A Contractor’s View of BIM (part ii)

Issue #1,090  |  Happy Dyngus Day! | 5 April 2021

 

Guest editorial by Matt Stachoni

 

Last week, in upFront.eZine #1,089, Mr Stachoni covered these points in his contractor’s view of BIM:

• How Construction Teams Work

• The Purpose of BIM on Construction Sites (it answers questions)

• Issue 1: Getting BIM Into the Right Hands

• Issue 2: Design Intent Models are Stupid

In our Letters to the Editor section below, lots of responses from readers to part i!

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Issue 3: Working with Trade Subcontractor Models

Once the design CDs [construction documents] are issued and the GC [general contractor] and trades mobilize to build, the next round of BIM-based [building information manager] idiocy begins -- with the trade subcontractors.

Almost every trade subcontractor goes through a lengthy shop drawing process. It replaces the design intent with fabrication parts and real-world details to make it buildable. Like the design team, shop drawings would ideally “fall out” of their modeling efforts.

But while trade subs may understand how to build, most have a real issue with modeling and will do the bare minimum to get the shop drawings out and approved. They often use non-BIM or semi-BIM (read: 2D CAD) methods for production, use incompatible software that doesn’t interoperate well with others, do not model with the appropriate amount of 3D geometric detail, and rarely populate components with essential non-geographical information.

Modeling in context is also a problem. Ideally, during this production phase, all modeling should be done in coordination with the other trades, such that the shop drawings are immediately ready for submission to the architect/engineer of record.

Here on planet Earth, however, all trades work within their own reality-distortion fields. Each has its own discipline-specific physical constraints to contend with, and so they tend to model their work so that it takes priority over the others nearby. During the coordination phase, they expect everyone else to simply move out of the way.

 

Issue 4: Coordination Phase

Once the trade modeling is largely complete, the GC and subs [subcontractors] undergo a lengthy coordination phase, in which clashes of trade models are checked against the other in an extended tug-of-war to determine who moves what. Each week, the trades submit models, the clash tests are run, and the clash reports are issued to everyone. The trades take these back to the office, rework the areas in question, re-submit models, and in the following week everyone rinses and repeats. Add in dealing with the myriad software interoperability issues, and the delays between creating a clash and resolving it become way too long.

The goal is to produce one area of work that the GC performing coordination can sign off. After that, the only thing left is to hope that the installers put everything where the shops had specified. (But that’s another story.)

 

Today’s BIM Workflow is Crazy

In this traditional approach to BIM implementation, we have designers creating redundant, basic design-intent models which likely can’t be built. The trade subcontractors create suboptimal models in a vacuum and run roughshod over everyone else. The GC shoves the trade Hatfields-and-McCoys in a room and forces them to play nicely together, identifies and tries (beyond hope) to resolve all clashes, and then finally signs everything off, clearing it for the field.

When viewed from this perspective, the workflow is crazy, but the solution is clear: The GC needs be the sole developer of all construction models, models that answer all design and constructability questions. This modeling-production self-performance work is critical to realize the true benefit from BIM.

For design-bid-build jobs, this means taking the construction documents –- that consist of drawings and specifications -- and creating a new series of models from scratch.

I absolutely do not advocate reusing any design model content, nor building on top of them with simply more detail. By strictly using CDs as the only source of information, the GC can uncover almost all documentation errors, omissions, and constructability issues that would be found later using traditional methods. These have serious monetary impacts on the project, which otherwise would go unnoticed or, more often, simply absorbed by the GC.

While it is most appropriate to do this during the pre-construction estimating and bidding phase, the reality is that estimators do not have very much time to do their work. Decent model-based estimating is difficult, because at the time of bidding the available documentation is never complete enough to develop a truly accurate price tag. There always will be missed items, or items labeled “indicative” or “preliminary” for which the GC’s design-build team is responsible to develop to completion.

Good estimators will use the design CDs and perhaps the design-intent models to generate their estimates, and then back it all up with some serious Dr. Strange-level Mystic Arts to account for hidden costs. I know a few experienced estimators who can hold a roll of CDs in their hands, mentally weigh them, and then accurately estimate a base bid, along with the inevitable change orders.

For design-build and IPD [integrated project delivery] jobs, it is my opinion that any design intent model is just too dumb to be a useful product. The design team should not actually model anything at all; below, I explain why. In fast-track delivery methods, having the architect and engineer create models is a costly duplication of effort. Even with input from subcontractors, the potential for models to become leading causes of misinformation is still there. Having the design team call these documents and models “Ready for Construction” (RFC) is just a lie that we all seem to accept.

