- Email: [email protected]
Visual simulation of construction projects on a microcomputer
SIMULATION
PRACTICE = THEORY
ELSEVIER
Simulation Practice and Theory 2 (1994) 77-90
Visual simulation of construction microcomputer Z.B. Harun
a, G. Singh
projects on a b*
a Department of Civil Engineering, Universiti Malaya, Kuala Lumpur, Malaysia b Department of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom Received 1 October 1993; revised 1 March 1994
Abstract Under the Microsoft’s Windows environment, Drafix CAD, MS Project, Visual Basic and Q + E Database/VB packages are integrated. This integrated software is able to show the step by step progress of the construction work in compressed time on the computer screen under the Visual Basic environment. The user is allowed to view the project in the bar-chart or network modes under the MS Project environment. This software opens up a new possibility of linking project planning with project design/visualisation in the microcomputer environment. The approach is demonstrated to be feasible and worthy of further development for the benefit of designers and project managers as well as site engineers. Keywords:
Animation;
CAD; Construction;
Logistics;
PC; Projects;
Simulation;
Visualisation
1. Introduction It is generally accepted fact that visually presented information is more easily understood and absorbed than verbal one. Also, visual material instils more confidence in the audience; as the saying goes “Seeing is believing”. This work utilises this in combining low cost visual tools on the microcomputer with overall construction projects scheduling and planning tools. In comparison with the manufacturing industry, the construction industry is slow in utilising the available computer hardware and software. This includes the areas of computer-aided design (CAD), simulation, graphics and animation. In this work, the authors aim at utilising some of the computer hardware and software tools available in the market and tailor them to the needs of the construction managers. In simulation, computer models are used to imitate the behaviour of the real situation as a function of time. As the simulation advances with time, pertinent statistics are gathered about the simulation system in very much the same way it is carried out in real life. 0928-4869/94/$07.00
0 1994 Elsevier Science B.V. All rights reserved SSDI 0928-4869(94)0001 l-5
78
Z. B. Harm, G. Singh J Simulation Practice and Theory 2 (I 994) 77-90
Computer visualization is a new and emerging area that is having an impact on how computers are used in research. It is concerned with techniques that allow engineers to extract knowledge from the results of simulations and computations. Advances in computer simulations have enabled complex systems to be modelled in great details. This, however, requires the handling of large amount of data. The problem then is how to convey this numerical information to the construction managers and the different parties in construction effectively. Computer generated images are the means used in computer visualization to achieve this communication. It is thought that the portability and low-cost of the microcomputer combined with its increased power, will definitely help to promote further the visualization concept amongst the construction personnel.
2. Background and motivation At present, computer visualization is mainly being applied in the fields of fluid flow, quantum electronics, space research, manufacturing, presentation of three dimensional statistical data, etc. [6]. On the whole, most applications are used only in research laboratories and run on large mainframe computers. Microcomputerbased animations are usually limited to applications that do not require extensive shading or colouring, and where a small part of the screen graphics needs updating to reflect the effect of motion. In these applications, display resolution is not high, the colour range is limited and the forms are simple. With the advent of the powerful 32-bit microcomputers with large memory capacities and high resolution monitors, most of these limitations are easily overcome. Now, for under &4000, the new breed of processors and high resolution screens offer the opportunity to develop interactive graphics systems tuned specifically for construction design. This also opens up the way for the applications of visualisation in construction planning. The current trend in the use of computer-aided design (CAD) which appears to be gathering momentum, is towards greater integration of computer applications [ 71. The development of CAD is an important element within this trend. The concept of integration treats the design process as an early phase of a much more extensive process. This extends from the initial requirement, through conceptual and detailed design, construction, commissioning, acceptance and payments, operation and maintenance, possibly to refurbishment activity, and onward until ultimate dismantlement. It is foreseeable that CAD tools and the visualisation approach will be used more widely in all these stages in the future. The software tool developed in this work is aimed at illustrating the potentials of the CAD tools and the visualisation approach as decision support tools in construction projects management. One of the main research works in this area is taking place at Virginia Tech. [ 51. The work focused on a model which integrates Computer-Aided Design technology with Expert Systems technology. It simulates the construction process on a graphics display of a super workstation. The sequence of activity execution is generated by a knowledge-based expert system. This is accomplished by extracting the spatial relationships among various components of the designed facility from the geometric and
Z. B. Harun, G. Singh / Simulation Practice and Theory 2 (1994) 77-90
79
topological data stored in a 3-D computer model. The extracted data and knowledge rules, stored in the knowledge-base of an expert system, are used to dynamically generate the execution sequence. The generated sequence is then used to visually simulate the construction process using WALKTHRU. WALKTHRU is a 3-D visual simulation system which offers object-oriented computer modelling and manipulation capabilities developed by Bechtel [S]. It is a real-time, 3-D animation and visualization system which allows the user to simulate a walk-through of a facility which exists as a 3-D computer model. The system runs on a Silicon Graphics IRIS workstations and currently is being implemented to run on SUN workstations with Raster Technology. It can interface with many CAD systems using its own modelling interface programs. Morad and Beliveau [ 51 also proposed a knowledge-based planning system where computer-aided design (CAD) technology was to be used to generate and simulate construction plan. The proposed system, named as KNOW-PLAN, was an attempt at approaching the planning problem via the integration of CAD and AI. The overall system was divided into six stages: (1) Generation of a 3-D computer model. (2) Data-base and knowledge-base creation