model. The prototype system

INEERING AND MANAGEMENT © ASCE / JULY/AUGUST 2004 / 599


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comprises six principal components that interchange datachronously through the dynamic data exchange facilities. Thtails of the components are listed as follows.

4D Visualization Module with AutoCAD ObjectARX

The 4D visualization module, being central to the prototypetem, undertakes various functions, including integration amoother modules, 4D representations, and practical site managoutputs. It comprises spatial representation via a 3D geomemodel that simulates the state of a project at a specific instogether with the temporal representation via its associated sule. The visualization output is produced as a series of grabased on the 3D geometrical model, numerical representatioattributes of building components, and the locations of temposite facilities, all as functions of time during the construction pcess. Dynamic changes to the visual attributes of the entitiethen represent progress in 4D states with advance of constrtime. In this context, a specific 4D state is defined as the grapdisplay of the project with visual and numerical attributes in aformat at a specified time. Moreover, this module enriches thstate with the annotation of other associated entities~labor, material, equipment, workspace, and cost! for onward processingresource evaluation, workspace analysis, and cost breakdow

Construction Processor with Visual C ¿¿

The construction processor, being the key instrument forchanging data, is responsible for providing a link between th

Fig. 2. Sample screen sh

geometrical model and the construction scheduling data for on-



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ward processing in the 4D visualization module. The construprocessor checks the data feedback from the 4D visualizmodule to ensure synchronization with the scheduling data bthe model regeneration results in any modifications. Moreovundertakes to represent construction activities symbolicallyfunction of time, to compute the resource requirements foractivities, to estimate associated workspace and temporaryties, and to evaluate costs for any activities.

3D Geometrical Model under AutoCAD Environment

In this prototype system, AutoCAD is employed as the grapprogramming environment by a construction planner whenerating a 3D geometrical model of the project. It is representevarious graphical construction components or other entitielated to construction activities, which are broadly grouped uthe three categories:~1! structural elements;~2! operational objects; and~3! temporary facilities. Structural hardware elemeusually on the basis of their relative locations, are further clfied under different subclasses of building components sufloor, beam, column, slab, wall, and so on. Operational obgraphically represent the progress states of construction actfor a particular structural component. Typical examples of optional objects include formwork erection, falsework installatsteel fixing, and concreting, to name a few, and they arerepresented in the 3D model by a different image pattern sua variety of graphical textures. Temporary facilities such as

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Bar Chart Scheduling with Microsoft Project

Microsoft Project is used in this system to display a bar cscheduling environment that links the temporal relationsamongst various construction activities from start to compleof the construction project. This module is the main data sofor the generation of the bar chart project schedule. Essentiainclude the duration of a specific construction activity, the cmencement time and end time of an individual activity, sequing data amongst the various activities, and symbolic sitedetails.

Data Warehouse with Microsoft OLAP

Because an enormous amount of data is generated in the 3Dmetrical model, including scheduling and resource allocationnotations, data manipulation is crucial to the success of thvisualization system. In this study, a data warehousing techhas been adopted to manage the database. It represents theedge base that encompasses all the working details and contion management on the project. The integration of graphicalwith different nongraphical scheduling data is attained basetheir spatial-temporal relationships and the dynamic exchaThe data warehouse provides a data structure for bidirec

Fig. 3. Sample screen showing inpu

data flow between the construction schedule and resource data



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management features within the 4D model. Microsoft OnAnalysis Processing~OLAP! is employed as the data warehoing software~Chau et al. 2003!.

User Interface with Visual C ¿¿

An interface allows the user to specify all planning parameand acquire the output results from the system. The useevaluate the prospective construction progress during thening process through the interface. In this prototype sysgraphical user interfaces, consisting of layers of display scand pop-up windows, are used for message transfer, resultthe greater simplification of data handling. The user has coover the sequence of actions during the planning process sto conformance with knowledge modules that store certainristic rules on construction technology.

