Directed Representative Graph Modeling Of MEP Systems Using BIM Data

Building Information Model/Modelling(BIM)is widely used in all phases of the building lifecycle,and has become a new paradigm for the lifecycle management.Building operation and maintenance(O&M)is the longest phase of the building lifecycle,it’s effective to ensure the healthy operation and maintenance of a building.Mechnical,Electrical and Plumbing(MEP)system is the lifeblood of a building and play a vital role in the healthy operation of the building.In smart buildings,BIM and Internet of Things(IoT)integration can realize the intelligent monitoring of MEP systems and serve energy saving(e.g.,the air conditioning)and safety management(e.g.,the firefighting).In fact,the complicated spatial structure,large scale,and unintuitive drawing marks,all of which make it hard to monitor the MEP systems effectively.Meanwhile,the logical connection relationship of MEP system is an important part of BIM information.Due to human design errors,connection errors often occur in the BIM model,which affects the extraction of logical connection relation of MEP system,resulting in low operation and maintenance efficiency.Moreover,the existing monitoring system still needs improvements in data visualization and real-time.To address these problems,this study proposes the directed representative graph model of MEP systems using BIM data.Firstly,the representative edges and the logical connection relationships between MEP elements are extracted from MEP systems,and combines the two to extract a directed representative graph of the building MEP system.Secondly,the directed representative graph is repaired using the upstream and downstream direction relationships between MEP elements.Finally,a visualization platform system is developed to integrate the representative graph model with IoT to visualize and monitor the MEP building system in real time.The main contents and contributions are as follow:(1)The scheme for the extraction of the representative graph is proposed.This section contains two parts,the representative edge extraction and the topological connection relationship generation.Firstly,the MEP elements are converted into triangular meshes to extract the representative points,and then these points are connected in turn to obtain the representative lines.Then,the spatial topology and semantic information between MEP elements are extracted from IFC files of BIM models,and the connection relationship between adjacent MEP components is identified to obtain the direction and realize the visualization of MEP systems.(2)The method of direction correction for the directed representative graph is proposed.Firstly,the representative edges of the devices are removed from the representative graph,and a collection of disconnected pipe representative edges is extracted.Then,the pipe representative edges collection is separated,and the removed devices are reconnected to the collection,constructing a subgraph of the representative edges collection with devices.Finally,the flow direction relationship between the devices is used to correct the direction of the representative edges,so as to obtain the correct directed representative graph.(3)The visual application system of building MEP is developed.The directed representative graph model and IoT technology are integrated to build a visualization system for building MEP system based on the BOS platform.Different element symbols are used to replace the medium velocity,flow direction and category of the MEP system.The data monitored by the sensor is transmitted to the database and updated in real time,which can monitor the MEP system intelligently.Overall,this study proposes a BIM-based directed representative graph model.This model lays a solid foundation for the development of monitoring MEP systems in smart buildings and promotes the further development of BIM in O&M management.