and manipulation. (3) Dynamic sequencing process. (4) Interactive sequence modification. (5) Conventional scheduling and reporting. (6) Visual simulation of the construction process. The WALKTHRU system was to be used in stage 1 of the overall system. It was foreseen that the system will be able to generate construction plans using the knowledge-based system. The generated sequence was to be based on the spatial relationships among various components of the designed facility, which were to be extracted directly from the 3-D model of the facility. The overall system was proposed to run on a workstation minicomputer configuration under the UNIX operating system. In the field of visualization of construction processes for planning and monitoring of projects also, Retik [S] produced some useful proposals and demonstrated them via some visual computer screen print-outs of certain construction work in progress. His approach was based on visualization of situations and/or solutions generated by a computerised system during the planning process. This paper concentrates on enabling designer or clients to observe construction features from different angles or even walk through its various parts (similar to WALKTHRU approach) i.e. ability to show picture of the work progress, indicating deviation from the planned schedule - valuable for those dealing with co-ordination of and resource allocation for several projects concurrently. This approach is based on the visualization of basic activities of construction processes where each activity has, as its attributes, the planned start, the duration, their graphical and geometrical representation and their location in the project space. Each activity is composed from a parametric “library” of basic elements such as walls, columns, windows, etc., created for specific purposes and as a result could be adapted to the desired dimensions and position. The paper does not give clarification on the hardware and software used for the development of the
80
2. B. Harun, G. Singh J Simulation Practice and Theory 2 (1994) 77-90
visualization system. This gives the impression that the development of the system is still at the conceptual stage. For example, Retik states that the development was based on logic (e.g. PROLOG) or object-oriented languages. At this stage, he should be more decisive as to which approach he chose to adopt (i.e. if he had done some initial work in the development of the prototype system). Also, even though the 3-D graphics displayed in his paper looked impressive, those graphics could have been produced “statically” with the use of a standard CAD software. The main question is whether the CAD images were dynamically linked to the project planning package and thus managed to do what he claimed they could do. The difficult part is to link them to the project planning part of the software in a dynamic manner. In the authors’ experience, in making the linking possible, the choice of the programming languages or environment for developing the visualization package and the project planning package played an important role. Certain facilities such as multi-tasking and dynamic data exchange were undoubtedly vital in determining the success of integrating the two packages dynamically.
3. Module features The visualization software discussed in this paper formed an integrated part of an overall simulation software developed by the authors. The overall simulation software is as shown in Fig. 1. The simulation models were based on earlier work at the Civil
2 The Interface Module
I
w 4 The Simulation
b Module
3 The Database Module
t
t
Fig. 1. The overall
simulation
system software
Z. B. Harm, G. Singh / Simulation Practice and Theory 2 (1994) 77-90 Table 1 Software
used in development
of visualization
81
system
Software
Roles
Drafix CAD Visual Basic Q + E Database/VB MS Project
Construction of building blocks Visualization screen Storage for building blocks and data Project planning functions
Engineering Dept., University of Leeds [ 1,2]. While earlier papers [3,4] described certain modules in the system, the overall software will be the subject of another paper. This software, in turn forms part of an integrated project management package which, amongst others, integrates the cost, time and control functions [9]. This section describes the computer software system developed by the authors. It runs under the Windows environment on a PC. Table 1 lists the different software packages used and their specific roles. The DrafixCAD package was used to construct different shapes of polygons which formed the building blocks. These shapes were then stored under a library to ease browsing and retrieval by the user. The user is also allowed to construct their own shapes of polygon and store them in the library, thereby, expanding the size of the library. At the time when this paper was written, the library contained approximately 300 different shapes and colours of polygon. Fig. 2 shows the flowchart for the overall layout of the visualisation module. It shows the running of the program from the start. The user is given the choice of opening a new project or an old one. When the user chooses to open a new project, the library of building blocks will be opened for designing the layout of the project. For old projects, the design data will have been stored in the database in earlier work and thus this data will be retrieved and used to run the visualisation program. Fig. 3 shows the internal structure of the visualisation program. In running the program, the user is given the choice of step-by-step run, auto-slow and auto-fast run. These choices are given to enable the user to observe the progress of the construction process in the mode that suits him/her. Through the observation, the user would have discovered some discrepancies in the project plan. To alter the plan, the user may choose to change the schedule and again observe the construction process. This process can be repeated until the user is satisfied. Fig. 4 shows the flowchart of the procedures involved in the design of the visual layout. The procedures were carried out under Visual Basic environment’s design time. Picture boxes are filled with pictures from the library of building blocks and then arranged in the appropriate layout. The user will need to have some idea as to how the layout should look like to be able to produce a reasonably good layout. In most situations where the design plans are already available, the screen design procedure will be easy and straight forward as visual copies may be made between the two layout plans. The followings are highlights of some of the important features in the visualization software:
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Z. B. Harun. G. Singh / Simulation
Practice and Theory 2 (1994) 77-90
5 Open
new project
file
Open
6 __,
Input/update names,
activities’
durations
and
_+
specific
project
V 0 Start visualisation
file
program,
sequence
Display
4 9 vlsualisation screen
Design
construction
layouts
plan 8 elevation
Fig. 2. Overall
layout
of the visualisation
-
I
module.
