KSCE Journal of Civil Engineering (2010) 14(6):803-814 DOI 10.1007/s12205-010-0960-4
Construction Management
www.springer.com/12205
Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code Leen-Seok Kang*, Hyoun-Seok Moon**, Seo-Young Park***, Chang-Hak Kim****, and Tai Sik Lee***** Received August 12, 2009/Revised January 12, 2010/Accepted February 11, 2010
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Abstract Current 4D CAD systems can perform basic functions to construct a 4D simulation to visualize a construction schedule. One important function is to link the schedule to a 3D object because it is the most basic and essential process necessary to create a 4D simulation. Though the link process in existing systems is still somewhat complicated, it can be simplified by changing the information structure of the system. Because the 4D system includes the schedule, 3D objects, and 4D simulations, the database of the system stores various information. Accordingly, information management in a 4D system is an important factor to serve the user's convenience and to simplify the link between a construction schedule and drawings. This study presents an effective information management methodology, an improved 4D system, using Work Breakdown Structure (WBS) as an information center. The artificial link process to generate a 4D simulation can be simplified by using the same WBS code for both schedule and drawing information. The suggested methodology was applied in a new 4D CAD engine developed in this study and verified by running practical data from a gas plant and a civil engineering project. The developed system enables project manager to generate a 4D simulation at WBS code level. This function can be a useful tool and a new approach to visualize schedule data in a large project. Keywords: 4D CAD system, virtual reality, Work Breakdown Structure (WBS), schedule, 3D object ···································································································································································································································
1. Introduction Visualization of construction schedule information is an important function in practical project management using Information Technology (IT) tools. Currently, a number of drawing programs use 3D objects and most construction projects use a computerized scheduling tool. In this environment, a 4D system is a logical solution for visualizing schedule data. A 4D system for construction management requires a tool that will represent the stages of completion of construction work with 3D object type linked to a construction schedule. Because a 4D system includes schedule and drawing information, the database of the system consists of various kinds of information. Accordingly, information management in a 4D system is an important factor both to serve the convenience for user and to simplify the link environment between the construction schedule and the 3D drawing. Our paper presents an effective information management methodology using the Work Breakdown Structure (WBS) system as an information center in a 4D system. In the earliest 4D systems, data for schedules and drawings
were all imported from external software applications and mapped to simulate a 4D image. Their successor systems had built-in functionality for the generation of schedule and drawing data to simplify data mapping, but only to a certain extent. Most of the current 4D systems, such as CSA (2004), VirtualSTEP (2002), and VTT (2006), require many hours of interfacing work to link a 2D schedule to 3D drawing data for a 4D simulation because that information is managed by a separate code system in the simulator (Kang et al., 2004). At present, to make 4D simulations, interfacing is time-consuming and unavoidable. If an improved information structure can be applied to the system, it can reduce the time expended in the linking process. Other systems, such as Commonpoint (2006), Fischer et al. (2001), Bentley Systems (2005) and Intergraph (2005), also have many helpful functions to generate a 4D simulation. They are focused on building projects that consist of artificial and vertical elements. And the detailed process consists of a basic function to visualize a 4D simulation. That is, although the special importance of those systems to visualize an activity schedule, an effective technology of information management within the system
*Member, Professor, Dept. of Civil Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660-701, Korea (E-mail: Lskang@ gnu.kr) **Member, Ph.D., Dept. of Civil Engineering, Gyeongsang National University, Jinju 660-701, Korea (Corresponding Author, E-mail:
[email protected]) ***Ph.D., Dept. of Civil Engineering, Gyeongsang National University, Jinju 660-701, Korea (E-mail:
[email protected]) ****Member, Associate Professor, Dept. of Civil Engineering, Jinju National University, Jinju 660-758, Korea (E-mail:
[email protected]) *****Member, Professor, Dept. of Civil Engineering, Hanyang University, Ansan 426-791, Korea (E-mail:
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has not yet been devised and ineffective information management means a complicated linking process and low practical applicability. Accordingly, an improved methodology is needed for information management, including a link process between schedule and 3D object. That is, the ease of mapping schedule data to drawing data can be a key factor for fast, practical applications of a 4D system (Kang et al., 2006). In simulation research, Dawood et al. (2003) attempted to link information classification system with 4D system. The research of Dawood et al. (2002) and Gao et al. (2005) sought to manage space conflict problems and explain the advantages of a 4D system. This study proposes a new approach using WBS code as a common information nexus in a 4D system, so that WBS becomes the information center for managing all data in a 4D system. Accordingly, it is possible to generate a 4D simulation by each code level in WBS, a new approach to improve the information structure of a 4D system and to increase practical applicability of visualized schedule data. Finally, this study develops a novel 4D CAD engine using new methodologies. The engine is verified by using existing data from a gas plant and a civil engineering project.
