Keywords: constructability conflict, schedule, integrated product, process model, resource model, simulation, inference engine.

The increasing complexity of AEC projects demonstrates that the constructability analysis of the entire project is a critical issue for the success of AEC projects[1,2,3]. One of the key opportunities to improve constructability lies in developing construction planning. The segmented project schedules, provided by several project participants, often include conflicts when they are merged together. The constructability review will provide a timely feedback to the constructors of the potential problems that might result from improper construction sequence. This feedback will help to redesign the project or re-sequence the activities in order to minimize plan conflict, to improve construction productivity and to streamline progress.

The main challenge for the different constructors in their communication with each other lies in the dependency between their activities which is affected by many factors like the state of the building component, the availability of information, and the construction space. The relationships between components and activities, between components, between resources, and between components and resources all exert extra constraints on the dependency between activities. So more elements should be added to integrate the project management information model for constructability review. . The Component State Model (CSM) proposed herein will integrate the extended 3D-product components, process activities, and resources into one model for constructability analysis.

The CSM includes 5 main parts, including (1) extended product component, (2) general component state library, (3) construction process, (4) construction resources, and (5) activity type library. In this model, the scope of component is extended to include temporary and site components besides permanent building component. The general component state library mainly stores a series of intermediate construction status of every component type needed by the project. This intermediate state information is very important for constructability review, for they form a main part of the activity triggering criteria. Additionally, the traditional view of resources comprising labour, material, and equipment should be extended to include construction space and information. Moreover, the merged schedule should not only list explicitly the construction activities, but also include the key implicit activities like logistics activities, information related activities, and space management activities.

The model employs the activity type library (ATL) to represent the construction knowledge for the activity. The activity type library in the model links the activities with both the states of the building components and those of the space resources, and forms the constructability criteria for the analysis. The inference engine uses the information stored in the activity type to verify the triggering criteria and changes the states of the respective product and resource components. The inference engine will attempt to match the criteria with the current states of the respective components and resources relevant to the activity. If the criteria of the activity can be fulfilled, the start of the activity can be triggered. The triggering will subsequently update the states of the respective components and resources at the start and also at the end of the activity. These changed states, which are the results of the triggered activities, will make up the prerequisites for other succeeding activities. If the criteria cannot be matched, the start date of the activity will be postponed and the conflict recorded.

This paper also discusses the main method to integrate AutoCAD and MS Project in the developing prototype, Integrated Product System for Constrcutability (IPSC), based on the CSM. At the end of this paper, the application of the IPSC is illustrated using an example to show the constrcutability analysis of the interaction between pipe installation and wall plastering activities to determine the potential constructability conflicts.

1

Construction Industry Institute, "Constructability: A Primer" Publication of 3-1, The University of Texas at Austin, 1986.

2

Construction Industry Institute, "Constructability Concepts File" Publication of 3-3, Bureau of Engineering and The University of Texas at Austin, 1987.

3

Construction Industry Institute, "Guidelines For Implementing A Construcability Program." Publication of 3-2, The Construction Industry Institute and The University of Texas at Austin, 1987.

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