(1) The software was developed to run on the 486 microcomputer at 66 MHz with 8 MBytes RAM 200 MByte hard disk. Under the MS Windows environment which provided multi-tasking and dynamic data exchange facilities, the different software used to develop the final package were integrated and can be run simultaneously. Due to this dynamic linking, the updating of data in one part of the software is automatically reflected in the other linked parts. In practice, when the users have observed the visualisation screen and decided to introduce changes in the schedule of activities, this action will automatically cause changes in the visual display and database. (2) This software includes a visualization module which enables the user to observe the overall construction work progress from the start to completion on the computer
Z.B. Harun. G. Singh / Simulation Practice and Theory 2 (1994) 77-90
83
1
6 Make picture boxes visible one by one
Fig. 3. Internal
structure
of the visualisation
program
screen in a visual form. Once the visualisation program is activated, the individual permanent works which are represented by graphic polygons of different shapes and colours, appears on the screen one by one, thereby imitating the visual view of the work progress in compressed time. The visualisation module was developed using the Visual Basic programming language and the Microsoft Project planning package. This module was integrated with the main software (already developed) which
84
Z.B. Harun, G. Singh / Simulation Practice and Theory 2 (1994) 77-90
1 start
1) 2 Display
menu
buildmg
of
blocks
1 3 Activate
database
bullding
Display
of
blocks
Ibst of selected
buildmg
blocks
I Display
design
screen
No
Arrange
bulldmg
appropriate layout
blocks
into
construction on
Screen
Fig. 4. The design procedures
of visual layout.
simulates materials handling systems. By observing the visual progress of the construction work on the computer screen, the user is able to pin-point any discrepancies in the construction plan well before the problems occur. (3) The database facility enables the user to store and retrieve building information easily. The database contains information on construction work, the building blocks (different polygon shapes) and the library of symbols. The database of projects stores
Z. B. Harm, G. Singh / Simulation Practice and Theory 2 (1994) 77-90
85
the information relevant to each project such as the activities’ names and their sequences, the building blocks representing each activities and the activities’ durations. This database can be expanded further as the needs of the user grow with time. This facility reduces the tedium in handling the large amount of input and output data for the overall module.
4. Module demonstration Fig. 5 shows the visual screen of this module. It shows a sample project of a small residential building. The individual permanent works such as the foundation, ground beam, columns and roof beams are all represented by polygons of different shapes and colours. The door and window shapes are taken from the library of symbols available in the Drafix CAD package. Unusual shapes such as for the drains and the fencing are drawn by the authors. These shapes, once drawn and used, are stored in the database for possible use again in future projects. Fig. 6 shows the starting menu of the visualization module. This menu enables the user to choose between opening an old project or a new one. For old projects, the user copies the data from the database into the visualization module. This is done by retrieving the data from inside the database of projects. For new projects, the
A Small Residential Building:(Elevation/S~tio~} C&struction ProcesG Nos. Name of A&vii
.,&
i t Fence
(back)
-
Duration
’ ;3
Construction Period
; units :; 72
,__.
Fig. 5. The visual screen of the module.
units
86
Z.B. Harun, G. Singh /Simulation
Practice and Theory 2 (1994) 77-90
Database of Building Ellocks:
Fig. 6. Starting
menu of the visualization
module.
user first of all lists the construction activities in the project and their sequences of construction. S/he then works out the geometrical shapes to represent each activities. Once satisfied, s/he may retrieve each shape from the library of building blocks and transfer it into the project database. Fig. 7 shows the list of retrieved names of activities for a project listed according to the sequence of construction. The user then proceeds to the visual screen. When the layout design has been completed, the user starts the visualisation by starting the program. The user is allowed three modes in running the visualisation, namely, “steps”, “auto/slow” and “auto/fast”. Fig. 8 shows the screen when the visualisation is running showing the elevation view. The stage of the construction was completed at the cladding activity as shown in the “Name of activity” box. The duration of the cladding activity was 5 days and the total construction duration was 41 days. Once the user has run the visualisation, s/he may like to change the sequence of construction activities. To change the visual sequence, the user ends the visualisation run to return to the design mode. Then s/he changes the control names for the picture boxes concerned to the appropriate sequences. To change the listed sequence, the user returns to the starting menu and opens the project database. The sequence changes are made by renumbering the activities’ numbers to the appropriate ones. The listing of the activities’ names will be updated automatically.