2. Methodology to Use WBS as a Central Interface Scheme in a 4D CAD System 2.1 Configuration of WBS for a Construction Project The levels, or facets, of WBS consist of elements, space, and facility (Fig. 1). The element facet contains detailed information to construct a dependent structure; the space facet includes those dependent structures necessary to construct a facility; and the facility facet is final whole products incorporating relevant space items in a project. For example, a highway facility consists of spaces, such as bridge 1, bridge 2, tunnel 1, and tunnel 2, and a bridge space consists of element items, such as abutment, pier, and slab. In this study, to adopt a standard WBS code system, we had to resolve some problems with existing construction information classification systems, such as Crawford et al. (1997) or CSI/CSC (1988), which were analyzed and an enhanced classification code was suggested. The analyzed results for existing code systems are explained in Kang and Paulson (1998, 2000). Since this research is focused on a data interface scheme of a 4D system, the detailed configuration approach of the information classification system for construction projects is not described.
Fig. 1. Levels of WBS
Fig. 2. Example of Organization for Project WBS Code (Highway Project)
Because each WBS facet, facility, space and element, consists of separate files in the system, a project WBS can be organized by selection of each code in those facets. Fig. 2 shows the process for organizing a project WBS through the selection of code in each of the three facets. 2.2 Concept of WBS as an Information Center in a 4D System The basic function of a 4D system is to generate a simulated stage-by-stage version of the completed project by interfacing the construction schedule and 3D drawing data. Notably, the construction schedule and drawing data for 3D object creation are key inputs to the simulation work. In that context, a code structure that can be used to manage such data systematically in the database of a 4D system is necessary as an information center. This study assumes WBS code to be the information center for all inputs and outputs of a 4D system. As depicted in Fig. 3, the WBS codes are linked with schedule data and corresponding 3D object as common code for mapping all data. Generally, key functions of a 4D system include a 3D modeling engine to configure of the 3D object, a scheduling engine for schedule management, a 4D simulating engine for mapping the 3D object to schedule data to simulate construction progress in 3D type, and a virtual reality (VR) engine to generate the animation of the completed 4D simulation. In this study, such major functions are linked to each other in reference to WBS (Fig. 4) where the WBS generator is responsible for generating the project WBS applicable to a specific project when the 4D system is started. Once generated, the WBS works as the information center for all 4D simulation functions of the project. 3D objects in generic CAD files are configured only by layer or color and not assigned detailed attributes. In this research, common WBS code values were assigned as attributes of 3D objects by way of the hypertext function of AUTOCAD so that a 3D object could be summoned when the WBS generator requested a WBS code. The merit of the proposed attribute integration is that objects that have the same layer or even different types of layers are grouped together as long as they are mapped to the same WBS code. In other words, a 3D image by activity schedule can be generated by work area or activity level using common
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Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code
Fig. 3. Mapping Process between Schedule and 3D Object using WBS Code (Kang et al., 2007)
Fig. 4. Information Structure in WBS-aided 4D System
WBS code. All modules in a 4D system have their own data structures, and they also have individual key fields of WBS code for each data structure. By this key field, all functions in each module, such as the 3D modeler and schedule modeler in Fig. 4, can be operated using WBS code.
