Utilizing Technology, Expertise and Communication for Better Connection Design Outcomes
Engineer’s Perspective: Jerod Hoffman, PE, Managing Director, and Eric Corwin, PE, Quality Control Engineer of Connection Design at Meyer Borgman Johnson
Our team was able to meet and interview Jerod Hoffman and Eric Corwin at Meyer Borgman Johnson to learn more about their experiences and expertise with structural engineering, new technologies and the future of the steel industry.
We chose to interview Jerod and Eric as they lead a successful team of steel connection design engineers, and can offer valuable tips and insight into ways to design steel connections and HSS more efficiently.
Q: Can you both introduce yourselves and share your career path and current role?
JH: Hello, my name is Jerod Hoffman. I began my structural engineering career in 1994, right here at the same firm I’m at today, Meyer Borgman Johnson (MBJ), based in Minneapolis. While I haven’t changed firms, I have seen a lot of change within my 28 years at MBJ. Prior to starting my career, I earned my master’s degree in steel connection design and am the co-author of Design Guide 8 (Partially Restrained Composite Connections), which I joke is probably the best design guide by AISC that gets used the least. It is an area that is more difficult for EORs to use, but it made a great master’s thesis. For the first half of my career, I primarily filled the engineer of record (EOR) role, designing all structural materials.
Midway through my career, I really became interested in leveraging opportunities within the market to focus on delegated connection design, integrated steel, using Level of Development (LOD) 400 models, design down to shop drawings — that entire process. I began my strong push for it in 2008. At the time, there were only a few firms involved in integrated steel delivery, but now it has become more mainstream.
Since then, I have focused a high percentage of my time on building our construction engineering group at MBJ, which includes connection engineering.
The other hat that I wear at MBJ is Managing Director, which could also be called co-CEO. I, along with my two counterparts, oversee management of the overall firm. We are now a 150-person firm collaborating from seven locations in the U.S. and one international office.
EC: Hello, my name is Eric Corwin, and I have about 20 years of experience in structural engineering. During the first seven years of my career, I focused on building design using a variety of materials including steel, masonry, concrete and wood. In the last 13 years, I have focused on delegated connection design with MBJ, and my current role is Senior Quality Control Engineer of Connection Design.
When I first began doing connection design with MBJ, I was the team member who developed the connections, drew them out and provided all of the calculations. I have since grown into my current role providing QC and overall direction of connection design projects as well as a lot of mentoring of younger staff. I provide final review of the connections and calculations to make sure they are safe and economical. In this role, I help our team develop into better connection engineers.
Q: Jerod, could you discuss how leveraging BIM and implementing integrated project delivery helps to ensure better steel project delivery and reduce steel connection costs and coordination efforts?
JH: I would say there is a nuanced answer to this. A couple of things: You can do this integrated steel as a single entity and lead it as EOR down to shop drawings underneath you. Or, you can just do the EOR portion and somebody else can take on the connected model portion. Then there are a lot of hybrid options to that and some can fit strategically into project contracts such as integrated project delivery (IPD) and IPD Lite. But the goal of any of these options is to remove the challenges that normally occur within the phase of handover from the EOR to the fabricator. You want to clear the hurdles using early requests for information (RFI) as well as look for more economical ways to do things in close collaboration with the EOR. A lot of it is moving things forward.
As far as reducing connection design costs, that occurs in two ways. It is finding the ways fabricators and erectors would like to do things and applying those to the project that are more practical. In some cases, it is also more cost-efficient than how EORs may have originally planned for their connections. It is often bringing the knowledge forward in the process. The other way it saves costs is it saves time. Time is a huge element to keep projects on schedule or allow more time for other activities. It also presents the possibility of bidding out the steel with more information and fewer change orders later in the process.
Q: Jerod, what are ways an EOR can set up a project early on in design to better streamline connection design, detailing and fabrication? It would be great if you could also expand on connected models.
JH: Number one, I would say EORs should put realistic loads that they put on the drawing sets if they are delegating to a connection engineer. Using realistic, slightly conservative loads will give the most economical answer and opportunity for the fabricator. Number two, do not limit the fabricator and erector too much. Give them as much flexibility with connection types as possible that will still transfer loads and provide the stability you need within those connections. And number three, do not just think about the least weight of the steel members themselves. Think about how the connections are an influence on the members they connect into. For example, if you sense a beam is going to need doubler plates, perhaps there is an opportunity to upsize the member instead of dealing with these very costly items.