Z. B. Harun, G. Singh / Simulation Practice and Theory 2 (1994) 77-90
Fig. 7. List of retrieved
names of activities
87
for a project.
The activity list form (Fig. 7) is programmed to be linked to the project planning software (MS Project). By clicking the “ViewChart” button, the project software is opened. The user can view the project in either the bar-chart mode or the network mode. Figs. 8 and 9 show the project views in the bar-chart and network modes respectively.
5. Discussion Up till now, microcomputer-based animations were usually limited to applications that do not require extensive shading or colouring, and where a small part of the screen graphics needs updating to reflect the effect of motion. This type of animation is classified as real-time animation in the sense that moving graphics are displayed as soon as they are generated. In these applications, display resolution is not high, the colour range is limited and the forms are simple. With the advent of the powerful 32-bit microcomputers with large memory capacities and high resolution monitors, most of these limitations are easily overcome. In this software development work, the authors had chosen the PC environment. To further enhance the speed of running the program, the building blocks were all saved under the Windows Metafile format (WMF). Under this format, the memory
88
Z. B. Harun, G. Singh / Simulation
Pd -._. ID
Name
Practice and Theory 2 (1994) 77-90
._--.
111 _.
Excavason work
56.
Grou
5d, 56
74 ams
Goiumns
s/3/93 8:oo iE%X#38:00
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9d
Cladding
56
914193 a:#0
Roohng
7d
15/4/93 8:oo
Lxalns -
36
22/4#3
8:W
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8:W
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2fs%Ki 8:oo 2914193 &c@
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Roads (access) Landscape
Fence - back Fwce _hmt
,4f3 2,f3 2
2&2/938:00 D
Columra RooRx?ams
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--_--____
Duratmon Scheduled Start R,2en ,f3
3f5m3 8:M) 36:
71993 8:M)
34
12&X93 8:oD
3d
1715i33 8:#
Fig. 8. The project
view in bar-chart
mode.
consumed is smaller (cf. Bitmap format). The smaller memory consumption means that the time required to access the graphical data is smaller and thus higher program running speed. This work aims at illustrating the concept of integrating the design and planning tasks in construction. The software still needs to be fine tuned to achieve other more detailed tasks such as budget planning. This also includes validating the software against real life projects. Further enhancement of the software is also possible such as 3-D visualisation and more dynamic linking of data. At the time when this paper was written, these enhancements could not be achieved due to software limitations. In this work, the authors consider visualisation to be a viable and desirable decision and monitoring/control aid. In the computer visualisation of the construction work, the time scale is compressed. As such, construction work that would take years to complete can be visualised from start to completion in minutes. Whilst there is great deal of room for enhancement and improvements, the advantages of the current visualization system include: . The package assists the employer, planner, engineer and site foreman, etc. in getting a better perception of the work logic and progress. . The designer is helped to understand the effects of his/her design on the constructability. This will help in the production of better and more economical designs for the future.
Z.B. Harun, G. Singh / Simulation
Fig. 9. The project
Practice and Theory 2 (1994) 77-90
view in network
89
mode.
In large scale projects, this approach can be extended to monitoring the construction processes and the related activities such as on-site plant and equipment. Locations of construction equipment and temporary facilities may be checked in space and traced in time. Where plant are used, project delays and interferences may be prevented. The construction managers are presented with a powerful communication tool to convey important information to their subordinates and superiors. This tool will also helps in improving the client-consultant-contractor relationship through improved mutual understanding of the project in hand. The package is a valuable tool for computer aided learning of construction projects scheduling and planning.
6. Conclusions This paper highlights the potentials of the visualization system in construction management which presents an opportunity for integrating design, engineering and construction planning processes in a more cost effective way. This, in turn, should spark off new ideas on how to further utilise the visualization concept in achieving
90
2. B. Harun. G. Singh J Simulation Practice and Theory 2 (1994) 77-90
construction project objectives of attaining construction quality within the cost and time parameters. The low-cost solution presented in this paper is thought to be more accessible to a wider spectrum of users in the construction industry. Particularly, this software will be of value to medium to small contractors in the industrially advanced countries and all contractors in the other countries. This package is useful for computer aided learning of scheduling and construction.