Algorithmic Process

The algorithmic process in the 4D visualization system is divinto two major steps:~1! 4D visualization based on the data inpand ~2! validation of data feedback from the 4D visualization

4D Visualization Based on Data Input

The 3D geometrical model is based initially on the geometdata input of the construction project. After this, the construc

of various elements and their relationships
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resentations of all structural elements and temporary site facinvolved in the 3D geometrical model to corresponding symbrepresentations.

The construction activities involved at different levels,gether with their interrelationships for various structural comnents, are retrieved from certain established or heuristic mestatements, and the subsequent construction technology detion is then stored in a knowledge base. Moreover, based oknowledge base, adequate temporary facilities are automaadded on the site layout plan.

The intermediate output acquired automatically at the enthis stage is initial scheduling data, which is then transferredtomatically into the Microsoft Project environment for manipution and validation before the generation of the bar chart schfor the project. The user is allowed to refine and even drastialter this scheduling data, so as to represent the intendedconstruction plan. The data is subsequently transferred backconstruction processor for the ultimate compilation and gention of the 4D visualization model, by integrating the componrepresentation data with this initial plan. The dynamic visuatribute of an individual component representation entity is emized in terms of a numerical expression as a function of tThree types of visual attributes are available here:~1! visible; ~2!visible plus certain image patterns of other activities; and~3!invisible. The construction processor then provides the featueach construction entity in accordance with the aforementiknowledge base on construction technology.

This ‘‘process representation’’ process expresses the sptemporal relationship between the 3D geometrical model an

Fig. 4. Sample screen showing da

scheduling data, in order to generate the 4D visualization model.



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The construction processor determines the visual attribute ofstructural component or site facility for display of the 3D gmetrical model against the time expended during daily operof the project, on the basis of the process representation.

It should be noted that the construction processor is the kevaluating whether a structural element is visible, visible plspecific operational object, or invisible, and whether a tempofacility is visible or invisible at a specified time. Furthermore,construction processor integrates graphical and nongraphicawith construction annotations for the generation of the 4D valization model.

Validation of Data Feedback from 4D Visualization

If any modifications are made to the 4D state via the grascreen in the 4D visualization model, it is important to ensurethe scheduling data is also updated in a synchronous mandifficulty has been encountered in achieving this reverseflow. It comes from the intuitive limitations of an individual 4state, which cannot incorporate the activity relationships antemporal attribute at the same time. A new algorithm withintroduction of certain operational attributes has been devehere to overcome this difficulty.

In this algorithm, the activities displayed in a simulation of4D state representing the status for a specified time can bvanced, postponed, prolonged, shortened, or paused, via thand adjustment of the corresponding visual attributes. Thrthese operations, any modifications to the 4D state can bflected by updating of the scheduling data. A few assump

ut of segments and associated scheduling
ta inp
have been made underlying the development of this new algo-



Fig. 5. Sample screen showing some predefined templates of construction activities

Fig. 6. Sample screen of 4D visualization linking 3D geometrical model with schedule

JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / JULY/AUGUST 2004 / 603

Downloaded 09 Nov 2010 to 160.75.22.133. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.org

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rithm, with a view to reestablishing the temporal attributesthe activity relationships after the 4D state has been adjuThey are listed as follows:• The total numbers of activities are not affected;• Activities happening prior to the modification timeline are

altered;• The orders and relationships amongst different constru

activities are not affected;• The connectivity time between successors and predecess

all activities are not changed; and• In case any temporal attributes of an activity have been m

fied, the user is required to enter new values of the actduration, commencement/completion/connectivity time,all its successors and predecessors.The validation of data feedback from the 4D visualiza

model should also adhere to these assumptions. Once anposed modifications are entered via the GUI to the 4D state i4D visualization model, the construction processor will determwhether or not the request is legitimate. The construction prosor will adjust the process representation and the schedulingrelevant to the associated activities or temporary facilities onbasis of the construction technology knowledge base only irequest is considered legitimate. The temporal attribute of ativity will be adjusted. The construction processor will thendate all the following activities that are affected. At the satime, the bar chart schedule under Microsoft Project will bedated synchronously. Moreover, the construction processouse the updated scheduling data to regenerate both a 4D vization model as well as a process representation. However,

Fig. 7. Sample screen

modification is considered illegitimate, the construction processor



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will revert to the original 4D visualization model, meaning tthe modification is not successful.

