4D WORKSPACE CONFLICT DETECTION AND ANALYSIS SYSTEM

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1 10th International Conference on Construction Applications of Virtual Reality, D WORKSPACE CONFLICT DETECTION AND ANALYSIS SYSTEM I-Chen Wu, Assistant Professor Department of Civil Engineering, National Kaohsiung University of Applied Sciences Yen-Chang Chiu, Research Assistant Department of Civil Engineering, National Kaohsiung University of Applied Sciences ABSTRACT: Construction activities require a set of adequate workspaces to be executed in a safe and productive manner. This research classifies these required workspaces of activity into five categories: building component spaces, site layout spaces, people working spaces, equipment spaces and material spaces. All of these spaces change and move in three dimensions and across time throughout the construction process. Different activities may occasionally interfere with each another whilst working in the same space, causing space conflicts. In order to avoid the problem of space conflicts during the construction stage, this research develops a 4D workspace conflict detection and analysis system. Our system is implemented on top of Bentley MicroStation which supports both visualization of a 3D building model with capabilities for 3D object manipulation and information querying, and provides an API (Application Programming Interface) for functionality extensions. In this system, four types of space conflict are implemented: design conflict, safety conflict, damage conflict and congestion. Moreover, this system provides a visual environment, such as 3D visualization and 4D simulations, to present work space utilization of the ongoing project and the conflict status of activities with different colors. In this paper, the design and implementation of the 4D workspace conflict detection and analysis system is discussed and sample construction example is used to demonstrate the applicability of the system. KEYWORDS: 4D, Conflict Detection, Conflict Analysis, Workspace, Construction Management 1. INTRODUCTION Space is regarded as a limited resource on construction sites. This becomes apparent when two or more trades are working in the same construction space, potentially interfering with each another, or when the workspace of on-site personnel conflict with material stacking space. These kinds of activity space conflicts occur frequently, severely affecting the process and efficiency of construction and resulting in productivity loss. Construction productivity is thus influenced by a variety of factors. Many researchers have studied the factors that cause loss of productivity in construction sites. Kaming et al. (1998) indicated that space conflicts have been identified as a one of the major causes of productivity loss in construction. Sanders et al. (1989) reported efficiency losses of up to 65% due to congested workspaces and losses up to 58% due to restricted access. Space conflicts can occur in many parts of the construction site and in various stages throughout the construction process. Inadequate workspace and interference during travel can result in access blockage, congestion, safety hazards, and heighten the risk of damaging the end product (Oglesby et al. 1989; Thabet 1992; Tommelein et al. 1992, 1993; Riley and Sanvido 1995; Akinci et al. 1998). Various approaches to ameliorate space conflict have been presented to address the above-mentioned issues. The approach taken in Guo (2002) focused on space availability due to time and scheduling, applying two typical tools, AutoCAD for space planning and MS Project for scheduling, to solve space conflicts. In the past decade, 4D simulation (or 4D CAD) technology, which bind 3D models with their corresponding construction schedules in their simplest form, has made rapid development in providing engineers with an effective tool to manage the coordination complexity of the site, especially in managing conflicts before actual construction commences. The rapid emergence of 4D simulation technology is not only driven by the rapid advancement of information technology, but also by increasing recognition from the construction industry of the benefits of using the 4D CAD applications to increase productivity, improve project coordination, and optimize on-site resources. 4D visualization has emerged as an interesting 4D space planning and visualization tool. 4D space planning specification and construction work development have been investigated by Riley (1998). Akinci et al. (2002a, 2002b, 2002c) also executed similar research which reduces non-value-adding activities due to time-space conflicts. A time-space conflict analysis based on a 4D production model was then proposed. Mallasi s research developed an innovative computer-based tool dubbed PECASO (Patterns Execution and Critical Analysis of Site-space Organization). There is potential for this system to assist site managers in the assignment and identification of workspace conflicts (Mallasi 2004; Dawood and Mallasi 2006). Though much 1

