upFront.eZine 1,089: A Contractor’s View of BIM (part i)
Guest Editorial by Matt Stachoni
The Business of CAD | 29 March 2021
I recently had the vice president of a large construction company tell me he thought that BIM was “generally a nice idea, but a waste of money and resources.”
At first, I was taken aback by his assertion, but after analyzing the current state of BIM on building sides, I realized that he’s absolutely correct.
It got me thinking how BIM directly and, perhaps more importantly, indirectly benefits the construction process. Understanding how BIM is currently used in construction reveals how often its practice is antithetical to producing beneficial outcomes.
For many construction firms, massive changes in thinking are required to properly implement BIM across projects of all types before real-world results are aligned properly to BIM’s potential and promise. As a side effect, proper implementation promotes BIM as a core component essential to every project at the very outset, where such consideration has the most impact and value.
The fact is that the way most contractors typically utilize BIM on today’s construction projects is downright idiotic and costly. The problems are deeply rooted on traditional shop drawing production and coordination efforts, and fails to take into account what BIM brings to the table.
I have identified four areas where BIM usually falls flat in practice; what gets in the way of realizing many of its benefits; and an outline of a relatively simple solution. But first, some background on how construction sites work.
How Construction Teams Work
To begin, I’d like to describe some background points to explain how building construction is carried out. This may be useful to those unfamiliar with how the sausage is made.
A general contractor (GC) is hired by the owner to build the project. The GC’s primary role is split between managing the owner’s requirements and expectations, and steering the project’s workforce through the entire process.
The GC’s office team is composed of a small army of project engineers responsible for directing the trade subcontractors and supporting field operations. They do this through holding daily meetings; processing submittals; writing, routing, and tracking Requests for Information (RFIs) and the answers to and from the design team; denying change order requests; checking the quality of the work done in the field; and so on.
The GC necessarily works with the architect and engineer of record to some degree. Every project larger than a doghouse will at some point have some contract issues to deal with. So how the GC interacts with the design team depends largely on the project delivery method around which the project is based. These are:
Design-Bid-Build Method. The GC starts work from a (more or less) complete set of finished construction documents, typically interfacing with the design team’s construction administration (CA) representative, who monitors the process and handles constructability issues.
Design-Build and Integrated Project Delivery (IPD) Methods. The GC partners with the design team, as well as the subcontractors from the outset, directing everyone from start to finish and continually working out construct ability issues throughout the building phase.
The Purpose of BIM on Construction Sites
Regardless of the project delivery method, BIM quickly becomes a center of attention, because on the construction site BIM at its core does one thing and only one thing only: It answers questions. That’s a hugely powerful tool to have.
Armed with a set of high-quality construction models, a fully BIM-enabled project engineer can answer almost any question anyone has about the project.
I can tell my wall framers to the millimeter exactly where on the slab the outside corner of the wall stud should be.
I can tell the mason where a 4” chilled water pipe sleeve -- whose size properly accounts for the insulation -- needs to be placed in a CMU [concrete masonry unit] wall, appropriately accounting for the bond beam above.
We can have the surveyors precisely locate every hanger insert installed in the concrete slab, before it is placed.
We can provide fully coordinated locations, sizes, quantities, and costs of all required access panels for hidden equipment, valves, conduit pull boxes, and other maintainable items installed above hard ceilings and behind walls throughout the project.
Used in conjunction with continual laser scanning of the job site, we can tell our plumbing subcontractor how off the mark their piping stub-up is, which is popping up out of the dirt in an empty area but intended to be centered within a 6” stud wall cavity at some future point. Or where we can core drill through a concrete wall to miss the rebar, which eliminates the cost of having a specialty subcontractor come in later to scan for it using ground penetrating radar.
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Sophisticated owners of large-scale facilities are getting in on the BIM action. They are demanding that the models include additional information which locates and identifies the building’s maintainable assets and so allow the Facilities Management (FM) group to extract Enterprise Asset Management (EAM) information automatically and drop it into their FM operations databases.
Of course, that kind of wow factor doesn’t come cheap or easy. However, the benefits are exponentially greater than the costs, and have proved ultimately invaluable to projects at large.
