Study On Automatic As-bid Cost Estimation For Construction Projects Based On Design BIM Model And Ontology Technology

As-bid cost estimation for construction projects is one of the most important aspects for participants since it is the basis for cost control and contracts.Fast and accurate as-bid cost estimation means short biding periods and effective cost control in construction projects,which is the aim of both tenders and biders.However,subjected to the poor ability to express design result in 2D drawings and the inefficient workflow,the traditional as-bid cost estimation is labor-intensive and error-prompt so that cost estimators have no time for cost control at higher levels.With the advances of Building Information Modeling(BIM for short hereafter)and ontology technology,it is possible to achieve automatic as-bid cost estimation.Some researches on semi-automatic as-bid cost estimation based on BIM and ontology have been carried out.In these researches,BIM is utilized to share cost-related information between different stages of the construction projects while ontology technology is utilized to semi-automatic process of cost-related information with reasoning support.In order to achieve efficient and accurate as-bid cost estimation,this study proposed a method for automatic as-bid cost estimation based on design BIM model and ontology technology.Focusing on the as-bid cost estimation with bill of quantities,the study was carried out in three parts including a)system framework and information models,b)key mechanisms and algorithms,c)and prototype system and application.Firstly,based on existing researches on semi-automatic as-bid cost estimation,the possiblility of full-automatic as-bid cost estimation was discussed and a system framework for automatic as-bid cost estimation was proposed.Then exsiting information models for as-bid cost estimation were improved accordingly.Secondly,standards of cost estimation were analyzed to summarize missing information when using design BIM model in the as-bid cost estimation.Based on the analysis,a mechanism to fill missing information automatically for as-bid cost estimation was established so that manul operations could be reduced.Finally,by selecting and utilizing existing freeware components,a platform for rapid software development of reasoning applications based on BIM,i.e.BIM-R platform,and a automatic as-bid cost estimation propotype system,i.e.BIM-Estimate 3.0,were implemented and tested in 4 construction projects.It is found that,based on design BIM mdoel and ontology technology,as-bid cost estimation can be carried out automatically with few manual operations so that the cost estimators can be freed from cost estimation and pay more attention to cost control at higher levels.