3. Mapping Process between Schedule Data and 3D Object Using WBS Code 3.1 Data Interface for Mapping Simulations Using WBS Code Much information, such as schedule data and 3D objects, is needed to make a 4D simulation. Currently, many 4D systems are being developed and some can be applied to construction projects. Their practical applicability is not high because it takes excessive time to link schedule data and 3D objects to complete a 4D simulation of a project and requires much preparation of initial data, such as 3D objects, for each activity. Another problem is insufficient functions. The current 4D systems cannot Vol. 14, No. 6 / November 2010
yet provide the results for progress control and earned value management, as is found in traditional scheduling software. To improve the practical application of a 4D system, it is necessary to simplify the link process and reduce the required initial data. The existing link method is focused on the connection of imported data from scheduling software and a CAD system. That is, schedule data is imported using activity code from scheduling software, such as P3 and MS Project. Plus, to create a 3D object, drawing data created by a separate 3D CAD tool is configured using a different naming convention and stored. Schedule and drawing data stored by the aforementioned method must be cross-interfaced for 4D simulation. To that end, users must individually map activities listed in the schedule data to corresponding 3D drawing data using the 4D tool. To make a 4D simulation file in those systems, schedule and drawing data are generated by activity code and drawing code, respectively, then those data need to be linked to generate a 4D simulation in an additional linking process. If there were a common code system, such as a standard WBS, that could be used for both schedule and drawing data, the link process could be simplified because all data in the 4D system is generated by a common WBS code. Elimination of the need for data mapping can significantly reduce excessive workloads in initial data input, which is an important drawback to current 4D systems. This study proposes that a standard WBS be stored in advance as a library file within a 4D system and all functionalities of the system be operated in reference to the WBS code. To configure schedule information in a schedule management module, schedule data are created directly in reference to a pre-defined WBS code and activity list. In terms of drawing data configuration, too, drawing an object corresponding to library WBS code is stored in advance. As the approach described above stores both schedule and drawing data in reference to common WBS codes, they are mapped to each other automatically in a 4D simulation.
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Fig. 5. Data Interface of 4D System using Common Code
Fig. 6. Multiple Link Function between Schedule Data and 3D Object
Fig. 5 shows a data interface scheme utilizing common WBS code. The detailed link procedures in this suggested system are as follows: a) use a standard WBS as a library file in the 4D system; b) generate project WBS code by using library WBS codes; c) compose schedule data using WBS code as an activity list; d) compose 3D object data using same WBS code in schedule data; and e) generate the 4D simulation using WBS code. Current data interface schemes do not present common references to map the schedule and drawing data in advance. Therefore, users are required to configure the schedule and drawing data individually, then map them separately to create the mapping code. This slows system start up in terms of initial data input and overall 4D functionality. The proposed data interface in Fig. 5 uses WBS code from the beginning of schedule and drawing data input, eliminating the need to map them to each other following data configuration. This simple process can reduce the initial input time to make a 4D simulation, and is a significant improvement over the current systems’ link process between schedule and drawing data.
mapping methodology of multiple link function (1:n link system). If schedule data are used for a summarizing activity at a higher level of the WBS, they can be collectively linked with many 3D objects for detailed activities of the schedule data in a 1:n link method. In Fig. 7, the user preferentially selects three 3D objects for a multiple link. Fig. 8 shows the screen on which selected 3D
3.2 Multiple Link System between Schedule Data and 3D Object In existing 4D systems, the link process links individual schedule data sets to individual 3D objects. In this process, the user has to individually link all schedule data that correspond to individual 3D objects, which requires much time and effort. To improve on this, the proposed system in this study is able to compose multiple link function by work element using WBS code in the 4D system. In multiple link function by work element, 3D objects are selected in multiples of the number n. Selected objects link schedule data in a descending order of priority of sequence. That is, each selected 3D object has an independent schedule code, but in case all these 3D objects are gathered together collectively, they become one composite schedule data and must be mapped by a multiple link function. These examples can be also used when many schedule data sets are gathered together to be expressed in one 3D object. Fig. 6 shows a − 806 −
Fig. 7. Selection of 3D Objects for Multiple Link
Fig. 8. Selection of Schedule Data for Multiple Link KSCE Journal of Civil Engineering
Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code
objects in Fig. 7 are linked with one schedule data set in the 1:n method by a 4D viewer. In the case of a large construction project, it consists of many schedule activities and 3D objects to generate 4D simulations. The time required for the linking process can be reduced in a multiple link system because frequent mouse activities for a 4D simulation link can be simplified by using the WBS code that now is the common code system between schedule data and a 3D object.