References [l]
J.M. Bournazos, Optimization of material handling systems A simulation approach, MSc. Dissertation, Dept. of Civil Engineering, University of Leeds, 1975. [2] Z.B. Harun, Microcomputer simulation models for optimization of materials handling systems in the construction industry, MSc. Dissertation, Leeds University, 1987. [ 31 Z.B. Harun and G. Singh. Visual manipulation of input probability curves in stochastic simulation models of construction materials handling systems, in: J.J. Connors, S. Hernandez, T.K.S. Murthy and H. Power. eds., Visualization and Intelligent Design in Engineering and Architecture (Computational Mechanics and Elsevier Science, Southampton/London, 1993) 5577570. [4] Z. Harun and G. Singh. An intelligent help module for stochastic simulation models of construction materials handling systems, in: B.H.V. Toppings and A.I. Khan, eds., Proceedings Civil-Camp ‘93 Information Technology for Civil and Structural Engineers, Edinburgh (1993) 101-107. [5] A.A. Morad and Y.J. Beliveau, Knowledge-based planning system, J. Construction Engineering and Management (March 1991) 1-12. [6] G.M. Nielson and B. Shrivers, eds. Visualization in Scientific Computing (IEEE Computing Society, Los Alamitos, CA, 1990). [7] S. Port, The Management qfCAD,for Construction (BSP Professional, Oxford, 1989) 220-222. [8] A. Retik, Visualization for decision making in construction planning, in: J.J. Connors, S. Hernandez, T.K.S. Murthy and H. Power., eds., Visualization and Intelligent Design in Engineering and Architecture (Computational Mechanics and Elsevier Science, Southampton/London, 1993) 5877599. [9] K. Shaath and G. Singh, A stochastic cost engineering system (SCENS) applied to estimating and tendering for bill of quantities contracts, in: Proceedings of the 5th International Conference on Computing in Cioil and Building Engineering, New York (1993) 1378-1385.
PRACTICE = THEORY
ELSEVIER
Simulation Practice and Theory 2 (1994) 77-90
Visual simulation of construction microcomputer Z.B. Harun
a, G. Singh
projects on a b*
a Department of Civil Engineering, Universiti Malaya, Kuala Lumpur, Malaysia b Department of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom Received 1 October 1993; revised 1 March 1994
Abstract Under the Microsoft’s Windows environment, Drafix CAD, MS Project, Visual Basic and Q + E Database/VB packages are integrated. This integrated software is able to show the step by step progress of the construction work in compressed time on the computer screen under the Visual Basic environment. The user is allowed to view the project in the bar-chart or network modes under the MS Project environment. This software opens up a new possibility of linking project planning with project design/visualisation in the microcomputer environment. The approach is demonstrated to be feasible and worthy of further development for the benefit of designers and project managers as well as site engineers. Keywords:
Animation;
CAD; Construction;
Logistics;
PC; Projects;
Simulation;
Visualisation
1. Introduction It is generally accepted fact that visually presented information is more easily understood and absorbed than verbal one. Also, visual material instils more confidence in the audience; as the saying goes “Seeing is believing”. This work utilises this in combining low cost visual tools on the microcomputer with overall construction projects scheduling and planning tools. In comparison with the manufacturing industry, the construction industry is slow in utilising the available computer hardware and software. This includes the areas of computer-aided design (CAD), simulation, graphics and animation. In this work, the authors aim at utilising some of the computer hardware and software tools available in the market and tailor them to the needs of the construction managers. In simulation, computer models are used to imitate the behaviour of the real situation as a function of time. As the simulation advances with time, pertinent statistics are gathered about the simulation system in very much the same way it is carried out in real life. 0928-4869/94/$07.00
0 1994 Elsevier Science B.V. All rights reserved SSDI 0928-4869(94)0001 l-5
78
Z. B. Harm, G. Singh J Simulation Practice and Theory 2 (I 994) 77-90
Computer visualization is a new and emerging area that is having an impact on how computers are used in research. It is concerned with techniques that allow engineers to extract knowledge from the results of simulations and computations. Advances in computer simulations have enabled complex systems to be modelled in great details. This, however, requires the handling of large amount of data. The problem then is how to convey this numerical information to the construction managers and the different parties in construction effectively. Computer generated images are the means used in computer visualization to achieve this communication. It is thought that the portability and low-cost of the microcomputer combined with its increased power, will definitely help to promote further the visualization concept amongst the construction personnel.