This then brings me to the four primary issues I have with BIM as typically implemented on the job site.
Issue 1: Getting BIM Into the Right Hands
To review conditions and answer questions, it does no good to have this deep project knowledge silo’ed away with one or two specialized people. In many construction firms, there is a dearth of BIM expertise among project engineers. But once superintendents or project managers get a whiff of what BIM can do for them, the demand on the few who can access models is overwhelming.
While every project needs a BIM manager to control the models and ensure they are accurate and available, every project engineer and superintendent needs training and hardware to interact with the construction models using the appropriate software. This can be Revit, Navisworks, Tekla, AutoCAD, Revizto, and so on.
Issue 2: Design Intent Models are Stupid
There are crucial distinctions between models produced by a design team and the kinds of models useful to construction teams. They serve two masters and so have different requirements.
Models produced by the design team are considered an Instrument of Service. They more accurately are termed “design intent models.” They are created solely to produce code-compliant Construction Documents, which are signed and sealed by the A/E [architect or engineer] and issued for permitting.
Modeling requirements for design intent are lower than that required for actually building projects. They do not have the appropriate level of 3D detail, nor are they accompanied by the correct manufacturer-specific non-geometric information needed to answer questions we need in the field. Indeed, unless there is a constructability review, most sets of CDs do not need any proof of buildability to pass muster.
I don’t think it’s a stretch to state that most designers may understand design but not necessarily construction. They do not possess practical construction experience. Construction teams see evidence of this in almost every set of design drawings, such as overly complicated and expensive details, impractical placements of components and room types, and contradictory information.
With regards to BIM, designers often leave out of the model things that taken care of in the details with simple 2D linework. That may be fine for their intended purpose. However, missing 3D content can easily end up being critical to the coordination and constructability of the design.
HVAC engineers competently design air systems that produce 200cfm [cubic feet per minute air flow] at a specific diffuser, but the mechanical piping may use fittings that are impossible for the size of pipe, or be routed through such tight spacing that it cannot be welded or installed by hand in the field. The structural designer may leave out supplemental steel or connection modeling that impacts the pathways of MEP [mechanical, electrical, and plumbing] services.
Typically, a designer says that such problems are means and methods issues, and so are the responsibility of the trade contractors. The trades then counter that they are forced to massively re-route their work, which is a design issue. Both are right, and both are wrong. The problem remains that the design intent cannot be built.
Design-intent models do not typically reflect what is ultimately going to be purchased, fabricated, and installed in the field. These occur only once the design is completed and the trades get their hands on the CDs. Nearly every item placed on a project requires a formal submittal provided by the trade subcontractor and approved by the design team. The submittal is the combination of what is dictated in the specifications and drawings, and takes into account the subcontractor’s understanding of and familiarity with the product, its pricing, availability, and other factors – information designers simply don’t need to consider during the design phase.
Issue 3: Working with Trade Subcontractor Models
Once the design CDs are issued and the GC and trades mobilize to build, the next round of BIM-based idiocy begins -- with the trade subcontractors.
Next week: Part ii
[Matt Stachoni is a BIM Manager/Senior Project Engineer with Tutor Perini/ Parsons JV, and works on very large design-build construction projects that rely on regular IFC model exchanges to owners.]
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And in Other News
Nanosoft releases nanoCAD Construction 20 ($260 and up) with new tools for construction engineers with a library of parametric 2D design elements useful for A/E/C:
Automatic numbering of objects
Text formatting controls in tables
Improved space objects
Added functions for manipulating IFC data
Download the trial version from nanocad.com/products/construction/download/
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Wohlers Associates has published Wohlers Report 2021 (375 pages) in the 26th year of its annual reporting on 3D printing, cataloging 124 service providers, 113 manufacturers, and 24 third-party producers of materials. COVID-19 caused additive manufacturing to grow by 7.5% to $12.8 billion in 2020, down from the average of 27% during the previous ten years. Learn more about it from report contributor Randall Newton at wp.me/p3IFfX-8m.
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Graphisoft offers PARAM-Q, a new built-in parametric object design tool for ArchiCAD Windows and MacOS to create building component libraries parametrically.