mapping process is completed by linking a selected 3D object to the schedule data. Fig. 10 represents a detailed process for mapping a 3D object in a schedule data-oriented method. Schedule data are selected from the WBS code list, then the corresponding 3D objects in a 3D window are dragged by mouse to the selected schedule data, then the link status is confirmed by moving the mouse in the 3D window. The 3D object that was linked with the schedule data has a WBS code, as shown in Fig. 10.
3.3 Schedule Data-oriented Mapping Process In a 4D CAD system, the mapping process between schedule data and 3D object can be divided into the method that links the corresponding 3D object based on the schedule data and the method that links the corresponding schedule data based on the 3D object. The existing systems are usually composed of one mapping process. It is necessary, however, to have a dual application mapping process to accommodate the complex characteristics of construction projects. That is, in a link system of 3D objects based on schedule data, it is currently difficult to make individual selections of the corresponding elements for the link when parts of the facility are complex. Considering these limitations, in this research, a link system that can handle both methods is provided in a 4D system. In a schedule data-oriented mapping process, as in Figs. 9 and 10, the schedule data of the corresponding 3D object is preferentially selected by the WBS code system. Selected schedule data are temporarily stored in the interface board for later linking and the
3.4 3D Object-oriented Mapping Process The 3D object-oriented mapping process has a link process opposite to the schedule data-oriented process. While schedule data are an information center in the schedule data-oriented mapping process, the 3D object becomes core information in a 3D object-oriented mapping process. That is, as shown in Figs. 11 and 12, after a 3D object is selected, corresponding schedule data are selected and linked in the interface board. Fig. 12 represents a detailed process for mapping schedule data in a 3D object-oriented method. A 3D object is selected in the 3D window, then the corresponding schedule data in WBS code is dragged to the selected 3D object. The schedule data, which has a WBS code, is linked with the 3D object. In this study, the mapping process between schedule data for time management and a 3D object for drawings management is a link system capable of moving in both directions, such as from schedule data to 3D object and from 3D object to schedule data. This function is expected to reduce time and effort in the
Fig. 9. Data Structure in Schedule Data-oriented Link System
Fig. 11. Data Structure in 3D Object-oriented Link System
Fig. 10. Mapping Process of Schedule Data-oriented Method in 4D System Vol. 14, No. 6 / November 2010
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Fig. 12. Mapping Process of 3D Object-oriented Method in 4D System
mapping process, which has been considered such a problem in the existing 4D systems.
