Aug 19, 2021Liked by Brian Potter

To expand on your "every new detail is a potential error attack surface" remark, fear/risk of litigation is another key obstacle preventing BIM from taking hold completely. The actual contract documents are almost always 2D. Designers may send 3D models to the contractor, but only after the contractor signs a release acknowledging that the drawings are the source of truth.

I believe this is due to the lack of change control and potential for ambiguity in BIM. Revision clouds provide straightforward change control for 2D documents. In the case of a dispute, 2D drawings make it easy to see exactly what the design team provided to the contractor; the contract line is clear. Not so for BIM. Even if you can effectively enshrine a specific model version as the single source of contract truth (no small feat), models contain so much information that it's difficult to clearly communicate the design intent. E.g. between different worksets, design options, links, views, hidden elements, etc. there will inevitably be some confusion regarding design intent.

Said another way, designers are well-practiced at quality control and CYA in 2D drawings but BIM allows too many loopholes.

The Gehry Technologies example you mention above is the exception that proves the rule. Seattle's Experience Music Project (now "MoPop"), built way back in the mid/late 90's (!!!), lived the BIM dream: the Catia model was the source of truth, contractually and in practice. I have heard that the model was so detailed it contained the screws securing the light switch face plates. This ultra-detailed model was at the center of an atypical contract that included a ~20-step flowchart detailing the project's information flows. I suspect that this worked because the owner had deep enough pockets to A) pay for team members to hire Catia specialists from Boeing and B) make sure all parts of the team made money, reducing the overall risk/litigiousness.

Perhaps BIM's fate is tied to that of another perennial next-big-thing: Integrated Project Delivery (IPD).

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Aug 19, 2021Liked by Brian Potter

Another proposed benefit of BIM that I see pushed--my slice of the world is heavy civil works (dams, etc.) for the US Government--is the ability to keep the BIM database as a single source of truth through the project life, assisting in maintenance and further work. That is, if you want to do a contract for maintenance work or modifications for new requirements, you can use the BIM system to support that work and to create new contracts.

The problem with this workflow is that now, somebody has to maintain that model throughout the life of the project, and without that effort the model can turn out to be worse than useless. We've been 3D for years, though not BIM, and we've found that even the dumb 3D geometry can be very fraught for reuse. When you go into project files and pull a 3D model to start a new job, *exactly* how much do you trust what that model says? In several instances, we've ended up creating a whole new 3D model for newer modification contracts, just because we couldn't be sure of the accuracy of the model created, say, 10 years prior for another job, and doing detailed checking against the drawings to validate the model can be as extensive an effort as creating a new one. (And even opening something that old can be a real challenge, given that backwards compatibility doesn't always seem to be a priority for software--paper, and to a lesser extent PDFs and images, always work in the future unlike gee-whiz tools.)

Granted, we have a very different environment than what you're discussing here. Almost everything I've worked on is modification to an existing site from decades before computers were widespread, rather than new-build. This does make it even more challenging overall, because instead of a model done right at construction that you can reasonably be sure was complete like what you're discussing in the OP, budget limits often mean a model was created just with the extents of the work and maybe a little bit beyond, and the limits of the work where more detailed effort was put in won't always be obvious to a future design team.

For example, I've been working on a project modifying an intake tower for a dam (think "underwater skyscraper", which draws water into outlet works and a powerhouse and has infrastructure to access the gates way down in the depths of the reservoir so you can perform that work in the dry). The modifications were mostly occurring on one exterior face. We had no 3D model for the existing structure, so we had a technician start creating a model from the as-built sets, which consisted of two large projects (the original construction in the '50s, and a major modification in the late '90s). However, since we were only modifying one side, most of the effort in modeling the 3D geometry went into the area we were modifying. For example, just due to timeline and budget limitations, I told the technician to not model stairways and very significant steel platforms inside the tower because we weren't touching them. Even the water passages we elected to just stop modeling about 5' from where they leave the tower.

But that means that if somebody wants to use this model in the future for modifications inside the tower, they'll have to know that it's incomplete and what was left incomplete. My technician is very good about making sure he does one two things: 1) model something completely accurately to the as-built drawings, or 2) not model it at all. This does mean that, say, for the stairways a future user will see them missing and know they have to be modeled. (The missing platforms are something they'll have to know about, though.) However, not everybody is like this! Some people, in the past, have done stuff like just fake in stairway geometry since they're not going to touch it so it "looks right" on e.g., section cuts, and that's not always immediately apparent. So you have to approach a model with a healthy sense of distrust.