Predefined and customized Excel files automatically map manufactured profiles to SAF [structural analysis format] cross sections. Details through graphisoft.com/downloads/archicad/updates/ac24/up3.
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After three or four years in stealth mode, Riven [no, not the game] launches its hardware-software combo for checking 3D parts. You place green, sintered, or post-processed parts on a turntable “and hit the button.” The software compares the scanned part to imported CAD or golden-part scans, with heat maps showing deviations. Accuracy is 0.0002". More at riven.ai.
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Here is a post on my WorldCAD Access blog:
You can subscribe to the WorldCAD Access blog’s RSS feed through Feed Burner at feeds.feedburner.com/WorldcadAccess.
Letters to the Editor
Are you going to write any e-books for the BricsCAD V21? What’s your take on the program since the Hexagon takeover?
- Tim Neumann
The editor replies: Producing books depends on the need of Bricsys. At this point, it looks like they will be delayed until V22. I am not hearing a lot any more from Bricsys.
One emphasis I am hearing about is sales, no surprise given Hexagon is a huge organization. The program itself seems to be doing well so far.
Re: Q&A With the Inventor of Catia
I love this Ralph. Thanks.
- Kathleen Maher
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I enjoyed the interview. But I thought you might like the CAD user’s viewpoint.
Catia didn’t show up on the PC [personal computer] until 1998. Most of the ComputerVision users moved to Pro/E in the early 1990s, enjoying the standalone stations.
I was selling PC based 3D CADKEY to virtually every Boeing supplier to talk to the IBM networked based Catia 2, 3, and 4. Then I sold them CADKEY to translate Catia 5 files to import to Catia 4! Catia 4 had a 34MB limit and the files had to be modified.
Why? Catia 5 could not talk to Catia 4. Horrible for aircraft design! Boeing had 1,500 CADKEY seats. They could have been on PCs ahead of everyone. Remember ComputerVision, Catia 3, and CADKEY were 3D wireframe. Catia 4 came out with Boolean solids in 1994 (I think). CADKEY used ACIS in 1995!
- Joe Brouwer
The editor replies: There were so many hardware options in the 1980s, and prices were high, so spending $100 thousand or a million was a strong decision. Mr Brouwer recounts his history with CAD at tecnetinc.com/Cadkey%20or%20Catia.html.
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I did not know about Fastdraft. Its use has been quite marginal, but I found its history on page 10 of the following document: cadhistory.net/13%20IBM,%20Lockheed%20and%20Dassault.pdf. Thank you, Ralph, I like the pictures you added, the Mirage and the IBM 360, as they illustrate well the text.
- Francis Bernard
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Interesting articles, thanks. One thing I was told when I was at Dassault: that when IBM saw what Dassault Aviation had [with Catia] they knew it would kill CADAM. Not sure if it is true, but it makes sense.
The editor replies: I love history, so getting this Francis Bernard interview from David Levin was much appreciated by me.
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Lunchtime peruse of non-work emails reveals upFront.eZine interview with the inventor of CATIA part 2: "Bernard Charles, who joined Dassault Systemes in 1984, who became technical director in 199, and then CEO in 1995. An ambitious leader with a very large ego.”
- Kevin Quigley (via Twitter)
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Possibly, but the man has vision in spades, it just takes a while to deliver on them.
- Martyn Day (via Twitter)
Mr Quigley replies: And a difficulty in communicating the vision in a language or format customers relate to or wish to go along with. Vision without clarity of message is just fog.
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I heard him speak at many Solidworks Worlds. His visions never seemed aligned to what we, the users, wanted/needed as far as Solidworks is concerned. Not sure how he came up with his vision, but it wasn’t from talking to users.
- Jeff Mirisola (via Twitter)
The editor replies: It is a top-down vision. Dassault is so successful in its niche of high-end CAD that execs cannot fathom why Solidworks users spent the last decade rejecting “Solidworks V6” and its subsequent CGM-based variations.
“It’s easy to discard an entire field of centuries-long academic inquiries, especially if you’ve never been exposed to it, or only investigated a caricature.”
- Joakim Book
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