 

Solution: Have GCs Model All the Things

It should be the GCs that wholly create the construction models, and so sideswipe the entire design intent modeling process entirely:

• First, by not reusing models from outside sources, they do not have to deal with the design team’s standards, lack thereof, or modeling oddities. Everyone has their own set of BIM modeling standards and practices, and they are all wrong, so it is always more efficient to use your own tried and true ways than to deal with someone else’s horribly broken methods.

• Second, over the long term, the GC’s BIM team will have developed a vast library of production- and constructability-quality content, which is reused in subsequent projects and ultimately shared with other project teams.

 

As for the design team, I would arm them with nothing more than a few cases of napkins and Pentel pens. Their responsibility is limited to producing hand sketches of the design. The GC’s BIM team inputs the design intent, always working in context across all disciplines. From the start, the team adds fully constructible components, framing, insulations, slab, wall, and other penetrations and openings, fabrication parts, hangers, and so on. The GC ultimately produces the documentation drawings as required; the AOR/EOR [architect/engineer of record] does the drawing QA/QC [quality assurance/checking], as well as the signing and sealing.

Regardless of project delivery method, I would extend the modeling moratorium to the trade subcontractors as well. Have the subs provide the necessary design and constructability input to simplify things, minimize complexity and installation costs, and generate submittals -- along with napkin sketches of details missed in the design intent information. But remove their modeling tasks from the job completely and have the GC’s BIM team do it all.

The GC then combines the appropriately detailed architectural models with fully constructable, coordinated, fabrication-level MEP [mechanical, electrical, plumbing] trade work from the start without any unnecessary and costly rework or delays. Add in component submittal information and the shop drawings simply fall out of the models. Have the trade subcontractor review and sign off, issue them to the AOR/EOR to approve, and the subs are then free to build with confidence.

As part of this process, the GC is in the best position to include any owner-required facilities management or asset management (FM/AM) data. Asset data is likely to change in some way between the design-intent model and the final shop drawings, such as specific manufacturer, model, and geographic location, so it makes sense for any EAM [enterprise asset management] requirement to be handled only in the most current, accurate information available – the GC’s construction models.

 

Benefits

The benefits to this approach are clear:

1. Usually, when someone bids on a project, they add multipliers to the true cost of the work. Someone may estimate 400 hours for drawing and coordination time but bid the equivalent of 800 hours. All ancillary printing costs are marked up as well, further increasing the overhead cost to the GC.

However, using this optimized process, the GC is directly paying for all production at a lower rate, can control ancillary related costs more readily, and can strike all such costs from the bids by the design team and the trades. Given the markups, this will likely more than pay for the experienced modeling team, as well as any required additional training and IT infrastructure.

2.  The GC and their trades quickly get consistent, high quality, appropriately developed and detailed models that all play under the same platform, interoperate together seamlessly, and provide the required level of detail to get things built. The owner gets their FM-related BIM requirements included as well.

3.   The GC saves a boatload of lost time stuck in post-modeling coordination, fixing design intent constructability issues, having trades lay out conflicting work in isolation, and then revising later. This eliminates a whole host of other intangibles which, directly and indirectly, impact the budget and overall construction process negatively .

4.   Most importantly, the GC’s engineering team is able to answer any question immediately, with complete confidence, to anyone in the job trailer or in the field.

 

And that’s absolutely the most valuable thing BIM can bring to the job site.

 

[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

Most years have three hundred and sixty-five days. Several CAD-related firms have chosen the same few days in April to hold their (online) user conferences:

1. Apr 19 - Aras

2. Apr 20 - Ansys

3. Apr 20 - Trimble

4. Apr 21 - Ansys, day 2

5. Apr 21 - Trimble, day 2

6. Apr 21 - Vectorworks

I plan to listen in on some of them.

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Reader D.L. pointed me to this site that promotes open source software for architecture: osarch.org. Products include:

• LibreDWG -- free C library to read DWG files

• COMPAS -- open source python framework for AEC; see figure below

• Tridify -- IFC data streaming service that supports open source

• OpenProject -- BIM project management software

• FreeCAD 3D parametric CAD, LibreCAD 2D CAD, KiCAD PB CAD

The organization held a conference last February, FOSDEM 2021 CAD Devroom, for which replay videos are available. To start with an introduction to the kinds of free software available for architects, I recommend watching fosdem.org/2021/schedule/event/bim (with Q&A).

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Kubotek3D (formerly CadKey) releases KeyCreator Pro 2021 Service Pack 1 with some pretty  interesting functions:

• Transparency shows details behind the trim (section) plane

• Locked views allow model space parts to rotate, while keeping views fixed in place

• Unalign allows dimensioned section views to move from their projected locations

• Foreground selection ignores interior and backside edges and faces

More at kubotek3d.com.