2 Nov. 4-5, 2010 of the research has targeted the space scheduling problem, much less literature is concerned with workspaces for dynamic working objects on construction sites, such as labor and equipment. This is further complicated by the variable requirements of different activities and the change in the location and size of the workspace over time. This study considered the space availability of construction sites in relation to scheduling, productivity loss due to path interference, and space constraints. This research has developed a conflict detection and analysis module based on a 4D CAD system to solve space conflict issues for various working objects in a construction site. Section 2 seeks to define workspace and analyzes the types of workspace conflicts. Section 3 discusses the design and implementation of the conflict detection and analysis module. Section 4 demonstrates the applicability of the 4D workspace Conflict Detection and Analysis System with a construction example. Finally, Section 5 draws our conclusions from the study. 2. DEFINITION OF WORKSPACE CONFLICT A concept diagram of this research is shown below in Fig. 1. The most important impact factors for this research are the requisite workspace for activities during construction, the method of workspace aggregation and the various types of workspace conflict. These will be discussed as follows. Building Site Labor Equipment Material Work Space Conflict Detection and Analysis Design Conflict Safety Hazard Damage Conflict Congestion 2.1 Workspace Fig. 1: A concept diagram of this research. Space is a resource that may cause crucial problems during construction. The construction workspace is a combination of resources, including building component spaces, site layout spaces, human workspaces, equipment spaces and material spaces. Building component: Building component means a specific design or structural element. Each building component, such as a column, beam or wall, is assigned a workspace. The space assigned is the physical space taken up by the building component, as well as providing a buffer required to keep a safe distance around them. Site layout: Construction engineers have to properly allocate construction spaces, such as material storage, the construction site, construction roads and the site office, to minimize the cost of labor and material travel such that the operation is accomplished quickly and efficiently, whilst ensuring the safety of both labor and equipment. Labor: Labor crews need a set of workspaces for constructing building components safely and productively. That is why construction sites need to provide enough space for working and safety, in order to reduce productivity loss and minimize accidents. Equipment: Constructions site need to provide enough operation room for equipment to maneuver safely. 2

3 10th International Conference on Construction Applications of Virtual Reality, 2010 In this manner, the workspace assignment for equipment must consider operation clearance and hazards. Examples of common equipment are cranes, pumps, temporary facilities, and so on. Material: Construction sites need to provide adequate room to store materials properly and allow safe access to them. This kind of workspace assignment must consider protected areas for materials to ensure that they will not be destroyed. Workspace as defined by this research is shown in formula 1. Each object in the model (building component, site layout, labor, equipment and material) has its own space, as well as space needed for operation and safety. This research will calculate how much workspace each object needs and assigns it to them for workspace conflict detection and analysis. Workspace = Space object + Space operation + Space safety... (1) 2.2 Workspace aggregation Construction activities need a set of work spaces to be executed in a safe and productive manner. An example of this would be the pouring of concrete into pad foundation which requires a concrete mixer and a concrete vibrator to accomplish the task. Sufficient workspace needs to be provided for these two pieces of equipment to be able to maneuver safely. Therefore, we must consider workspace aggregation to calculate numerous workspaces at the same time to accurately detect and analyze workspace conflict. In this research, workspaces are created using Constructive Solid Geometry (CSG), a technique used in solid modeling. CSG allows a user to create a complex surface or object by using Boolean operators. The simplest cuboids are used in this research to represent workspaces. We classify workspace aggregation into two ways, with the first being the direct combination of workspaces. For example, since labor objects and equipment objects need independent spaces to operate and for a safety buffer, we can therefore directly combine their workspace cuboids into compound objects using operations such as the merger as shown in Fig. 2. Another aggregation is the combination of working objects. For example, building components and material objects require no space between each other so we can merge two of these objects when they have been installed or assembled, with the workspace for the combined object then recalculated and new workspace cuboids created as shown in Fig. 3. Fig. 2: Direct combination of workspace cuboids. 2.3 Conflict types Fig. 3: Combination of working objects. Project managers need to understand the different types of workspace conflict to develop customized solutions for managing them. According to the literature review, we introduced four major types of conflicts into our system as follows Design conflict Current construction projects are more complex and have more participants involved. When different participants design their own separate parts of the building, design conflicts may occur. We can say that a design conflict occurs 3

