Essential Terms in BIM Practice
While I was trying to capture fancy BIM topics floating around my head, the blog chief editor brought this topic, and it is a very good idea. Actually, we have a similar chapter in the BIM Execution Plan.
It is useful to know some essential terms in BIM practice for easier understanding of upcoming BIM articles in this blog. I picked the terms in our BIM practice mainly use Autodesk Revit and BIM 360.
BIM (Building Information Modeling)
You may already know what BIM is however let me start with the easiest one. BIM stands for Building Information Modelling. In simple terms, BIM is the 3D geometry with information embedded to the element. So, it allows us to develop the design and visualize it and we can see the attribute of components what they are. From this information, we can perform design reviews, analysis, engineering, interdisciplinary coordination, production of 2D drawings, data output, and various uses for the project lifecycle.
“BIM Requirements” is where BIM became the “Mandatory Requirements” for the project. This document is a part of the RFP (Request for Proposal) prepared by the Employer/ Project owner to hire a designer/ a contractor.
I noted that “BIM Requirements” was documented variously in my previous construction tendering projects. Some employers issued their BIM Standards then the contractor is to comply with it. Others included EIR (Employer Information Requirements). Sometimes, it is a generic document or project-specific documents.
How this document was named or formed in the RFT; this document must define the BIM technical requirements, BIM management requirements, BIM facility and BIM deliverables and so on. To prepare adequate BIM proposal, it is essential to understand BIM requirements and clarify ambiguities.
We have been working with designers and contractors in Japan and they use BIM for some project as it is essential for the project delivery. In those cases, we set the project BIM goals and scopes to prepare BEP.
BEP (BIM Execution Plan)
BEP describes how BIM will be executed for the project therefore this is a project-specific document. The BEP drafting starts from the BIM Requirements given by Client therefore if you have a good understanding of the BIM requirements, you can produce an adequate BEP. There are typically two steps as below,
Preliminary BEP outlines a tentative plan and partially fixed sections in the document depends on BIM requirements. Sometimes designer/contractor needs to submit preliminary BEP as a part of the technical proposal then complete BEP after the scope award.
BEP is a fully developed document from the Preliminary BIM Execution Plan therefore it can be named as just BEP or Full BEP or Detailed BEP or something else as it agreed in the project team. It can be updated for a certain period at the beginning of the project as per BIM Requirements and this is the record to explain how the BIM model and its deliverables were done at the end of the project.
For BEP samples and further readings, you can find from the links below,
BIM Execution Plan (Architectural Institute of Japan, 2016)
BIM PROJECT EXECUTION PLAN VERSION 2.0 ( The buildingSMART alliance)
BIM Project Execution Planning Guide – Version 2.2
LOD (Level of Development / Detail)
Let me be straightforward to explain this! BIM model is 3D geometry plus embedded information which we develop throughout the design stages. We have a simpler 3D geometry and the lesser information at the Planning, Schematic design stage then we develop further at the design development stage. LOD defines the levels of this for each building element. LOD 100 contains the simplest information then it gradually increases up to LOD 400 then LOD 500 is an optimized version for use of BIM in the facility management (F/M) application.
The LOD 350 is about the interface with other building elements. We can specify some selected building elements while the majorities are at the LOD 300 for the Design Development stage. As an example, a project has a featured exposed structural design with the bespoke fine connection details to the structural members, then the designer will develop the relevant elements to LOD 350 to maintain design intention.
We often use “Level of Development Specification” published by BIM forum, US as a reference and it is widely referenced worldwide. The latest version is December 2020, and it is free to download. https://bimforum.org/lod/ Please do check it out!
MPS (Model Progression Specification)
MPS is a standardised building component breakdown structure table/matrix that defines the LOD of components required for each design and construction stage as per the scope of works. We customize the MPS and LOD to suit for project requirements. The partial sample is as below,
CDE (Common Data Environment)
CDE is where BIM models and all project documents stored for the project team members to access and collaborate their works therefore it is the core facility for BIM as a working process. CDE can be a cloud-based or an on-premise server. One of the recently completed projects was done in BIM 360, the cloud-based CDE. It provided a quite effective way for the whole project team as we were forced to work remotely by COVID19 pandemic.
We started with setting the folder structure and assigning access permission for individuals that aligns with Project Collaboration and Communication Plan in the BEP.
Project Collaboration and Communication Plan address followings,
• Information Exchange Process as project team used speciality software.
• Model publish / package,
• Coordination model and Clash detection,
• Communication protocol.
Firstly, BIM Authoring is not BIM Modelling as BIM modelling is only a part of BIM Authoring. On the top of 3D geometry modelling, BIM Authoring includes a wider range of processing work like the input of model attribute, integration, extraction of design information (2D drawings, schedule and data) that supported by authoring tools in BIM software such as Revit, ArchiCAD etc.
Please see the quotation from BIMのかたち Society5.0へつながる建築知, 日本建築学会.
The act of accumulating and integrating building components as objects, and constructing and editing part or all of them as a BIM model. The act of adding new information or creating new values based on the BIM model. It also includes the extraction and creation of documents, such as drawings, from the BIM model as required for each phase.BIMのかたち Society5.0へつながる建築知, 日本建築学会 p220
Central model is a term in Revit software that saved on Revit server or BIM360 and Local model is to be synchronized to the central model. Mark-up and issue within each discipline are written in this model. It is saved in each discipline folder and only accessible by its team.
Sharing the central model at the dedicated folder in BIM collaboration platform. This process includes design validation and model QA/QC by each discipline leader.
Master Model is the model linking all discipline central models packaged. Mark-ups and issues to other discipline are written in this model. The Master model can be used for design review and check through overall progress.
When we use Navisworks to perform clash detection, we prepare coordination model linking the central models then set the rules to run clash detection. Scene environment, saved view, clash detection result, favourite view including comments and writings can be saved.
Clash detection is the most important part of spatial coordination in the BIM process. It identifies the clashes in the single-discipline model and multi-discipline models set by clash detection matrix.
- Hard Clash
Automated clash detection identifies the multiple objects occupying at the same space.
- Soft Clash
A soft clash refers to objects that demand certain spatial/geometric tolerances or require clearances for safety, maintenance, accessibility, installation, or other reasons.
BIM Dimensions (4D BIM, 5D BIM etc)
The basic of BIM model is the 3D geometry (with information embedded) and we perform design coordination and production of design information, then linking the additional dimension we can extend the use of the BIM model. The typical definitions of BIM dimensions would be as the table below.
From my past experience, I noticed that the definition of BIM dimension was different (or slightly different) by the employer (particularly beyond 5D BIM) therefore it is recommendable to clearly define in the BIM requirements when the project required XD BIM. You can see a related article with https://www.designingbuildings.co.uk/wiki/BIM_dimensions
IFC (Industry Foundation Class)
IFC is a file format to enable information exchange between different software. The format was developed and maintained by buildingSMART. Many BIM software support for import and export of IFC format.
buildingSMART is an international authority creating and developing BIM standards, BIM compliance, Awards, hosting international BIM events and other activities. Https://www.buildingsmart.org/about/who-we-are/
COBie (Construction into Operation of Building information exchange)
COBie is a spreadsheet-style database rather than graphical data to transfer asset data for the use in facility management. The information typically includes equipment list, datasheets, spare part, warranties, maintenance schedule etc.
For further readings, you can check following link https://www.thenbs.com/knowledge/what-is-cobie