4. Development of 4D CAD Engine Using WBS Code 4.1 Generation of a Standard WBS Library File In the proposed 4D system, the WBS code is used as a standard library file so the project manager can generate a WBS tree of each project by using the library WBS. The WBS generator is a module to organize a project WBS in the developed system. Fig. 13 shows an example of how to complete a project WBS using built-in WBS facets in a WBS generator. Once a facility code is selected for the facility facet, the space codes that can be mapped to the selected facility code are differentiated by color in the space facet (Fig. 13). Likewise, if a space code is selected, the element codes that can be mapped to
the selected space code also are indicated by color. Next the user selects element codes. After the selection process for each facet is finished, the completed project WBS is automatically generated (Fig. 13). Visualization of WBS code is also a helpful way for a nonexpert to understand the layout of a whole project. Fig. 14 represents a visualized WBS tree of the project WBS code by using StarTree software (Inxight, 2006). The levels of the WBS tree are represented by branches of different colors. The 3D object for the selected WBS code can be directly identified in the WBS generator because each code is linked to a 3D object. This example shows that the 3D object, a shaft bunker (code name 160 Shaft Bunker in Fig. 14), in a gas plant facility can be directly viewed by its link using WBS code. Accordingly, it is possible to visually confirm a 3D object of a selected WBS code at any level through all WBS codes. 4.2 Configuration Function of 4D Simulation by WBS Level Based on the previously mentioned link methodology between schedule data and 3D object data, this study develops a new 4D system that realizes the 4D simulation. The name of the developed system is V-CPM (Virtual Construction Project Manager). The source program of V-CPM is composed in JAVA and visual basic
Fig. 13. Generation of Project WBS using Library WBS File (Gas Plant Project) − 808 −
Fig. 14. Visualization of WBS Code in a 4D System KSCE Journal of Civil Engineering
Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code
language. In this research, a user can selectively realize 4D simulations of structures the user wants by work level or element item, each of which is constructed by applying the WBS-centered link system for 4D simulation. If a previous 4D system used a simple code system, not a code level as sophisticated as WBS, the project manager can visualize just one work item for the only selected code, as shown in Fig. 15, which represents the construction process of a butane cavern structure for a gas plant project by activity schedule. A project manager can confirm the work process of the butane cavern structure by its schedule, but
Fig. 15. 4D Simulation using a Specified WBS Code
he cannot confirm related structures or the whole work process of the gas plant by code selection. However, if a 4D system uses a WBS with code levels, it is possible to generate a 4D simulation by selected work level, as in Fig. 16, which shows the process of composing a 4D simulation by WBS code level. The project manager can check the detailed 4D simulation for work process of the butane cavern structure of the gas plant or generate a 4D simulation for whole plant construction by simply selecting the WBS code. The left panel of Fig. 16 shows whole project WBS code and the right side shows the 4D simulation process resulting from the selection of WBS code level from the left side. This partial 4D simulation by code selection by WBS level is a useful function utilized when partial 4D simulation for intensive management is desired and the project scale is very big. The code name at the highest level of this project is SK-GAS. Using the WBS-centered system, if this code is selected, the construction process of the whole project is generated in the 4D system. The code names at the second level are butane cavern and propane cavern. So, as in Fig. 16, SK-GAS is simulated by two main spaces that consist of the butane cavern structure and the propane cavern structure. Additionally, the two main spaces can be separately simulated by code selection. The butane cavern structure consists of six elements, including access pipe, water curtain pipe, connection pipe, and so on. In Fig. 16, codes 120 (water curtain pipe) and 150 (cavern) (both bars blue) show the simulation process for those activities at the third, or element, level. Partial 4D simulation by the selection of the desired WBS
Fig. 16. 4D Simulation using WBS with Code Level Vol. 14, No. 6 / November 2010
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Fig. 17. Link of Simulation Objects using the WBS Generator
code is possible on any level of a space item or an element item. And if the project manager selects a WBS code at the upper level, it is possible to bring all work items together at a lower level. As described for the left side of Fig. 16, 4D simulations of specific spaces (for example, butane cavern and propane cavern) can be realized in this way. If the user drags only the parts the user wants, the schedule information can also be expressed only in the schedule of the lower level activities in the selected schedule and generate a 4D simulation only of them. Therefore, it is possible for a project manager to control visualized schedule data intensively by element or work zone. Because a 4D simulation is generated by WBS code level, if, say, the highest-level code of a bridge is selected, a 4D simulation of the entire bridge is produced. Similarly, the 3D object of a pier element is created when pier code is selected. Schedule data can be also be generated in the same format as a 3D object because all functions of the system operate with reference to the common WBS code. In other words, schedule data can be selectively generated by activity level to meet the specific requirements of the project manager. Fig. 17 shows the data interface of a 4D system in which all data in the schedule, 3D objects, and 4D modeling engines are linked by the WBS generator. The VR engine can also generate animated files using WBS code. In the proposed 4D system, if the project is highway construction, the VR engine can show a virtual, lifelike traffic situation for the selected WBS item.