4 Path Work Space Status Origin Hight Width Lenght ID Name Path Material Equipment Labor Site Layout Building Component Nov. 4-5, 2010 when a building component conflicts with another. Lack of space and pipeline overlap, for example, may arise from conflict between inappropriate electrical equipment design and HVAC pipe design. The causes of these conflicts are not construction related, but rather, design related Safety Hazard The leading safety hazards on construction sites include being struck by falling objects, motor vehicle crashes, excavation accidents and electrical hazards. A safety hazard conflict occurs when a hazard space generated by an activity conflicts with a labor crew space required by another activity. People are not allowed to pass or stand underneath any loading or digging equipment. Labor crews are to remain at a safe distance from all equipment while it is in operation. When a hazard space conflicts with a labor crew space, it creates a safety hazard situation for the labor crew Damage conflict In order to complete a particular activity, damage to the object or component that is completed in the previous activity may be sustained. A damage conflict occurs when a labor crew space, equipment space, or hazard space required by an activity conflicts with the protected space required by another activity. An example of this is if a worker wants to set up equipment in the correct position and the exit is too narrow or small, they must then remove the door for handling equipment Congestion A congestion conflict occurs when a labor crew and a piece of equipment or material required by an activity needs the same space at same time causing a lack of space or space overlap. Examples of this are when storage space is too small caused by material stacking and overlap, where too many workers are working on the same building component causing congestion or when a large number of construction vehicles are entering or leaving the construction site at the same time causing congestion. 3. CONFLICTS DETECTION AND ANALYSIS MECHANISMS The implementation of our 4D workspace detection and analysis system was carried out in Microsoft s VB.NET environment. During the simulation, the 3D objects in the construction site model are highlighted in different colors depending on their conflict types. 3.1 Workspace Data Model A data model is an abstract model that describes how data is represented and accessed. This research proposed a workspace data model for data definition and storage. This data model includes six main classes, each with their own sub-classes and attributes for detecting and analyzing workspace conflicts as shown in Fig. 4. WorkSpace Data Model Labor Origin X Y Z Work Space ΔL ΔW ΔH (a) WorkSpace Data Model (b) Detail of Data Model for Labor Fig. 4: Workspace data model. 4

5 10th International Conference on Construction Applications of Virtual Reality, Conflict Detection and Analysis Module This research divided working objects into two categories according to their status: static working objects and dynamic working objects. Static working objects include building components, gatherings of people, parked equipment and materials stacks. Dynamic working objects include working people and equipment in operation or transportation. The simulation and visualization of the different working objects is discussed in the following sections Color Schema We defined four colors to visualize the workspace conflicts in 3D environment. Table 1 shows the color scheme implemented with examples of the kind of working objects that will raise the specific conflict. Table 1: Color schema for workspace conflicts. Color Conflict Type Static vs. Static Dynamic vs. Static Dynamic vs. Dynamic Purple Design Conflict Design Interference None None Red Safety Hazard None None Equipment vs. Labor Yellow Damage Conflict None Equipment vs. Building None Green Congestion Material vs. Material Labor vs. Material Equipment vs. Equipment D Visualization This research provides tools for defining the relationships between the objects in the 3D model and time schedule. The system will detect and analyze workspace conflicts between various working objects during 4D visualization. Static working object vs. Static working object Design or congestion conflicts may occur between two static working objects as shown in Fig. 5. For example, design interference between subcontracter and material. Design Conflict Congestion Fig. 5: Conflict visualization between two static working objects. Static working object vs. Dynamic working object Damage conflict or congestion conflict may arise from interaction between a static working object and a dynamic working object. Fig. 6 shows a simple case of equipment being driven to the building component. Assuming construction sites are unable to provide enough path space, damage conflict will occur. 5

6 Nov. 4-5, 2010 Building Component Equipment (1) (2) (3) Damage Conflict Fig. 6: Conflict visualization between a static working object and a dynamic working object. Dynamic working object vs. Dynamic working object (4) (5) (6) Construction sites need to provide enough space for all laborers and equipment as well as for material transportation. For example, where many trucks want to move from the entrance to each working area at same time, congestion conflicts will occur. Fig. 7 is a schematic simulation of labor and equipment. As they move along their own path, a safety hazard conflict occurs. Equipment Labor (1) (2) (3) Safety Hazard Conflict (4) (5) (6) Fig. 7: Conflict visualization between two dynamic working objects. 4. DEMONSTRATION A simple construction site was used as an example to test and demonstrate the functionality of our 4D workspace conflict detection and analysis system, as shown in Fig. 8. Users can create 3D models of working objects (building component, site layout, labor, equipment and material) within the system, which will then calculate and assign the required workspaces for these objects. In this case, the system will only analyze conflicts that deal with labor and equipment for calculatiion efficiently. As labor and equipment moves along a specified path the system will automatically detect and analyze workspace conflicts. Fig. 9 shows the 4D visualization workspace conflicts detection and analysis. In our system, users can observe the whole process simulation. Dynamic working objects, labor and equipment are represented by orange boxes, while the location and size of safety hazard conflicts are depicted by red boxes. 6

