Old School Meets New School: Insights From the Creators of the Roof Bay and Floor Bay Analysis Tools

We talked with Jim Fisher, Ph.D., P.E., vice president emeritus and consulting structural engineer, and Mark Denavit, Ph.D., P.E., associate professor at the University of Tennessee, about their perspectives on how structural engineering has changed over the years and the future of engineering students, design tools and more.

Then and Now: How Engineering Has Changed Over the Years

Jim and Mark are friends and colleagues, having worked together on aspects of the Steel Joist Institute’s (SJI) Roof Bay and Floor Bay Analysis Tools. Jim has been an engineer since the ’60s. He is currently retired but still busy doing consulting work for SJI and other code and specification committees. Mark, on the other hand, has been an engineer since the mid-2000s and has been teaching for the majority of his career. Speaking with them together, it’s interesting to see how their different generations and backgrounds in engineering affect their perspectives on how the field has changed over the years. 

Jim is proud of the old-school fundamentals. He puts a strong emphasis on the ability of engineers to master engineering principles, understand the math involved and, above all, think critically. “[In the last 20 years], I think engineering has changed,” says Jim. “The principles haven’t changed, but there’s more emphasis on speed and getting things done quickly. That’s all good, but I think there’s less thought going into many designs than there used to be. I am concerned that a lot of the young engineers don’t think enough about their designs. They just substitute numbers into all these wonderful tools we have.”  

Jim compares engineering to when he was starting out versus engineering today. “When I started, engineers did their own drawings. Then we went through a whole period of time where there were draftsmen or draftswomen who did the drawings, and the engineers just did calculations,” Jim says. “Now we’re back to the engineers doing drawings again because of AutoCAD, and I think that’s a good thing. The engineer gets a better perspective of how things are put together, and that’s important.” 

Mark, while appreciating the need for the fundamentals, is a bit more optimistic about how things have progressed and the use of tools while still acknowledging the need to properly understand what they do. “Today, there are a lot more design tools to do the engineering work,” says Mark. “In part, it’s because the specifications are getting more complicated or allow more complicated things to get done. Engineers have to really understand the tools they use.”

Developing Judgment to Properly Use Design Tools

It’s no debate that the emergence and development of engineering design tools have changed the way engineering is practiced. With various subscription softwares and online tools, engineers have many more resources at their disposal to draft and test designs. But are these tools always a good thing? “There is a lot of good that comes from all these tools,” says Jim. “But there’s a bit of a lack of understanding by engineers on what all the tools are doing.” He continued by explaining how young engineers need to develop judgment when it comes to design and how one must learn from their own judgment errors. 

“Engineer Hardy Cross said once, ‘First design the structure using your best judgment, then analyze the structure. And if your numbers do not support your design, then reevaluate your numbers. If the numbers still do not support your design, then evaluate where your judgment may be in error.’ I think that is so good. Most people think that structural engineering is a black-and-white thing. It’s not. It’s art,” says Jim.

Mark agreed with much of Jim’s sentiment, saying that it’s easy to secede your own judgment to these tools. But if an engineer understands their tools and their limitations, these tools can be immensely helpful. “Design tools can be used as virtual labs to evaluate hypotheses that you might have,” says Mark. “That’s one way to build judgment beyond just simply making mistakes. They can see, ‘OK, if I change this, what happens? Could I have predicted that? If I could have predicted that, great. If not, why is it different from my expectations?’ It’s all about the engineers retaining the responsibility for their designs and not trying to outsource that judgment to the design tools. Then tools are great because they speed things up and make more things possible.”

New Tools for a New Age of Design

Both Jim and Mark have worked on tools to assist in designing: SJI’s Roof Bay Analysis Tool with ponding analysis and the Floor Bay Analysis Tool with vibration

The Roof Bay Analysis Tool

The Roof Bay Analysis Tool assists with selecting optimal bay sizes and framing options. It provides several input options to allow for customization based on project criteria, designer preferences, owner and code requirements, and different ponding analyses.

A structural engineer of record (SER) will find that the Roof Bay Analysis Tool has many useful features and benefits. It allows engineers to input cost information and figure cost per square foot. It allows for both ASD and LRFD design procedures. It allows an SER to quickly compare joist solutions to those with wide flange shapes or channels. And it’s especially good for conducting preliminary design. 

“The preliminary design is very important,” says Jim, “because, as one of my colleagues used to say, if you make a wrong decision in designing a structure off the bat, you’re going to be faced with all the additional calculations trying to justify that poor decision you started with.”

The Roof Bay Analysis tool also has ponding capabilities, which Mark was the leading force behind.

“Not to toot my horn too much,” says Mark, “but the ponding stuff is a unique feature and capability, and the Roof Bay Analysis Tool makes it so easy. The tool broke ground on a particular method that was a precursor for what is in the latest national standard for loads.”

The ponding analysis is most beneficial when run in a preliminary analysis when designing a bay or roof where ponding is going to control. Since an SER would assume roof drains are blocked, the ponding analysis can help identify if the secondary drain is placed well or needs to be resized or relocated.

“Overall, the Roof Bay Analysis Tool has a very good balance,” says Mark. “A balance of providing information versus clarity. It provides enough information that you can really track the calculations without providing so much information that it’s difficult to visually see what’s going on and quickly interpret the data.”

The Floor Bay Analysis Tool

Like the Roof Bay Analysis Tool, the Floor Bay Analysis Tool assists with selecting optimal bay sizes and framing options. It provides several input options and allows for customization based on project criteria, designer preferences, and owner and code requirements.

The Floor Bay Analysis Tool has many features that are beneficial for SERs as it pertains to joists, joist girders and metal decks. It allows engineers to input cost information to optimize builds. It allows them to quickly compare joist solutions. But a powerful feature is the vibration analysis.

“The Floor Bay Analysis Tool will check whether or not there’s going to be a floor vibration problem that will be disturbing to the occupants,” says Jim. “For example, walking in office buildings. You might feel that the structure’s falling down because you can feel it vibrating.”

Educating the Next Generation of Engineers

When it comes to educating future engineers, both Jim and Mark have some invaluable insights for students looking to join the field.

“Have the mental tools to be able to ask a question, be able to think through a problem and break it down into its component pieces,” says Mark.

“It’s not bad to ask for guidance,” says Jim. “There are a lot of people who don’t want to ask questions, but that’s how you develop judgment. I once gave a talk on judgment and the young people asked, ‘How do I get judgment?’ I replied, ‘judgment comes from experience and from examining the poor judgment or mistakes of others and of oneself. Successful engineers of the past are often our best teachers of judgment. If you make a judgment error, or a calculation error you are unlikely to make the same error again.’”  

To learn more about the Roof Bay Analysis Tool, the Floor Bay Analysis Tool and other design tools from SJI, visit our resource page.