BIM Fundamentals Seminar for Structural Engineers

Earlier this month, I attended a one-day BIM Fundamentals seminar that was put together by ZweigWhite as a pre-conference event to its annual Structural Engineers’ Building Conference and Expo, held in San Francisco on October 10 and 11. This was the first time I was attending such an event, and it provided me with an excellent opportunity to understand the BIM phenomenon from a structural engineering point of view. I also was witness to a certain amount of architect-bashing at the seminar, which led me to ponder on how BIM could foster collaboration without a corresponding change in mindsets and attitudes among the different players who need to come together to design, construct, and operate a building. Some of these observations as well as the highlights of the seminar are captured in this issue of the AECbytes "Building the Future" series.

BIM Technology for Structural Engineers

One segment of the BIM Fundamentals seminar was devoted to discussing the actual software applications that support BIM for structural engineering. Lisa Willard of SE Solutions provided a useful overview of the various solutions grouped together by functional category, as listed below:

• BIM Modeling Software for Structural Engineers: Revit Structure; Bentley Structural; Tekla Structures; Archicad; others such as AutoCAD Architecture (formerly ADT) and RAM CADStudio.
• Structural Analysis Software: ETABS/SAP; RAM Structural System/RAM Advanse; RISA; STAAD; ROBOT.

• Detailing Software: SDS/2; Tekla Structures; ProSteel.

• Collaboration Software: NavisWorks Jetstream; Interference Checking Tool in Revit Structure; Bentley Interference Manager; Tekla Structures conflict checker.

• Other: Fabrication Software; Erection Software; Maintenance Software.

What is critical in structural engineering is how data is transferred between these different categories of tools. One way is through integration and the other through interoperability, which were referred to by Willard as “direct link” and “file conversion” respectively. The direct link method has less chance for loss or change of model information, as the data is transferred directly. The following is a list of structural analysis tools showing the BIM modeling applications with which they share a direct link:

• RISA – Revit Structure
• ETABS – Revit Structure, Tekla Structures
• SAP – Tekla Structures
• RAM Structural System – Revit Structure, Bentley Structural
• STAAD – Tekla Structures, Bentley Structural
• ROBOT – Tekla Structures, Revit Structure

In contrast, in the file conversion method, a file has to be exported from one application to a neutral format, then imported from the neutral file to the second application. While this is also an effective method, the chance for model degradation is higher. The neutral file formats that are useful in the structural engineering domain include CIS/2 (see this AECbytes article, The CIS/2 Format: Another AEC Interoperability Standard), IFC (see the article, The IFC Building Model: A Look Under the Hood), and SDNF (Steel Detailing Neutral File, used for sending structural models to steel detailers). Most of the analysis tools have the ability to export CIS/2 files, which can be imported into popular modeling tools such as Bentley Structural, Tekla Structures, and Revit Structure. The following illustration from the presentation by Tom Faraone of the AISC (American Institute of Steel Construction) nicely captures the difference between the IFC and CIS/2 formats, showing how the IFC is used to horizontally integrate the different design disciplines, while the CIS/2 format that was specifically developed for the structural steel industry is used to vertically integrate the design, analysis, detailing, and fabrication processes.

Implementation of BIM at various Structural Engineering Firms

The BIM Fundamentals seminar also featured brief presentations from several structural engineering firms who had embarked upon the process of implementing BIM and who were able to share their experiences with it. One of these was by Jim Jacobi of Walter P. Moore and Associates, who had also spoken on a similar topic at the AEC Technology Strategies Conference held earlier this summer that I had written about at that time. While many of the insights he presented here were similar to his earlier presentation, he addressed staffing and training issues in a little more detail and described how many of their CAD drafters were eager to make the jump to BIM and have subsequently become designers. He emphasized the need for modelers to learn about building systems and components, so that the model can be created the way the building should be built rather than the way it needs to be drawn. Thought has also to be put into how much detail should go in the model. With regard to the technology itself, he felt that experiences with BIM such as theirs show that it does work, that the technology “has legs.” However, he cautioned that the links to analytical tools are not yet very robust, and the interoperability doesn’t work seamlessly. Nevertheless, his firm has over 75 projects in production with Revit Structure (Figure 2 shows some examples), and over 95 engineers and designers of the total firm size of 350 employees have been trained to use BIM. In addition to structural design, coordination and clash detection between models to eliminate conflicts is also becoming an important focus of the firm’s work, with NavisWorks being the key application used for this task.

