A knowledge-based BIM exchange model for constructability assessment of commercial building designs
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At the early design stage of construction projects, designers often rely on general rules of thumb to make critical decisions about the geometry, construction systems, and materials used in their designs without fully evaluating the applicable construction requirements and constraints. However, ease of construction, or constructability, is a critical factor that is best examined at the early stage of construction projects when designs are the most amenable to change. Currently, reviewing a design’s constructability requires that designers spend a significant amount of time manually extracting constructability data from building models. Data extraction for constructability presents a challenging task, especially in large and complex projects, in which designers may neglect important data pertinent to, or extract unnecessary data from, their designs. The absence of a quantitative constructability model in the United States and a schema for extracting the necessary data for an automated constructability assessment of building designs motivated this study to develop a building information modeling-based constructability assessment exchange model. Through a comprehensive review of the literature, seventy-nine constructability attributes were first identified, which were then categorized into six groups using factor analysis based on 298 responses received from a questionnaire-based survey of industry professionals. Then using pairwise comparisons between constructability factors and common building systems used in the United States, a constructability assessment model was developed with the knowledge obtained from construction experts. Next, this study created a constructability exchange model (EM) using the United States National Building Information Modeling Standard™ approach to automate the data extraction required for the constructability assessment. The proposed EM identifies a reusable and consistent data set (e.g., geometry, object structures, relations, and properties) required for constructability assessment of building designs. The constructability EM was validated through an experiment based approach to examine if the model would help designers explore the constructability of designs in less time, assess the constructability of designs more accurately, and formalize the method of constructability assessment. We also validated the constructability EM using the IfcDoc application, so software vendors can use the EM to examine if their importers and exporters comply with the terminology and rule sets it defines. Moreover, domain experts can use it to validate their models to ensure they have all the required information for assessing constructability. Using the proposed constructability assessment model, designers can identify the tradeoffs involved in the constructability of various design alternatives and make informed decisions about any proposed changes. The constructability EM provides formal classifications of construction information that, when implemented, automates the repeated and time-consuming task of constructability assessment of designs.