A dynamic 4D simulation system for construction ...

David Heesom and Lamine Mahdjoubi

DMinUCE London 2002

A dynamic 4D simulation system for construction space planning David Heesom, School of Engineering and Built Environment, University of Wolverhampton, UK Lamine Mahdjoubi, School of Engineering and Built Environment, University of Wolverhampton, UK

ABSTRACT The effective analysis of space usage on the construction site is imperative to the successful completion of a project. Generally experienced project planners undertake this analysis, however the number of experienced project planners is decreasing, whilst new computing methods and tools allow this process to be supported. Some of the most difficult activities to plan in a construction project are those that rely on specialist trade contractors, for example mechanical and electrical and groundwork’s. Often, it is the case that these operations present serious logistical problems leading to considerable impact on the project duration and cost. This paper reports on the development of a system that allows specialist trade planners to add plant and temporary workspaces to dynamic plans of the construction site prior to the commencement of work. This information can then be viewed in a 4D virtual reality environment. Keywords: 4D CAD, Virtual Reality, Space Planning

INTRODCUTION 4 dimensional (4D) construction planning provides the ability to represent construction plans graphically (Williams, 1996) by adding the temporal dimension to 3D CAD models, i.e. linking a 3D graphical model to a construction schedule through a third party application (Collier and Fischer, 1996; McKinney et al., 1996). It has also been suggested that project managers and planners who use 4D simulations are likely to allocate resources more effectively than those who do not (Fischer, 2000). The use of 4D Planning assists the planner in avoiding scheduling conflicts whilst analysing constraints and evaluating alternative construction methods (Vaugn, 1996). The planning of effective space usage on the construction site is a complex task and one that is often left to the intuition of the construction planner. Previous research has indicated that poor site logistics accounted for over 20% of all accidents on sites (Nutt et al., 1998). Additionally, poor spatial planning has been attributed to major sources of productivity loss (Akinci, 2000; Kelsey et al., 2001; Riley, 1994; Thabet and Beliveau 1997). Work undertaken by Riley (1998) suggested that workspace should be included into 4D simulations to enhance the value of their analytical potential. He also suggested that 4D simulations could be best utilised if focused on problematic trades, such as electrical, plumbing and curtain wall operations. Further research completed by Akinci (2000), demonstrated that 4D simulations could be used to highlight potential time-space conflicts on the construction site. This work aimed to detect conflicts in four dimensions, categorise the conflict according to taxonomy of time-space conflicts developed and prioritise the multiple types of conflicts between the same pair of conflicting activities. The objective of this paper is to report on the development of a system to allow construction planners from specialist trade industries, such as mechanical and electrical and groundwork, to interactively plan the use of space more effectively. It is noted that this research effort is a part of a substantial collaborative research project, The Virtual Construction Site: A Decision Support System for Construction Planning (The VIRCON project) (North & Winch 2002). This project aims to push forward the art of construction planning and scheduling through visualisation and optimisation of the construction site operations and space availability in particular.

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DMinUCE London 2002

DEVELOPMENT METHODOLOGY In order to develop a methodology for software development, this task focused on groundwork operations and mechanical and electrical service installations. Previous research and interviews with numerous construction planners (Kelsey et al., 2001) demonstrated that these provide the most challenging area of spatial analysis for the construction planner. To obtain a greater comprehension of spatial problems associated with mechanical and electrical installations (M&E), preliminary work was undertaken ABB Consultants who were responsible for the M&E operations on the construction of the Teesside University School of Health building. The research undertaken with ABB demonstrated that supporting plant and temporary works played a considerable role during space analysis of the trade operations. For many mechanical and electrical tasks supporting plant is required, for example scaffold towers and telescopic trucks. Additionally the route paths for these supporting objects are vital and so, these factors are required to be taken into account for both the generation of a comprehensive space analysis and any 4D visualisation. Case studies of projects undertaken by Stent foundations and BCJV developed a greater knowledge of the spatial requirements of groundwork operations. A requirements capture exercise was undertaken to ascertain current working practices for site logistics planning and to determine what a developed tool would require. From this work, it became evident that the main consideration when planning space for groundwork tasks was plant equipment and safety areas. In addition to the execution space required by plant objects, it also became apparent from the study that during work processes paths were a critical factor. This was particularly apparent where the site was of a constrained nature. The studies undertaken reinforced the theory postulated that in order for a complete spatial analysis the space requirements of both plant objects and temporary works must be observed. In order to develop a system that was capable of allowing the construction planner to mark up execution space and route paths and visualise these spaces in relation to the constructed product in a 4D virtual reality environment various objectives were defined: • • • •

The development of a electronic mark up tool to allow the planner to add plant and temporary works objects to 2D plans. The development of a Real Time visualisation system that would provide the user with a 4D simulation of the construction process. The ability of the developed system to operate independently of any proprietary software systems, whilst also being intuitive and easy to use. The provision to incorporate paths into the simulation. Research showed that paths are of vital importance to the construction processes in particular specialist trade operations and are required to be incorporated into the simulation.