We also heard about a smaller firm’s experience with BIM from Gregory P. Luth, whose firm, Gregory P. Luth and Associates, has 17 people. The firm has been using Tekla Structures for all its BIM work, the primary reason being its sophisticated detailing capabilities in addition to structural modeling and the ability to produce the 2D drawings from the model. This has made the application very popular with detailers, and it allows the firm to extend its range of services to include detailing as well, and do analysis, design, drawings, and detailing in a single integrated process. As Tekla Structures is a stand-alone structural engineering application rather than part of a multi-disciplinary suite such as Revit and Bentley, it means that the firm has to rely heavily on interoperable file formats to collaborate with the architect and other consultants. However, problems do arise with this occasionally, as the current IFC structural model is only based on what can be analyzed with RAM. This means that complex models often defy IFC translation, such as that of the USC School of Cinematic Arts project funded by George Lucas’ Lucasfilm Foundation, which is one of the firm’s current projects. The firm also experiences problems in the process of bringing different disciplinary models together for coordination and clash detection. Most often, this is carried out by storey, but the structural models that Luth’s firm creates are not always broken down by levels. Luth recounted another problem that the firm sometimes encounters with BIM—elements that are missing from the architectural models simply because the corresponding objects are missing in the BIM application that was used to create the model. An example of this in a recent project was a fireplace's flue, which wasn’t in the architectural model, resulting in coordination problems on site. Ultimately, it’s old-fashioned ingenuity that eventually fixes most problems, according to Luth’s experience, rather than technologies such as BIM.

Yet another small-firm perspective on BIM implementation came from Doug Fitzpatrick, whose firm, Fitzpatrick Engineering Group, has seven people. Their CAD experience dates back to the Intergraph era and has resulted in a fairly extensive working knowledge of MicroStation. Thus, Bentley Structural was a logical choice for their BIM implementation. The firm relies extensively on RAM Steel for the analysis and design of steel buildings, and also uses RAM for creating the building models as it is very simple, fast, and easy to use. The models are then imported into Bentley Structural, more details are added as necessary, and plan, elevations, and sections are then created by using the Drawing Extraction Manager utility. (See the review of Bentley Structural for a better understanding of how drawing extraction works.) The firm has developed a set of customized extraction rules that control how the drawings are created, what elements are displayed and how they appear. These rules are created not only for building elements but also for symbols and text. For instance, there are rules to eliminate overlapping text, so that the drawings are extracted cleanly without much additional work needed to touch them up. If the text is moved in a drawing, it remembers its location and maintains this even during subsequent updates from the RAM model. Thus, the main use of Bentley Structural in this firm at the moment is to create and maintain the link between the analytical model and the extracted drawings, so that the two remain in sync. Compared to their pre-BIM processes where the analytical model was being exported to DXF to create drawings that were not linked to the model, the BIM way has led to significant time savings, reduction of drafting errors, easier exploration of alternatives, and more time spent on decision-making than drawing production. It has also required a different thought process where notes that are normally taken for granted are now more important, a closer look for symmetry/patterns in the design, and more thorough detailing as the data will now be shared with the rest of the design team. The firm is also exploring the use of 3D PDFs to better communicate the design to others and material take-off from the model for more accurate estimating. It also eventually aims to be able to share the model with the detailer.