7 10th International Conference on Construction Applications of Virtual Reality, 2010 Building Component Site Layout Material Path Labor Equipment Fig. 8: A simple construction site example. (a) (b) (c) (d) Fig. 9: 4D visualization of conflict detection and analysis. 5. CONCLUSIONS Large numbers of building components, workers, equipment as well as materials share limited space during construction. Since space constraints may affect the moving path of resources and productivity, it is essential to detect and analyze workspace conflicts in advance, such that the available space can be used more efficiently. For this reason, this research develops a 4D workspace conflict detection and analysis system for solving space issues in construction sites. In this paper, the 3D CAD system, Bentley MicroStation, was integrated with schedule information for the dynamic identification of space conflicts and 4D visualization. The system can simultaneously detect and analyze workspace conflicts with various working objects, as well as visually representing the location, size, scope and type of workspace conflicts. This will assist project managers in quickly grasping the status of an ongoing project, in order to make decisions. In addition, a simple construction project example was used in this research to demonstrate the functionality and applicability of the 4D workspace 7

8 Nov. 4-5, 2010 conflict detection and analysis system. The workspace conflict that this research focuses on is a common issue in space management. In future, a numerical model and optimization theory will be introduced into our system for space and path planning optimization. 6. ACKNOWLEDGMENTS The authors would like to thank the R.O.C. National Science Council for their financial support under Grant No. NSC E REFERENCES Akinci, B., Fischer, M., and Kunz, J. (2002a). Automated Generation of Work Spaces Required by Construction Activities, Journal of Construction Engineering and Management, 128(4), pp Akinci, B., Fischer, M., Kunz, J. and Levitt, R. (2002b), Representing Work Spaces Generically in Construction Method Models, Journal of Construction Engineering and Management, ASCE, 128(4), pp Akinci, B., Fischer, M., Levitt, R., and Carlson, R. (2002c). Formalization and Automation of Time-Space Conflicts Analysis, Journal of Computing in Civil Engineering, 16(2), pp Akinci, B., Fischer, M., and Zabelle, T. (1998). Proactive Approach for Reducing Non-value Adding Activities Due to Time-space Conflicts. Proceedings of the 8th Annual Conference Lean Construction, Guaruja, Brazil. Dawood, N., and Mallasi, Z. (2006), Workspace Competition: Assignment, and Quantification Utilizing 4D Visualization, Computer-aided Civil and Infrastructure Engineering, Vol. 21, Guo, S.J. (2002), Identification and Resolution of Work Space Conflicts in Building Construction, Journal of Construction Engineering and Management, 128(4), pp Kaming, P. F., Holt, G. D., Kometa, S. T., and Olomolaiye, P. O. (1998), Severity diagnosis of productivity problems - a reliability analysis, International Journal of Project Management, 16(2), pp Mallasi, Z. (2004), Identification, and Visualisation of Construction Activities Workspace Conflicts Utilizing 4D CAD/VR Tools, Proceedings of the 1st ASCAAD International Conferend, e-design in Architecture, KFUPM, Dhahran, Saudi Arabia. Oglesby, C.H., Parker, H.W., and Howell, G.A. (1989), Productivity Improvement in Construction, McGraw-Hill Inc, New York, NY. Riley, D.R. and Sanvido, V.E. (1995), Patterns of Construction-Space Use in Multistory Building, Journal of Construction Engineering and Management, ASCE, 121 (4), pp Riley, D.R. (1998), 4D space planning specification development for construction work spaces, Proceedings of the Intentional Computing Congress, ASCE, Reston, VA, pp Sanders, S.R., Thomas, H.R., and Smith, G.R. (1989), An Analysis of Factors Affecting Labor Productivity in Masonry Construction, PTI # 9003, Pennsylvania State University, University Park, PA. Thabet, W.Y. (1992), A Space-Constrained Resource-Constrained Scheduling System for Multi-Story Buildings. Ph.D. Diss., Civil Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA. Tommelein, I.D., Levitt, R.E., and Hayes-Roth, B. (1992), SightPlan Model for Site Layout. ASCE, Journal of Construction Engineering and Management, 118 (4), pp Tommelein, I.D. and Zouein, P.P. (1993), Interactive Dynamic Layout Planning, Journal of Construction Engineering and Management, ASCE, 119 (2), pp