The research undertaken into the areas of specialist trade visualisation demonstrated it would be complete without the concurrent visualisation of the rest of the building product. Therefore a methodology was developed that allowed both the simulation of specialist trades in conjunction with the visualisation for the whole building. The main inputs for a 4D visualisation are the initial geometry of the 3D building products and the schedule of activities. Both geometry and temporal data for the visualisation are stored in a central VIRCON database developed by Dawood et al. (2001). The VIRCON database is based on the Microsoft Access relational database platform and is structured based on an approach of linking Product Breakdown Structure (PBS) and Work Breakdown Structure (WBS) using the Unified Classification System for the Construction Industry (UNICLASS).

INTERACTIVE SPACE ASSIGNMENT The Plant and Temporary Works Manager (PlantMan) was developed as an interactive ‘mark-up’ tool to allow the construction planner to assign plant and temporary works objects to 2D plans of the building at weekly intervals. Research undertaken by Kelsey et al. (2001) proposed that the majority of space planning was currently undertaken

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at a weekly interval. This interval was chosen as the optimum-planning period Previous work in the area of site layout planning (Tommelein, 1994), demonstrated that using drag and drop templates of objects representing materials are beneficial in developing a site layout plan. This theory is used and extended further to provide objects that could be positioned onto the plan. A resource library was developed that included all plant and temporary works objects that may be required along with their spatial dimensions, including safe working distances. Currently planners ‘mark up’ plans to show areas that are unable to be used by activities manually however this tool aims to provide a semi automated approach to this mark up whilst extending this process into the digital genre therefore allowing more accurate and robust layouts. From the requirements capture exercise undertaken with ABB, Stent and BCJV it became apparent that construction planners require a tool that is quick and easy to use. Additionally it was important that the development of the software did not rely on high-end commercial packages. For this reason PlantMan was developed as a standalone tool using Visual Basic and utilising DAO 3.6 to access the VIRCON database for geometric and temporal information. Figure 1 shows the process architecture of the PlantMan tool: PlantMan allows the construction planner to select a monitoring date within the construction schedule and will display a 2½D (2D+Time) representation of the building or project. Various colours are used to represent the following products: • Completed building products • Building products under construction • Completed specialist trade products • Specialist trade products under construction Resource Library

Input

VIRCON database

Select date to assign Plant / Temp Works objects

Plant Man Process

Draw weekly layout plan using PlantMan interactive whiteboard

Select resource to add to site plan from resource library

Drag and Drop Plant template onto weekly layout

Figure 1: PlantMan process architecture

Output

Assign path / routes for plant for the week and assign plant templates from resource library to paths

Plant-Space Loaded Weekly Product Geometry

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Once a date is selected and the geometry has been drawn, the planner can select an object from the resource library and place this onto the weekly layout. The facility also exists for the planner to select multiple weeks for the position of the object. So, for example, scaffold can be positioned for multiple weeks. If this is the case, once positioned the space object will appear in any future dates selected by the planner. Within PlantMan, the planner also has the ability to draw route paths and assign plant objects to the path. For example, an excavator may be required to move between the material lay down area and a workface. Once the allocation of plant and temporary workspace has been completed, the information can be visualised in a 4D environment.

4D VISUALISATION DEVELOPMENT The 4D Construction Space Visualisation tool (SpaceVis) is a prototype 4D visualisation software system, developed to allow the user to visualise the status of the project at any stage of the construction process. Additionally, the tool allows an intelligent and interactive 3D and 4D visualisation of space usage throughout the duration of the construction period (Figure 2).

Figure 2: SpaceVis 4D interface SpaceVis utilises the geometric information stored in the VIRCON database, along with the spatial information of plant and temporary works input by the planner via the PlantMan tool, to generate VRML objects ‘on the fly’. All of the geometry generated in VRML is based on a weekly take off of activities and space. The 4D VRML simulator is platform and software independent however in order to view the 3D VRML objects a VRML plug in is required. Plug-ins, such as Cortona VRML Client and Cosmo Player, are free to download from the World Wide Web. The SpaceVis tool has been developed using Visual Basic Programming Language to allow the dynamic generation of VRML code from user input. The process architecture of SpaceVis can be seen in Figure 3. Navigation of a virtual reality environment can be delicate and so the ability to draw a predetermined path in 2D will assist the planner in ensuring that all required detail is seen. If the planner wishes to generate an animated path, whiteboard is presented with a 2D plan of the construction site drawn. The planner can simply click the locations of the points he would like to visit. This information is then transferred to key points on an animated path that can be followed by selecting it from the viewpoint list in the VRML window.