The final firm that shared its experience with BIM implementation was Ericksen Roed & Associates, a 60+ person structural engineering firm, which was represented at the BIM Fundamentals seminar by David Pluke. The firm is headquartered in Saint Paul, Minnesota, which has an advantage when it comes to BIM as lots of architects in the twin cities of Minneapolis and Saint Paul are very pro-BIM. The area is also home to Mortenson, which has established itself as one of the leading construction companies doing modeling for coordination and clash detection. Ericksen Roed & Associates chose Revit Structure as its BIM solution because two of its largest clients and several potential clients had committed to using Revit Architecture, and the firm wanted a solution that was highly compatible with it. The fact that Revit had an MEP application made its case stronger, along with the links that several analysis tool vendors were developing to integrate with Revit Structure. From a financial perspective, also, it made sense as the AutoCAD Revit Series that Autodesk had introduced made the licensing transition easier. It was interesting to find that factors such as the existence of a strong Revit User Group in the community and the rapid development cycle for Revit Structure also carried a lot of weight in the firm’s choice, along with Autodesk seeming genuinely interested in their input for future releases. (Needless to say, there were some excellent marketing lessons for vendors to learn in this presentation!). The firm’s implementation of Revit Structure has resulted in several benefits, including better visualization of the structure in advance, fewer RFIs and change orders, and solidification of client relationships. It is also getting new clients and becoming involved in more high profile projects. Going forward, the firm is looking for better collaboration tools, more manageable models, and the opportunity to use its BIM models in the downstream processes of detailing and fabrication. Some of the firm’s work in Revit Structure is shown in Figure 3.

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Discussion of Legal Issues and Risk

These days, no forum on BIM is considered complete without the mandatory discussion on its legal aspects, and at the BIM Fundamentals seminar, this was provided by Brian J. Donnell of the law firm, Thelen Reid Brown Raysman & Steiner. As with most of such sessions that I have attended in the past, there were a lot more questions that were raised than answers that were provided. The liability issue was at the top of the list for discussion, with the key question being who would assume liability for inputting or approving what turns out to be an error within the model. Currently, a party’s legal responsibility follows with its own set of signed or sealed drawings, but with BIM, the lines are not as clear. Another related question is that of design control, of who can change the model. Can someone other than project leaders change the model without approval? How can the quality control be protected? With the growing trend to outsource work to overseas service firms, how can you guarantee where the work is done? Other problems that can affect the accuracy and quality of the model include software glitches, bugs, or interoperability errors. Software makers typically limit liability for consequential damages and lost profits as a result of defects in their software, so the risk of using BIM falls right back on the user. Indemnification also becomes more difficult, as the blurring of who creates what and shared collaboration can make “Not at fault” more difficult to prove.

All of these liability concerns are hampering the full-fledged adoption and use of BIM technology, thereby reducing the benefits that can be harvested from it. Contracts are being developed with several disclaimers related to the model, with language such as “The User is not to rely upon the 3D Computer Model …” and “The User acknowledges that the 3D Computer Model is not a part of the Construction or Contract Documents for the Project …” This is creating a “For Reference Only” mentality with regard to BIM models, with exclusive reliance continuing to remain on the 2D documents.

Other contractual issues that arise with BIM include Standard of Care, which design professionals are legally required to exercise. If BIM technology reduces occurrence of conflicts or clashes within design documents, then will a design professional’s Standard of Care be heightened? Or will the 2D Standard of Care be less rigorous than the 3D Standard of Care? Additional issues relate to the ownership and maintenance of the model. Who ensures that the most current version of the model is being used and that old versions are destroyed? Who should safeguard the model and how? Who should archive the model to allow for a proper audit trail and subpoena response? Who pays for this and how? There are also copyright concerns. Copyright protections have been in place for architectural plans. But given that a BIM model may be a consolidated one involving the contribution of several parties, including the contractor, can the model be protected by copyright, at least in part, and if so, to whom should it belong? Who has the rights to decide which design elements within the BIM Model may be used on other projects and on what terms?

