An IFC Representation for Process-Based Cost Modeling

Abstract

One of the applications of BIM is for cost estimating in construction projects. However, the usual practices regarding the integration between cost and product models with BIM have been limited to the quantity takeoff of physical production measures from a digital model. The cost estimates of the building and its components usually happen outside the BIM model, through the same cost estimate method that has been traditionally used in the construction industry. Production costs are estimated based on previously known consumption rates of resources and theirs acquisition costs, which are commonly stored in external databases using “ad hoc” representation schemas, without any further information exchange with the BIM model. Nonetheless, the most recent version of the ISO 16739 standard (the Industry Foundation Classes, addendum 2, IFC4-add2) has included a number of new classes and properties aimed to extend BIM scope much beyond the product model. However, up to the moment, no specific schema using these new classes has been proposed in order to incorporate cost model information into the BIM model. This study was aimed to investigate the possibility of representing process-based cost information using IFC 4 objects. The research method approach used was case study. Some use cases of processes cost models were selected from real cost modeling cases, and generalize to design a process-based cost modeling schema in IFC. The resulting schema was then instantiated in a prototype, used to validate the logic and output of the representation against manual calculations. The representation of process-based cost modeling proved to be capable of successfully merging the cost modeling schema within a BIM model. It opens the possibility of close integration between product and cost models with BIM technology, as well as the storage and dissemination of cost models and their related information using open and interoperable representation.