2. Background and motivation At present, computer visualization is mainly being applied in the fields of fluid flow, quantum electronics, space research, manufacturing, presentation of three dimensional statistical data, etc. [6]. On the whole, most applications are used only in research laboratories and run on large mainframe computers. Microcomputerbased animations are usually limited to applications that do not require extensive shading or colouring, and where a small part of the screen graphics needs updating to reflect the effect of motion. In these applications, display resolution is not high, the colour range is limited and the forms are simple. With the advent of the powerful 32-bit microcomputers with large memory capacities and high resolution monitors, most of these limitations are easily overcome. Now, for under &4000, the new breed of processors and high resolution screens offer the opportunity to develop interactive graphics systems tuned specifically for construction design. This also opens up the way for the applications of visualisation in construction planning. The current trend in the use of computer-aided design (CAD) which appears to be gathering momentum, is towards greater integration of computer applications [ 71. The development of CAD is an important element within this trend. The concept of integration treats the design process as an early phase of a much more extensive process. This extends from the initial requirement, through conceptual and detailed design, construction, commissioning, acceptance and payments, operation and maintenance, possibly to refurbishment activity, and onward until ultimate dismantlement. It is foreseeable that CAD tools and the visualisation approach will be used more widely in all these stages in the future. The software tool developed in this work is aimed at illustrating the potentials of the CAD tools and the visualisation approach as decision support tools in construction projects management. One of the main research works in this area is taking place at Virginia Tech. [ 51. The work focused on a model which integrates Computer-Aided Design technology with Expert Systems technology. It simulates the construction process on a graphics display of a super workstation. The sequence of activity execution is generated by a knowledge-based expert system. This is accomplished by extracting the spatial relationships among various components of the designed facility from the geometric and
Z. B. Harun, G. Singh / Simulation Practice and Theory 2 (1994) 77-90
79
topological data stored in a 3-D computer model. The extracted data and knowledge rules, stored in the knowledge-base of an expert system, are used to dynamically generate the execution sequence. The generated sequence is then used to visually simulate the construction process using WALKTHRU. WALKTHRU is a 3-D visual simulation system which offers object-oriented computer modelling and manipulation capabilities developed by Bechtel [S]. It is a real-time, 3-D animation and visualization system which allows the user to simulate a walk-through of a facility which exists as a 3-D computer model. The system runs on a Silicon Graphics IRIS workstations and currently is being implemented to run on SUN workstations with Raster Technology. It can interface with many CAD systems using its own modelling interface programs. Morad and Beliveau [ 51 also proposed a knowledge-based planning system where computer-aided design (CAD) technology was to be used to generate and simulate construction plan. The proposed system, named as KNOW-PLAN, was an attempt at approaching the planning problem via the integration of CAD and AI. The overall system was divided into six stages: (1) Generation of a 3-D computer model. (2) Data-base and knowledge-base creation and manipulation. (3) Dynamic sequencing process. (4) Interactive sequence modification. (5) Conventional scheduling and reporting. (6) Visual simulation of the construction process. The WALKTHRU system was to be used in stage 1 of the overall system. It was foreseen that the system will be able to generate construction plans using the knowledge-based system. The generated sequence was to be based on the spatial relationships among various components of the designed facility, which were to be extracted directly from the 3-D model of the facility. The overall system was proposed to run on a workstation minicomputer configuration under the UNIX operating system. In the field of visualization of construction processes for planning and monitoring of projects also, Retik [S] produced some useful proposals and demonstrated them via some visual computer screen print-outs of certain construction work in progress. His approach was based on visualization of situations and/or solutions generated by a computerised system during the planning process. This paper concentrates on enabling designer or clients to observe construction features from different angles or even walk through its various parts (similar to WALKTHRU approach) i.e. ability to show picture of the work progress, indicating deviation from the planned schedule - valuable for those dealing with co-ordination of and resource allocation for several projects concurrently. This approach is based on the visualization of basic activities of construction processes where each activity has, as its attributes, the planned start, the duration, their graphical and geometrical representation and their location in the project space. Each activity is composed from a parametric “library” of basic elements such as walls, columns, windows, etc., created for specific purposes and as a result could be adapted to the desired dimensions and position. The paper does not give clarification on the hardware and software used for the development of the
80
2. B. Harun, G. Singh J Simulation Practice and Theory 2 (1994) 77-90
visualization system. This gives the impression that the development of the system is still at the conceptual stage. For example, Retik states that the development was based on logic (e.g. PROLOG) or object-oriented languages. At this stage, he should be more decisive as to which approach he chose to adopt (i.e. if he had done some initial work in the development of the prototype system). Also, even though the 3-D graphics displayed in his paper looked impressive, those graphics could have been produced “statically” with the use of a standard CAD software. The main question is whether the CAD images were dynamically linked to the project planning package and thus managed to do what he claimed they could do. The difficult part is to link them to the project planning part of the software in a dynamic manner. In the authors’ experience, in making the linking possible, the choice of the programming languages or environment for developing the visualization package and the project planning package played an important role. Certain facilities such as multi-tasking and dynamic data exchange were undoubtedly vital in determining the success of integrating the two packages dynamically.