Fig. 18. Identification of WBS Code in 4D CAD Viewer
If the project consists of many kinds of detailed elements, it can be difficult to identify which elements in a main structure are linked with schedule data or WBS code. At this point, it is necessary for a project manager to identify the link status for each 3D object in the 4D system. Because all 3D objects are linked by WBS code, if a user uses a mouse to drag a specific object, WBS code of the selected object is shown on the screen (Fig. 18). Thus, it is easy to find the unlinked objects in a project. This function is especially important when the project consists of complicated elements, as in a plant project. 4.3 Comparative Analysis of Link Process of Schedule with 3D Object The link system by WBS proposed in this study has a simplicity in link process for a new project. In case of a new project, schedule data and 3D object should be imported from schedule software and CAD tool, and then they are mapped to make 4D object by a link process. In V-CPM, schedule data can be selfgenerated without any imported file because the scheduling function is built in the system. Because each activity name in scheduling function uses a WBS code which is a built-in database, the additional link step of schedule data can be shortened. The 3D object and CAD layer directly can be linked to the schedule data. Comparing with the current systems, the link process between schedule data and 3D object is more simple in VCPM because the schedule data needs not import and map with a link code. The detailed link process between V-CPM and current system can be compared in Fig. 19. Schedule data and 3D object should be imported to generate a 4D object in all 4D systems. WBS code is used as a common code system for linking those information in V-CPM and the other system uses activity name and 3D object name for a link tool in current system. That is, if an activity name is same with 3D object name, the activity is linked with the same 3D object. It is difficult for project manager to confirm schedule and 3D data of a selected object because the current systems do not use a link code for mapping schedule and 3D object in current system. However, this process can be easily
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Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code
Fig. 19. Comparison of Link Process between V-CPM and Current System
confirmed in V-CPM. If WBS code is used for a common code in 4D system, 4D object can be simulated by each WBS level and all of information in 4D system can be simply managed by WBS code. On the other hand, 3D object is linked with entity level or 3D layer level in current system. Accordingly, it is difficult for project manager to directly make a 4D object in activity level. 4.4 Simulation Function of a 4D System for Civil Engineering Projects In civil engineering projects, such main activities as earthworks, bridge work, and tunneling progress horizontally in a wide work area and at the same time, construction of bridge pier structures progress vertically. When compared to a construction project that is mainly vertical, for a bridge, these points need a 4D simulation technique in which it is possible to have both horizontal and vertical realization to increase the degree of visualization based on the activity schedule. Different from 4D simulations of existing building projects, automatic simulation technology of a triangulate network is required to express the natural topography at the time of 4D visualization of linear civil engineering projects. That is, since 3D objects are required for the 4D simulation of a building project, and all are composed of artificial elements that have no Vol. 14, No. 6 / November 2010
relationship to natural topographical conditions, the composition of a 3D object can be expressed only with information on general attributes, such as length, thickness, area, and shape, while most of construction items for civil engineering projects consist of many earthworks and the completed status of these earthworks also must be visualized according to a predetermined activity schedule. One essential function in a 4D system for civil engineering projects is the 4D simulator that links 3D object with the activity schedule (Fig. 20). Because the 4D system should visualize natural topographical data, the 4D viewer includes triangulate network data represented by white lines on a black ground, as in Fig. 20, which shows an integrated function screen of a V-CPM. The layout consists of a 4D simulation (in upper part), WBS code (on right side), and schedule information (in lower part). In the existing 4D systems, after using outside tools for schedule and 3D object generation, a 4D simulation is generated using a linking tool. In V-CPM, the 4D system can compose the schedule and 3D objects without outside schedule and CAD tools. Therefore, 4D simulation can be produced using only the VCPM. In this new system, the 4D simulation the user wants can be selected by work level or element item using the WBS-centered link system, and the additional link process of schedule and 3D
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Fig. 20. Composition of Basic Functions of 4D CAD Viewer