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MSC, owned by Hexagon, updates Apex Generative Design 2021.1 with guided workflows to optimize assemblies; retained volumes with LBCs [living building challenge] and material characteristics; and adapting Apex Structures to organic shaped meshes. Get details in what’s new at amendate.atlassian.net/wiki/spaces/ApexGD211H/pages/2111373317/What+s+New+in+2021.1.

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Aras releases Simulation Management for managing data of all kinds of simulation types from many vendors. Results become part of a digital thread that connects simulation to the business. I cannot, however, tell from the press release what might be new. aras.com/en/capabilities/simulation

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Nemetschek Group revenues grew 7.2% to EUR 596.9 million (approx. US$678 million) in 2020. For 2021, the company is targeting high single-digit growth, and then by 2023 growth in the mid-teens. The future looks bright: “Moving forward, the Group's internal complexity will be reduced, synergies created, and overarching solutions developed for customers from a single source.” (Managerspeak nods approvingly.) nemetschek.com

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Former Autodesk Platinum reseller Shan Chaudri launches Brixtech, Great Britain’s largest BricsCAD dealership. The online sales portal was not, at time of writing, functioning. brixtech.co.uk

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Here is a post that appeared recently on my WorldCAD Access blog:

• Guest editorial: Our Cloud Development for 3D BIM

You can subscribe to the WorldCAD Access blog’s RSS feed through Feed Burner at feeds.feedburner.com/WorldcadAccess.

 

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Letters to the Editor

Re: A Contractor’s View of BIM (part i)

That’s a great start by Matt Stachoni. I'm looking forward to the following part (or parts).

I worked as an architect, but also as a builder and developer with a lot of CAD background and project administration experience. I’d say Matt’s description of the business of doing a project is as concise and accurate as I’ve seen.

The doubling-up of work in BIM by the original designers and the GC has always bothered me, as has the increasing degree of expertise required by job superintendents. The end result is that construction today is probably more accurate, precise and coordinated than it has ever been -- but at a large overhead cost. Matt’s further thoughts will be interesting.
            - Steve Schuller

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BIM doesn't work on construction sites (but could). Our own switch to Revit did not live up to its promise.

Thanks to Ralph Grabowski at upFront.eZine for the insights.
            -Tom Morin (via Linked-In)
            Morinwood

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Matt Stachoni gives what seems to me like a fine description of some struggles for contractors. But I can’t see that any of them have to do with BIM.

They seem to me to be all about project quality and buildability. If we regard BIM as a technology, then it is hardly the technology’s fault that the design is not detailed enough, although hardware/software does constrain us somewhat.

If we regard BIM as a process, then the fact that the constructability is poor is not a failure in the digital process, but a human failure. I look forward to reading part II.

- Duncan Lithgow

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Interesting topic. Thanx for your juicy read! I really enjoyed reading Matt Stachoni’s expose.

I’ve been involved at the detailer level in BIM (IPD method). One thing I can say is I’ve never seen a benefit that came from BIM, due to construction deadlines. (Most of the projects are designed in either 2D AutoCAD or Revit.) These projects all ran at a high-pitch fervor, which causes communication to drop into a black hole, for the most part.

And when RFIs or change orders are issued, it takes forever to get responses. By that time, the job’s nearly done! I don’t need to explain what happens when stuff isn’t where it’s supposed to be due to field errors and other slight changes occur on the job. Basically, every segment of the project pretty much operates on its own, especially the contractors.

One segment completes their job and then the project lead hands off work to the next segment, who relies on the previous segment’s data to be perfect in an ever-changing world. However, nobody does their due diligence under those circumstances, and I mean nobody.

Look, it’s hard enough to get the various segments of the project to properly communicate. But when you add BIM complications into the mess, you’ve got Trouble with a capital-T, especially when they use intent-type drawings! Moreover, none of the CAD or non-CAD programs can interchange data.

My solution: Return to the stone age of pencil and paper on the board. It’s a bit more work, but the process worked much, much better than what passes for BIM today. Return to engineers managing the whole thing.
            - Chris Cadman

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I hope part ii is better. Nothing in part i that supports “he thought that BIM was generally a nice idea, but a waste of money and resources.” Hope that this will be explained in part ii. In fact part i seems to support BIM “It answers questions. That’s a hugely powerful tool to have” but is extremely light on detail.
            - Dwy Seah (via World CAD Access)

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I'm finding the discussions of BIM fascinating, even though it’s outside my normal area of mechanical design and manufacturing. I can’t help trying to imagine what manufacturing would be like if it was done the way construction is, and vice versa.