3. Module features The visualization software discussed in this paper formed an integrated part of an overall simulation software developed by the authors. The overall simulation software is as shown in Fig. 1. The simulation models were based on earlier work at the Civil
2 The Interface Module
I
w 4 The Simulation
b Module
3 The Database Module
t
t
Fig. 1. The overall
simulation
system software
Z. B. Harm, G. Singh / Simulation Practice and Theory 2 (1994) 77-90 Table 1 Software
used in development
of visualization
81
system
Software
Roles
Drafix CAD Visual Basic Q + E Database/VB MS Project
Construction of building blocks Visualization screen Storage for building blocks and data Project planning functions
Engineering Dept., University of Leeds [ 1,2]. While earlier papers [3,4] described certain modules in the system, the overall software will be the subject of another paper. This software, in turn forms part of an integrated project management package which, amongst others, integrates the cost, time and control functions [9]. This section describes the computer software system developed by the authors. It runs under the Windows environment on a PC. Table 1 lists the different software packages used and their specific roles. The DrafixCAD package was used to construct different shapes of polygons which formed the building blocks. These shapes were then stored under a library to ease browsing and retrieval by the user. The user is also allowed to construct their own shapes of polygon and store them in the library, thereby, expanding the size of the library. At the time when this paper was written, the library contained approximately 300 different shapes and colours of polygon. Fig. 2 shows the flowchart for the overall layout of the visualisation module. It shows the running of the program from the start. The user is given the choice of opening a new project or an old one. When the user chooses to open a new project, the library of building blocks will be opened for designing the layout of the project. For old projects, the design data will have been stored in the database in earlier work and thus this data will be retrieved and used to run the visualisation program. Fig. 3 shows the internal structure of the visualisation program. In running the program, the user is given the choice of step-by-step run, auto-slow and auto-fast run. These choices are given to enable the user to observe the progress of the construction process in the mode that suits him/her. Through the observation, the user would have discovered some discrepancies in the project plan. To alter the plan, the user may choose to change the schedule and again observe the construction process. This process can be repeated until the user is satisfied. Fig. 4 shows the flowchart of the procedures involved in the design of the visual layout. The procedures were carried out under Visual Basic environment’s design time. Picture boxes are filled with pictures from the library of building blocks and then arranged in the appropriate layout. The user will need to have some idea as to how the layout should look like to be able to produce a reasonably good layout. In most situations where the design plans are already available, the screen design procedure will be easy and straight forward as visual copies may be made between the two layout plans. The followings are highlights of some of the important features in the visualization software:
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5 Open
new project
file
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Design
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Fig. 2. Overall
layout
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-
I
module.
(1) The software was developed to run on the 486 microcomputer at 66 MHz with 8 MBytes RAM 200 MByte hard disk. Under the MS Windows environment which provided multi-tasking and dynamic data exchange facilities, the different software used to develop the final package were integrated and can be run simultaneously. Due to this dynamic linking, the updating of data in one part of the software is automatically reflected in the other linked parts. In practice, when the users have observed the visualisation screen and decided to introduce changes in the schedule of activities, this action will automatically cause changes in the visual display and database. (2) This software includes a visualization module which enables the user to observe the overall construction work progress from the start to completion on the computer
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1
6 Make picture boxes visible one by one
Fig. 3. Internal
structure
of the visualisation
program
screen in a visual form. Once the visualisation program is activated, the individual permanent works which are represented by graphic polygons of different shapes and colours, appears on the screen one by one, thereby imitating the visual view of the work progress in compressed time. The visualisation module was developed using the Visual Basic programming language and the Microsoft Project planning package. This module was integrated with the main software (already developed) which
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1 start
1) 2 Display
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Fig. 4. The design procedures
of visual layout.
simulates materials handling systems. By observing the visual progress of the construction work on the computer screen, the user is able to pin-point any discrepancies in the construction plan well before the problems occur. (3) The database facility enables the user to store and retrieve building information easily. The database contains information on construction work, the building blocks (different polygon shapes) and the library of symbols. The database of projects stores
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the information relevant to each project such as the activities’ names and their sequences, the building blocks representing each activities and the activities’ durations. This database can be expanded further as the needs of the user grow with time. This facility reduces the tedium in handling the large amount of input and output data for the overall module.
4. Module demonstration Fig. 5 shows the visual screen of this module. It shows a sample project of a small residential building. The individual permanent works such as the foundation, ground beam, columns and roof beams are all represented by polygons of different shapes and colours. The door and window shapes are taken from the library of symbols available in the Drafix CAD package. Unusual shapes such as for the drains and the fencing are drawn by the authors. These shapes, once drawn and used, are stored in the database for possible use again in future projects. Fig. 6 shows the starting menu of the visualization module. This menu enables the user to choose between opening an old project or a new one. For old projects, the user copies the data from the database into the visualization module. This is done by retrieving the data from inside the database of projects. For new projects, the
A Small Residential Building:(Elevation/S~tio~} C&struction ProcesG Nos. Name of A&vii
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units
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Practice and Theory 2 (1994) 77-90
Database of Building Ellocks:
Fig. 6. Starting
menu of the visualization
module.
user first of all lists the construction activities in the project and their sequences of construction. S/he then works out the geometrical shapes to represent each activities. Once satisfied, s/he may retrieve each shape from the library of building blocks and transfer it into the project database. Fig. 7 shows the list of retrieved names of activities for a project listed according to the sequence of construction. The user then proceeds to the visual screen. When the layout design has been completed, the user starts the visualisation by starting the program. The user is allowed three modes in running the visualisation, namely, “steps”, “auto/slow” and “auto/fast”. Fig. 8 shows the screen when the visualisation is running showing the elevation view. The stage of the construction was completed at the cladding activity as shown in the “Name of activity” box. The duration of the cladding activity was 5 days and the total construction duration was 41 days. Once the user has run the visualisation, s/he may like to change the sequence of construction activities. To change the visual sequence, the user ends the visualisation run to return to the design mode. Then s/he changes the control names for the picture boxes concerned to the appropriate sequences. To change the listed sequence, the user returns to the starting menu and opens the project database. The sequence changes are made by renumbering the activities’ numbers to the appropriate ones. The listing of the activities’ names will be updated automatically.