object can be omitted. For the composition of schedule information, the V-CPM generates schedule information based directly on WBS code and the names of the works that are loaded in advance. At the time of utilizing drawing information, the 3D object is also being saved in the system. Because schedule and 3D objects are saved centering on the same WBS code, it is the system that is automatically linked without additional link work to generate a 4D simulation. In Fig. 20, the right upper side shows the process of generating
a 4D simulation for construction items of a bridge section after dragging bridge code from the library WBS code. Also, the right lower part shows the function for the user to manually simulate the completion status by dragging with a mouse a 4D simulation of the selected WBS code by specified period. Fig. 21 shows a visualization process where the selected objects can be simulated using only the WBS generator. That is, if he wants to simulate the code without a 4D viewer, it is possible for a project manager to identify the WBS code for a construction
Fig. 21. Selective Simulation of 4D Object for Bridge Activities − 812 −
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Improved Link System between Schedule Data and 3D Object in 4D CAD System by Using WBS Code
process, as shown in the lower part of Fig. 21. Also if, say, the tunnel code is selected, the construction process of tunnel work can be simulated by its activity schedule. The information-centered 4D system can consistently simulate completed status integrating 3D objects with schedule data at any level of WBS code. When a pier of a road bridge corresponding to an element facet of WBS code is selected for simulation in a 4D viewer, the 3D drawing is displayed only for the pier. If a code of road bridge is selected at the highest level in the space facet, activity progress compared with the schedule of the bridge as whole is displayed in 3D type. If the user chooses, if a highway item is selected at the top level of WBS code, the whole project progress compared to schedule can be generated in 3D type. Accordingly, those functions enable a project manager to visually control the project at any management level and the 4D system, improved by these new functions, can be an effective decision-making tool.
5. Conclusions Among various kinds of information in a construction project, construction schedule management requires specific visual information. However, at present, schedule information is still generated by traditional scheduling software only in terms of numeric values, failing to provide an efficient aid to project decisionmakers. This research proposes an approach to enhance information management in 4D systems. The summarized results follow. Concept of a common information center was used to integrate all data management in a 4D system. WBS code was used for the common information center and all discrete functions of a 4D system were referenced to the WBS code as their key fields so that all data stored in the 4D system could be managed by activity level. The advantages of this concept were validated in developed system implementation and proved capable of improving the performance of current 4D systems. At present, the most current systems are not capable of simulating completion status on facility, space, and element levels as users require. By developing a WBS-based data interface, this research enabled 4D simulation across different work levels. The study also describes a methodology for using WBS as an information center to link schedule and 3D objects and a new 4D simulation engine with the link system was developed and verified by actual objects from a plant project. The developed system was also verified using an existing civil engineering project that consisted of earthworks, bridge, and tunnel. Though the actual cases that use WBS code were verified in limited projects, the utility of the new 4D engine was ascertained by facilitating schedule management at each level. As the new 4D system generates 2D schedule, 3D objects, and 4D simulation data at different WBS levels, a project manager can obtain visual schedule information and monitor progress status of 3D objects by management level. This means that the 4D CAD tool can be used as an effective decision-making aid throughout a project. The main user group will be a contractor Vol. 14, No. 6 / November 2010
for the application of the suggested 4D system because the main functions in 4D system are focused for the construction phase. And the suggested new approach for link process is also focused in simulation of construction phase. To further enhance the usefulness of the methodology proposed herein, standard common WBS code for each facility should be further enhanced and system functionalities focusing only on 3D generation of 4D simulations of construction progress need to be further diversified.
Acknowledgements The authors would like to thank the Ministry of Construction and Transportation of Korea for financially supporting this research under 2004 and 2006 R&D programs (Virtual Construction System).
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