Verification and Validation of 4D Visualization Model

This prototype system was applied to the Tradeport LogCenter—a three-story warehouse building site—during the aconstruction of the project, in order to verify and validateperformance in real practice. The construction period forstructural works was from January to October 2002. Althoughbuilding was nominally of three stories, each story was of doheight with mezzanine floors. Thus, together with the roostructure, the building had the height of a typical seven-sstructure. The client, The Hong Kong Land Company Limite~amajor property development company in Hong Kong! and thecontractor, Gammon Skanska Limited~one of the largest in HonKong!, had entered into the contract on a guaranteed maxiprice basis. The contractor was involved early in the preconstion period and had made contributions to the design. The ptype 4D visualization system was employed throughout thestruction process of this project to evaluate the data represenadequacy and also the effectiveness of the system.

The data input and output are best demonstrated in termsome sample screens for this practical application. Fig. 2sample screen showing data input of a building story. Fig. 3sample screen showing input data of various elements andrelationships. Fig. 4 is a sample screen showing data inpsegments and associated scheduling. Fig. 5 is a sample

ing 4D state being updated
show
showing some predefined templates of construction activities. Fig.



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6 is a sample screen of a resulting 4D visualization linking ageometrical model with a schedule. Fig. 7 is a sample scshowing a 4D state being updated. Finally, Fig. 8 shows a sascreen of the output 4D visualization on a projected date.

In this application work, comments made by the site staff walso incorporated, resulting in substantial improvement inpracticality of the system. Moreover, the verification and valtion did demonstrate the real application of the 4D visualizamodel in short-term site replanning activities. The experiegleaned from this verification process was delineated in Aet al. ~2004!.

Conclusions

In this paper, a prototype 4D visualization model has been doped and implemented with a view to overcoming problemscurred in conventional construction planning methods and icorporating practical site management features. Thisvisualization model, which links the 3D geometrical model wscheduling data, comprises the activity schedule, associatedcation of resources, and layout of site facilities at any projeinstant. There are many potential benefits of a 4D visualizasystem, including facilitating site planning and management,dicting the occurrence of any potential site problems, and strlining the site management practices. Moreover, the advaments in computing technology have assisted in this wresulting in a user-friendly, comprehensive, and integratedmanagement tool. It is believed that 4D visualization will hstrong potential in construction planning and management

Fig. 8. Sample screen of

cesses.



Acknowledgment

This research was supported by the Research Grants CouHong Kong~PolyU5060/99E!.

References

Adjei-Kumi, T., and Retik, A.~1997!. ‘‘A library-based 4D visualizatioof construction processes.’’Proc., Information Visualization Conf., In-stitute of Electrical and Electronics Engineers, Piscataway, N.J.,321.

Anson, M., De Saram, D. D., Zhang, J. P., Chau, K. W., and Wang,~2004!. ‘‘Trial of 4D simulation software on a medium scale buildconstruction site.’’Constr. Manage. Econom.,in press.

Chau, K. W., Cao, Y., Anson, M., and Zhang, J. P.~2003!. ‘‘Applicationof data warehouse and decision support system in constructionagement.’’Autom. Constr.,12~2!, 213–224.

Collier, E., and Fischer, M.~1996!. ‘‘Visual-based scheduling: 4D moeling on the San Mateo County Health Center.’’Proc., 3rd Congreson Computing in Civil Engineering, ASCE, New York, 800–805.

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