Most of my work has been at small-to-medium manufacturers of heavy equipment, so overlaying the civil/construction system onto that would look like this:

1. The engineering department releases a set of drawings to the production department that consists of an overall view of a wheel loader, with some dimensions, but lacking 90% of the information needed to build it.

2. The production department sends the drawing set to an independent engineering company, who does some of the detail design of the steel structures, and does not concern itself with the cab interior or the hydraulics system.

3. The production department sends the same set of drawings to another engineering company to design the cab, and to a third who designs the hydraulic system.

4. This stuff ^^ again, about six more times.

5. The resulting drawings are sent to four or five contractors for each area of specialization --  frame welding, hydraulics, electrical system, engine, cab, axles, etc. The lowest bidder on each is awarded the work.

6. etc.

You can see, I'm sure, where this heads. To anyone in the manufacturing world, building construction sounds like complete chaos. And BIM, which seems to me like an attempt to build a fence around the Wild West of a construction project, and force it into the kind of extremely regimented world of manufacturing, probably sounds insane to anyone who’s spent their life in a world were most of the design details are worked out on-site by the guys with the hammers and conduit benders.

It's fascinating to watch this from a safe distance. I appreciate Matt's insights, and your continued exploration of BIM.
            - Jess Davis, president
            Davis Precision Design, Inc.

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One thing which has always bothered me is that I’ve read too many articles describing all the things using BIM can accomplish. I’ve heard too many sales pitches that never mention how hard it is to find the time and person-power to enter and maintain all this data. I’d see sales presentations where upper management would be nodding their heads “Yes,” and the guys in the back of the room would be shaking their heads “No.”

Remember, this is a process. What I wanted to get across is that you can start very simply with just the parts which are the most productive. Start with design development and once that’s done, then go on to data for schedules. BIM often fails because of trying to implement too many “advantages” all at the same time. The incremental approach is the only way to succeed.
            - Dave Edwards (from his PragArchDesignTech newsletter at paagarchdesigntech.substack.com)

 

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Notable Quotable

“AWS outages -- that used to elicit extreme opprobrium a few years ago -- are now a snow day from Zoom calls.”
- Danny Crichton
techcrunch.com/2021/03/02/silicon-valleys-myths-and-realities-of-existential-risk/

 

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Comments

[dseah]

A Contractor’s View of BIM (part ii)

Interesting read. Paints an idealised workflow that has its benefits as well as problems. See ENG 2018 vid on GC-led modeling.

https://www.youtube.com/watch?v=fducJpVlTeA

Agree with the laundry list of problems but I don't think just going GC is going to solve that much. In the Mid East and Japan, big construction companies have always done the bulk of the detailed design work inhouse. In France, the contractors also use bureau d'Etudes as inhouse design and coordination resource. In would be good to get their views having done this a lot longer.

At the end of the day, pentels and sketch paper for everyone else is unrealistic... except for very simple buildings. Ironic that TutorPerini's motto is 'Building Relationships on Trust' :-)

Looking at a lot of the complaints. What is needed is better collaboration and information transparency. This means better digital tools.

Designers may lack technical nous, but Contractors are not much better, bro. They have just specialised and been at it longer and commercially incentivised.

Starting with paper CDs contradicts the real benefits made thru BIM, as problematic as it is. Analytical models (structural and energy etc) are here to stay.

Drawing duplication inefficiencies are a red herring. How is "creating a new series of models from scratch" better? The key to to filter and harness whatever info is available.

The key problem for contractors is that they have always struggled to identify problems in time in the bid documents. IPD was meant to give them the time to price the job so you don't have to rely on your 'rainmaker' estimator weighing drawings in his hand. What a mad idea!

Instead of going voodoo, contractors have been using 3d estimating tools like Destini and RiB etc to cost model the bid design using the 3d model as a basis. This is not the same as 'clean room' semi reverse engineering the design as suggested.

I also think that the savings wrt foreign standards and 'modeling oddities' is overblown. Sounds like they just haven't figured how to work Ideate et al to remap info.

Hiring experienced modelers and engineers inhouse is not as easy as portrayed. Main reason IPD fails is that your specialist subbies' biggest asset is their design staff and knowhow and they make their money from the install not the design service. Good luck with getting the expertise in house at low rates. What you will end up with is just BIM jockeys who don't have the tech knowhow... importing risk in for the GC.

Lots of complaints listed are the result of making the best of the existing BIM tools blindspots: bad 2d/3d CAD in BIM interop (Revit).. the clash detection fiasco (mainly because Revit etc can't Xref live dwg etc very well and relies on asynch declashing using Navis), ditto on lack of modeling in context, low or no LOD (mainly because Revit etc bogs down when things are 'overmodeled')etc etc

It would be better to focus on these issues instead of grand gestures. Not against GC-led modeling, but that will only go so far.