Thursday, 29 August 2013

BIM and LOD

One of the most talked about topics around BIM is always LOD. This can stand for a number of things and maybe Level of Development is better than Level of Detail as "detail" could be seen to be about geometry only. This level of development can perhaps be thought of as a combination of the detail (the graphical content) and the information (the non-graphical content).

The recently published PAS 1192-2:2013 defines the following abbreviations:
A.77 levels of model detail (LOD)
Description of graphical content of models at each of the stages defined for example in the CIC Scope of Services.
A.78 levels of model information (LOI)
Description of non-graphical content of models at each of the stages defined for example in the CIC Scope of Services.
Information model development through the digital plan of work
Figure 21 of the PAS shows this level of graphical and non-graphical information slowly developing throughout the project (alongside additional documentation). Figure 20 in the PAS gives examples of what type of information may be present in the overall model at each stage of the digital plan of work.

In the USA...
Meanwhile in the USA, there has been some movement on this recently. Most notably through BIMForum, a multidisciplinary group of BIM users, who have just released their Level of Development Specification. Building Design + Construction Magazine posted a review of this at the website below:
http://www.bdcnetwork.com/level-development-will-new-standard-bring-clarity-bim-model-detail

The BIMForum launch presentation for this video can be viewed on youtube...

The three aims of this document are (1) to help owners when they want to specify what information they want and when, (2) to help design managers explain this and (3) to have something that can be referenced in Project/BIM Execution Plans.

The document notes some interesting caveats, notably is that different objects in the model will develop at different rates (for example structural objects will develop faster than interior objects) and therefore the overall model cannot have a "LOD".

Some examples from the document are below...
BIMForum LOD guidance for structural frame
BIMForum LOD guidance for cooling system
Going further a field than just the USA, some more information on what is happening on this subject around the world - please check out the following excellent blog post by Antony McPhee
http://practicalbim.blogspot.co.uk/2013/03/what-is-this-thing-called-lod.html

As example of what NATSPEC in Australia are doing with their National BIM Guide is below.
http://bim.natspec.org/index.php/natspec-bim-documents/national-bim-guide
This NATSPEC National BIM Guide is an adopted version of the US department of Veteran Affairs (VA) BIM Guide:
http://www.cfm.va.gov/til/bim/BIMGuide/
NATSPEC LOD derived from the VA BIM object element matrix
The VA BIM Guide
...So what are NBS doing?

1. Classification
Internationally, the standard ISO 12006-2 defines classification for construction objects. This defines the principles for tables that are classify items such as entities (eg. school), spaces (eg. class room), elements (roof), systems (clay tile covering system) and products (clay tile).
UK - http://www.cpic.org.uk/en/uniclass/new-uniclass-proposals.cfm
USA - http://www.omniclass.org/background.asp

These classification systems allow objects to to start "big" and then as the project progresses to be broken down into smaller object as the information develops.

NBS are members of CPIC and are helping finalise the Uniclass 2 classification tables. We have also created a Uniclass mini-site and this includes a presentation from John Gelder NBS who sits on the task force for review of ISO 12006-2.
http://www.thenbs.com/uniclass/


2. RIBA Plan of Work 2013
The RIBA Plan of Work 2013 was published earlier this year.
http://www.ribaplanofwork.com/
As part of Stage 1 Preparation and Brief, one key task that should take place before design begins is the production of a Design Responsibility Matrix.
Design Responsibility Matrix
The associated RIBA publications, Assembling the Collaborative Project Team, will give detailed guidance and template tools to help project teams produce this document. In terms of the associated template tools, NBS are currently working with the publication's author Dale Sinclair on the production of these tools. A sneak preview (caveat - subject to a  few tweaks before release) is below...
Template Design Responsibility Matrix 
This is a guidance template - and it must provide support for all projects and not just BIM projects. The design items on the left hand side are completely editable. At the start of the preparation stage these items will be high level probably describing elements, but as the concept design stage ends and the developed design stage starts these will be expanded to cover the systems and products that have been selected to satisfy the brief.