The other limitation, which may be similar to what you see in the private sector, is that the people who are technically responsible for maintenance of "as-builts," to include any models, would be our Operations staff, who are in a position very similar to Owners in this respect. But if they're not making sure that *everybody* touching the works in the model actually *uses* the model, to include their own maintenance personnel, even a technically-complete model can drift significantly. Generally for smaller work there's a tendency to just do a new small set of drawings for modifications, or for very small stuff, to just redline the existing sheets. But they're unlikely to put in the effort to then feed this back into the model, so no matter what you're not getting away from extensive reliance on integrating multiple sets of drawings as part of the work.

Not to say that this is just a problem for 3D models/BIM, of course! You run into integration, unknown modifications in the past, and as-built differences in paper drawings. It may just be me used to working with paper drawings, but it "feels" harder to find these differences in a full model, since as you noted you can radically change what you see via different views.

But it's much cheaper and easier to work with the paper drawings using the Mk1 Eyeball, as opposed to groveling through a 3D model to figure out what's going on. The question is, "Will this become cheap and easy enough to make it worthwhile to transition to a model as the main way of maintaining data?" We've kicked around transitioning to BIM in our office for years, but as you've noted, there's a real resistance to change, in this case, because of the possibility of spending a bunch of money and not actually ending up with a workable product. The only way to be sure to succeed is to spend a huge amount of money creating models and the infrastructure to maintain them, but that also means that if you fail you've wasted huge amounts of money, and those of us working in government service aren't unaware of how bad we are at IT as an organization.

I'm not sure how well many private owners can really do this either; having a guy maintaining and managing a Revit model feels harder and more expensive than having a set of cabinets in the basement with paper drawings, or even maintaining a folder on a hard drive with PDFs or scanned images. Admittedly, I'm limited here because all of my experience is in the federal government with very different constraints and internal politics.

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Any comments for Digital Twin system like Bentley System..?Thanks ..Great writing ..very interesting ...

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Thanks Brian, although your optimistic close took me a bit by surprise. Especially since your follow up post on the complexity of construction points to the remarkable challenges at automating the AEC industry.

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1. One problem with BIM is that the knowledge necessary for a correct and detailed model does not exist in a single place, and certainly not in the design team. The distance between "design intent" and "build it exactly this way" is very long and full of risk and complexity. It is hard to overstate the importance of this.

2. One reason that IPD (Integrated Project Delivery) is such a big help in successful BIM-centric projects is that it gathers the knowledge (or the people who have the knowledge) together early in the process.

3. Twenty years ago I wrote a guest editorial in a CAD blog (upFront.ezine then, now https://worldcadaccess.typepad.com/) and it turned out to get lots of responses. Short story:

Leo Schlosberg wrote a guest editorial for upFront.eZine #256 in which he asked, "Does CAD Degrade Drawing Quality?" His core argument was this:

In the same period of time that CAD came to replace the pencil as the primary drawing tool, the coordination of construction drawings (which I informally measure as the coordination between the architectural drawings and the structural drawings) got worse. This is counter-intuitive. I have, however, never met anyone who argues the fact.

And so this newsletter received more letters on this topic than any other, with the consensus being, "Yes, CAD does degrade drawing quality." The problem was not with the software itself, readers said, but that new users were being trained to enter commands to run software -- instead of learning drafting conventions, as was taught in the days of hand drafting.

4. If you want more of my blah-blah on the role of knowledge in construction, see http://caryconcrete.com/writings/Schlosberg%20Presentation%203-31%20notes%20reduced%20for%20speaking.pdf

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Not only is it unknown and difficult to manage changing information, but the information that is presented by manufacturers has an inconsistent format. When interviewing various plumbing designers at the ASPE show a few years ago, the chief gripe was that BIM is hit or miss because each BIM model needs to be cleaned up and reformatted into what their firm uses. Being in the standards and certification world, my lens to solve this issue seemed completely appropriate. I hadn’t the first clue where to start and more to the point, how was the effort to unravel and agree upon what is “standard” on a plumbing part going to fit in with a business case?

Fast forward 3-4 years and now I am back at a manufacturer and am looking to fit into this world. What do I publish in a Revit file that has sufficient information and of the appropriate format that provides the maximum good for the AEC industry? Clicking through your link to IFC took me to ISO 16739 https://www.iso.org/standard/70303.html , which also appears to be here https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/ . I thought this was the eureka moment, but that does not appear to give a specific metadata format to follow as that would be too narrow for a standard. This then (probably) requires going through each instance of a product type that fits in with the MasterFormat list from CSI. Having that standard spec metadata format is really what I’m looking for. If folks out there have any hints on that, please reach out. https://www.linkedin.com/in/conrad-jahrling/

This is a great article, btw.

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everything you write is gold.

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