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Fig. 7. List of retrieved
names of activities
87
for a project.
The activity list form (Fig. 7) is programmed to be linked to the project planning software (MS Project). By clicking the “ViewChart” button, the project software is opened. The user can view the project in either the bar-chart mode or the network mode. Figs. 8 and 9 show the project views in the bar-chart and network modes respectively.
5. Discussion Up till now, microcomputer-based animations were usually limited to applications that do not require extensive shading or colouring, and where a small part of the screen graphics needs updating to reflect the effect of motion. This type of animation is classified as real-time animation in the sense that moving graphics are displayed as soon as they are generated. In these applications, display resolution is not high, the colour range is limited and the forms are simple. With the advent of the powerful 32-bit microcomputers with large memory capacities and high resolution monitors, most of these limitations are easily overcome. In this software development work, the authors had chosen the PC environment. To further enhance the speed of running the program, the building blocks were all saved under the Windows Metafile format (WMF). Under this format, the memory
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consumed is smaller (cf. Bitmap format). The smaller memory consumption means that the time required to access the graphical data is smaller and thus higher program running speed. This work aims at illustrating the concept of integrating the design and planning tasks in construction. The software still needs to be fine tuned to achieve other more detailed tasks such as budget planning. This also includes validating the software against real life projects. Further enhancement of the software is also possible such as 3-D visualisation and more dynamic linking of data. At the time when this paper was written, these enhancements could not be achieved due to software limitations. In this work, the authors consider visualisation to be a viable and desirable decision and monitoring/control aid. In the computer visualisation of the construction work, the time scale is compressed. As such, construction work that would take years to complete can be visualised from start to completion in minutes. Whilst there is great deal of room for enhancement and improvements, the advantages of the current visualization system include: . The package assists the employer, planner, engineer and site foreman, etc. in getting a better perception of the work logic and progress. . The designer is helped to understand the effects of his/her design on the constructability. This will help in the production of better and more economical designs for the future.
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Fig. 9. The project
Practice and Theory 2 (1994) 77-90
view in network
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mode.
In large scale projects, this approach can be extended to monitoring the construction processes and the related activities such as on-site plant and equipment. Locations of construction equipment and temporary facilities may be checked in space and traced in time. Where plant are used, project delays and interferences may be prevented. The construction managers are presented with a powerful communication tool to convey important information to their subordinates and superiors. This tool will also helps in improving the client-consultant-contractor relationship through improved mutual understanding of the project in hand. The package is a valuable tool for computer aided learning of construction projects scheduling and planning.
6. Conclusions This paper highlights the potentials of the visualization system in construction management which presents an opportunity for integrating design, engineering and construction planning processes in a more cost effective way. This, in turn, should spark off new ideas on how to further utilise the visualization concept in achieving
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construction project objectives of attaining construction quality within the cost and time parameters. The low-cost solution presented in this paper is thought to be more accessible to a wider spectrum of users in the construction industry. Particularly, this software will be of value to medium to small contractors in the industrially advanced countries and all contractors in the other countries. This package is useful for computer aided learning of scheduling and construction.
References [l]
J.M. Bournazos, Optimization of material handling systems A simulation approach, MSc. Dissertation, Dept. of Civil Engineering, University of Leeds, 1975. [2] Z.B. Harun, Microcomputer simulation models for optimization of materials handling systems in the construction industry, MSc. Dissertation, Leeds University, 1987. [ 31 Z.B. Harun and G. Singh. Visual manipulation of input probability curves in stochastic simulation models of construction materials handling systems, in: J.J. Connors, S. Hernandez, T.K.S. Murthy and H. Power. eds., Visualization and Intelligent Design in Engineering and Architecture (Computational Mechanics and Elsevier Science, Southampton/London, 1993) 5577570. [4] Z. Harun and G. Singh. An intelligent help module for stochastic simulation models of construction materials handling systems, in: B.H.V. Toppings and A.I. Khan, eds., Proceedings Civil-Camp ‘93 Information Technology for Civil and Structural Engineers, Edinburgh (1993) 101-107. [5] A.A. Morad and Y.J. Beliveau, Knowledge-based planning system, J. Construction Engineering and Management (March 1991) 1-12. [6] G.M. Nielson and B. Shrivers, eds. Visualization in Scientific Computing (IEEE Computing Society, Los Alamitos, CA, 1990). [7] S. Port, The Management qfCAD,for Construction (BSP Professional, Oxford, 1989) 220-222. [8] A. Retik, Visualization for decision making in construction planning, in: J.J. Connors, S. Hernandez, T.K.S. Murthy and H. Power., eds., Visualization and Intelligent Design in Engineering and Architecture (Computational Mechanics and Elsevier Science, Southampton/London, 1993) 5877599. [9] K. Shaath and G. Singh, A stochastic cost engineering system (SCENS) applied to estimating and tendering for bill of quantities contracts, in: Proceedings of the 5th International Conference on Computing in Cioil and Building Engineering, New York (1993) 1378-1385.