In terms of the drop down values, these can be modified (for example, to use AIA LOD definitions), but out-of-the-box, to cover the majority of projects in the UK, the values include a scale for the drawings drawn or exported from the model and an indication of whether the design is an outline description, or describes performance, generic specification of products or proprietary specification of products.

The book Assembling the Collaborative Project Team will be available from October 2013 from RIBABookshops.com and then templates will be available to download from http://www.ribaplanofwork.com/.
The preparation stage is crucial prior to the three design stages commencing
3. National BIM Library
http://www.nationalbimlibrary.com/ is the NBS free-to-use library of standard BIM objects. These include objects at three broad levels of development.
Concept objects that allow the basic shape and room usage to be defined
Objects representing typical generic constructions without considering material properties

Manufacturer objects that contain all properties of an object representing the real-world item
4. NBS Create
At NBS we consider BIM to be much wider than simply the design model. The specification and the property sets within it make up a significant percentage of the "i" in BIM. With NBS Create the information can be developed in parallel with the design model.

Consider the example below looking at a deck system...
At concept design stage - their may be just a simple description of the system
As the developed design stage begins an outline of the products can be added
As developed design continues, the overall performance of the system may be added
During the technical design stage, individual products and their property sets may be specified
...and finally, a manufacturer product is always chosen by one of the parties (client, designer, contractor, sub-contractor)
5. Support to BIM Task Group
NBS worked with the BIM Task Group to define the information requirements for around 20 objects based on the MofJ plain language questions.
The labs area can be accessed here:
http://www.bimtaskgroup.org/task-group-labs-portal/
What information is needed, what is its definition and when is it needed?
A blog post I did at the time looking at this can be viewed here:
http://constructioncode.blogspot.co.uk/2013/03/bim-task-group-labs-area-overview.html

The consultancy exercise around the labs work is still under-way - but the feedback and next steps will be very interesting.

So quite a complex subject - and definitely one that needs further refinement and discussion. But hopefully this blog post gives some food for thought on how information will develop through a BIM process on a project.

4 comments:

  1. Hi Stephen,
    just went back to read this blog-post again. What I was wondering how the NBL deals with the LOD issue. You write, that the NBL includes "objects at three broad levels of development". But does that mean, that you would have to download three different objects to get the mentioned three different LOD?
    Looking at other examples like Hilti (http://hilti.cadclick.com/?mandant=GB&laid=101), they differentiate between 'high detailed' and 'simple detailed' (I'm not sure if that's correct English, is it?). But that's not how the NBL does it, or am mistaken?

    Thank you for your answer! All the best from Berlin! Konrad Stuhlmacher

    ReplyDelete
  2. Hi Konrad,

    I've been meaning to do another blog post of LOD, progressing and plans of work. But to as a quick reply to your question on National BIM Library objects. Here are three example types of objects:

    1. Concept object - this allows you to simply define spaces so the designer can concentrate on the design of the spaces in the buildings.
    Concept roof

    2. More detailed object - these have material build-ups as typically used in the UK construction industry. The property values are generally empty, the user can fill these values as the project progresses.
    Generic type of flat roof

    3. Proprietary object - these have the actual material build-ups from a specific manufacturer. Most property values are complete. The user can fill the final values for items such as installation date.
    Flat roof from a specific manufacturer

    ReplyDelete
  3. Thank you very much for your quick response!

    ReplyDelete
  4. Hi Stephen,

    sorry to ask again: How would I find the concept objects within the NBL? As far as I can see, you can browse by object type or by manufacturer. Once you've selected an object type you can then filter by object type (generic/proprietary) and/or the manufacturer. But there isn't a possibility to look for Concept objects, is there? Thank you very much for your reply! All the best from Berlin! Konrad

    ReplyDelete