All of these are obviously more questions than anyone has the answer to at the moment. But Donnell did share some thoughts on how to overcome some of the hurdles. One of the most effective ways to break the traditional risk model is to have collaborative, integrated project delivery contracts, where the risks of using BIM are shared along with the rewards. And this is where the owner really has to take the lead and encourage cooperation across the traditional silos of design and construction. Liability will continue to remain an issue with BIM, and the best way to tackle it is to have a good design trail. The AIA is already rewriting some of its forms allowing the receiver of a BIM model to indemnify the sender against unauthorized use, modification, or disclosure. Adding disclaimers about the accuracy of the model in contracts is a really poor idea, according to Donnell, and he urged AEC professionals to embrace BIM and sell it rather than disclaiming responsibility for it. With regard to Standard of Care, he felt that it would eventually evolve to match that of what BIM can provide. He also emphasized the need to have good interoperability standards in the industry, which was especially important from a liability perspective so that different software and models could interface error-free. With regard to the allocation of copyright responsibilities and rights, it is important to have these clearly defined in the contracts. On the issue of insurance, BIM does have its complications but it is still insurable. So far, insurance companies have been slow to react to BIM, but once owners start driving the use of BIM, insurance policies will evolve in response. Essentially, he emphasized that nothing is cast in stone yet, and that lawyers are going to be playing catch-up with the technological changes in the AEC industry for a number of years.

In Conclusion: Some Observations on Collaboration

As I mentioned at the beginning of this article, this was the first time I was attending an event targeted specifically towards structural engineers, and I was quite surprised at the number of disparaging comments that were made about architects during the course of the presentations. One presenter talked about finding architects’ 3D models to be as bad as their drawings, another belittled architects as being little more than exterior designers, and someone else remarked that the things architects don’t do well get everyone in trouble. There was talk of architects being terrified of BIM and the need to get them out of the way, so that engineers could take the lead in BIM as well as lead the effort to repair the broken construction system. Architects were adjudged to be the least competent ones to be the keepers of the BIM model, but the current contracts give them this responsibility almost automatically, which is why contracts needed to be changed. The engineers were exhorted to use BIM to get in the owner’s face rather than let the architects get all the glory, do all the marketing, and show all the cool stuff.

While some of this ranting was done under the assumption that there were no architects present at the event, I did want to share it (at the risk of never being invited to attend a structural engineering conference again!) as I think it is important for architects to know that this is what engineers generally think about them. Many architects will themselves acknowledge that some of this criticism is justified. There are some architects, particularly “signature ones,” who are more obsessed with the form of the building at the expense of quality, functionality, performance, and cost efficiency. And it is natural for engineers to be resentful of the fact that all the “glory” of a design goes to the architects. As one engineer told me at this event, architects never mention the engineers when talking about their projects unless they have to.

I found it particularly ironical to encounter this resentment and antagonism at a BIM conference, when one of the key benefits of BIM is the ability to foster better collaboration between architects and engineers. Clearly, even BIM is not going to be useful here unless there is a change in attitude. Engineers need to have a better appreciation for the fact that architects are not simply designing pretty facades but designing spaces that can accommodate all of the client’s diverse needs—trying to balance a multitude of criteria including efficiency, circulation, lighting, comfort, aesthetics, etc., which is by no means an easy task. At the same time, architects need to think of engineers as equals in the design process and give them the credit that is due, along with regarding structure as an integral component of the design. With regard to the penchant some architects have for being too obsessed with the form of a building at the expense of other aspects, this is perhaps where BIM can be most useful—in allowing thorough analysis and simulation of buildings, which in turn can mandate rigorous checks for quality control. Essentially, if analysis became as important to the architect as it is to the engineer, that would lead both disciplines to be more “on the same page” with respect to building design and have a more harmonious relationship.

And in the spirit of healthy competition, I also hope that hearing themselves being described as “terrified of BIM” and “the least competent ones to be the keepers of the BIM model” will actually provide those architects who are still shying away from BIM with that extra motivating push to get out there and start using it. BIM does change the rules of the game, and as Brian J. Donnell pointed out in his presentation, nothing is cast in stone yet. Any profession can, at this point, take the lead in BIM and in providing additional value to owners. It is a race, and as with all races, the fastest one will win.

About the Author

Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and consults and writes on AEC technology. She can be reached at lachmi@aecbytes.com.