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VIRCON Database

DMinUCE London 2002

Geometry Exported from PlantMan

Input


Generate associated attributes files for VRML space objects

SpaceVis Process

Generate VRML Files for product and space objects

Link VRML objects with attribute files to create intelligent objects

Space Object attribute Files

Select monitoring date

Output

Weekly VRML Files

4D VRML Simulation

Figure 3: SpaceVis process architecture Spaces are displayed as rectangular blocks in the simulation. Additionally the VRML objects make use of position interpolators to generate moving objects depicting plant objects moving along paths input using PlantMan. Due to the nature of VRML, objects can also be made intelligent. This use of intelligent objects is exploited in SpaceVis to enable the planner to interact with the visualisation. The user is able to request information from objects in the visualisation. Dynamic objects can also be used and visualised in VRML. This enables the viewing of objects following paths as generated using the PlantMan Interactive Path Assigner. Once a monitoring date has been selected, the date can be increased or decreased by 1 week by using the ‘video style’ buttons on the control panel. Additionally the double arrow buttons run the simulation automatically by increasing or decreasing the week on a preset time so that the simulation can be viewed automatically on a week-byweek basis.

CONCLUSIONS AND FUTURE WORK Various projects were used during the development of the software prototypes. The Teesside University School of Health Building was the primary data source for development and validation has been undertaken using this project during the development phase. The tools are also being validated on £1.25 million project to construct the Westmorland primary school in Stockport, UK. This project is nearing completion and so a retrospective validation

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can be undertaken in order to determine if the use of the tools would have affected how spatial planning of the specialist trades was done and also if any spatial conflicts that did occur during the construction phase could have been identified prior to their occurrence. Additionally the tools will be validated further on a dedicated groundwork project to assess their viability for these types of operation. Various limitations have been identified of the prototype systems and these will be addressed in future developments including: • The development of PlantMan to become 3D. At present the allocation of plant and temporary works objects is limited to 2½ D (i.e. 2D + Time). Future developments will involve the ability to add objects in a 3D VR interface. • Currently the geometry is relatively static. For example, although completed work and work in progress is presented to the planner differently, an entire group of products is displayed for the entire duration of the task. Future developments will include the use of construction strategies to enable the planner to assign a start point and strategy to the task and so dynamically generate geometry throughout the task duration. • At present the path assignment tool is limited to 2 control points. Further enhancement of the dynamic path tool would allow the inclusion of a greater number of control points. Additionally, in order to make the 4D simulation more realistic, the frequency of objects travelling along the path should be adjustable. Currently, plant objects travel along the path at constant rate continuously, however in reality this will vary. For example, a delivery may only happen once a week that would allow that space to be available for temporary works for the remainder of the day

REFERENCES Akinci, B., Fischer, M., Levitt, R. and Carlson, R. (2000) Formalisation and Automation of Time-Space Conflict analysis. Working Paper #59. CIFE, Stanford. Collier, E. and Fischer, M. (1996) Visual Based Scheduling: 4D modelling on the San Mateo County Health Centre. Proc. Of the Third Congress in Computing in Civil Engineering, ASCE, Anaheim, CA, 800-805. Dawood, N., Sriprasert, E. & Mallasi, Z. 2001a. Data capture and database development. Task 2: VIRCON Technical Report. University of Teesside. Fischer, M. (2000) Benefits of 4D models for Facility Owners and AEC Service Providers. Construction Congress VI, ASCE, Orlando, Florida, February 2000. Eds Walsh, K.D. 990-995 Kelsey, J., Winch, G. and Penn, A. (2001) Understanding the Project Planning Process: Requirements Capture for the Virtual Construction Site. Bartlett Research, Paper No. 15. University College London, UK. McKinney, K., Kim, J., Fischer, M. and Howard, C. (1996) Interactive 4D CAD. Proc. Of the Third Congress in Computing in Civil Engineering, ASCE, Anaheim, CA, 383-389. North, S. & Winch, G.M. 2002. VIRCON: a proposal for critical space analysis in construction planning. ECPPM, Slovenia, 9-11 September 2002. Rotterdam: Balkema. Nutt, B, McLennan, P. and Walters, R (1998) Refurbishing occupied buildings: management of risk under the CDM Regulations. Thomas Telford: London Riley, D. (1994). Modeling the Space Behavior of Construction Activities. Ph.D. Thesis, Department of Architectural Engineering, The Pennsylvania State University. Riley, D. (2000) The Role of Four-Dimensional (4D) Modeling in Trade Sequencing and Production Planning. Construction Congress VI, ASCE, Orlando, Florida, February 2000. Eds Walsh, K.D. 1029-1034 Riley, D., (1998). 4D Modeling Specifications for Construction Work Spaces. Proceedings 5th ASCE Congress on Computing in Civil Engineering, 1998, Boston, MA. Thabet, W. Y. and Beliveau, Y. J. (1997) SCaRC: Space-Constrained Resource-Constrained Scheduling System. ASCE, Journal of computing in Civil Engineering, 11 (1) 48 – 59 Tommelein, I.D. (1994). "MoveCapPlan: An Integrated System for Planning and Controlling Construction Material Laydown and Handling." Proc. 1st Computing Congress, ASCE, New York, NY, 1172-1179. Vaugn, F. (1996) 3D and 4D CAD Modeling on Commercial Design-Build Projects. Computing in Civil Engineering Congress 3. Anaheim, California. June 1996. Eds Vanegas, J and Chinowsky, P. 390-396 Williams, M. (1996) Graphical Simulation for Project Planning: 4D-Planner. 3rd Congress on computing in civil Engineering, ASCE. 404-409

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