As far as connected models, they are leveling the playing field by giving significantly more information than 2D drawings. In a connected model LOD 400 done correctly, it will include all of the main structural steel information needed for the connections and fabrication process. Then it solely comes down to just how fabricators and erectors apply cost to it. It is a level playing field, and the huge benefit is time. There is an opportunity to move the time frame of the detailing and connection design up further in the process and take it out of the critical path, or at least have it minimize its role relative to schedule because these items are almost always on the critical path.
Q: There is typically close coordination between engineers and detailers/fabricators. Are you able to provide a bit of insight to engineers on what would help detailers and fabricators the most in overall steel connection design?
JH: Initially, the EOR should be thinking about the most difficult and highly loaded joints as their focus area to give the most information, most attention and most collaboration. It is important to look at the load path for braced frames and lateral connections and communicate those loads properly. The second thing to consider is how the structure is going to get erected piece by piece. It will not magically get glued together! It must be lifted in place. If you think about that constructability while you are putting your drawings together, you may make different choices.
EC: At the beginning of a project, it is best to make sure everybody is on the same page. Be sure to discuss the preferences of the fabricator and specific project requirements, get RFIs off to the EOR, and provide some simple concept details too. This way, you can answer your questions early and hopefully have fewer revisions. Specifically, for HSS, I would say a good question for the fabricator is what type of bolts they plan on using.
Oftentimes, we see HSS members being used in areas that are exposed to weather and galvanized, and because of that, you want to make sure you don’t use A490 bolts because of the risk of hydrogen embrittlement. Another instance, if you are doing an overlapped K-connection truss, it is a good idea to talk to the fabricator to understand how they plan on doing the welding sequencing and where the welds are going to go. This is also an example where a concept detail will help.
Q: Could you guys describe notable HSS projects you have worked on?
EC: One notable HSS project was the Mercedes-Benz Stadium for the Atlanta Falcons. That was one of the more challenging projects we worked on.
JH: I second the Mercedes-Benz Stadium. Their retractable roof has large, movable pieces, almost all HSS. It is an eight-panel translucent retractable roof, which they call “the roof petals.” When closed, each individual roof panel overlaps the next like a pinwheel camera shutter. When opened all together, the panels extend outward like bird wings surrounding an oval-shaped opening that spans 14.5 acres. There is significant HSS usage there.
EC: Our team worked on some of the more complicated connection designs for this project, including for the eight operable roof petal trusses. We also did the connections at the intersecting ends of the main roof trusses, which were very geometrically complicated. Some of the trusses used a combination of both HSS and wide flange shape. One of the biggest challenges was the number of members framing into a single node at various angles. Using 3D models helped with our understanding of the relationships.
JH: Another notable HSS project is a significant curving canopy in a theme park in Orlando. It is a curving grid shell canopy that is all out of HSS — both round and rectangular. We were primarily the erection engineers for the project and played a smaller role in the connection engineering.
Q: Eric, could you share a few challenges you see in HSS connection design and fabrication? Are there creative ways you have overcome these challenges?
EC: HSS members are often selected because of their strength in both axes and torsional strength for girts supporting exterior walls. However, since these are usually close to the perimeter of the building, there can sometimes be significant architectural challenges with the connections due to the lack of space. For an HSS with torsion and shear and moment in both directions, a bolted end plate connection with bolts on all four sides may provide the most economical solution. But sometimes, you just don’t have the space to get the bolts on all four sides. In that case, you need to think about how much force there actually is and what other options are available. That may require more discussions with the erector and fabricator to figure out what they can do.
Q: In working with a team of engineers, what tips do you like to impart to your design team (or what lessons learned can you share) when it comes to HSS connection design? Perhaps code requirements that are more commonly overlooked?
EC: With the code requirements, you want to make sure you are considering only the effective weld properties of the connection due to the lower stiffness of local yielding of the wall away from the side walls. Some engineers also may not be aware that the 1.5 directionality factor on fillet welds should not be used for rectangular HSS’s ends loaded in tension. This is added in the AISC 360-22 and has to do with the weld only being on one side of the HSS wall, creating a local eccentricity, and the HSS weld is not restrained from rotation. There was a great article written by Kim Olson in September 2020 about this subject.
Q: The technical article provides an HSS connection design example for a typical shear connection. What would you say is the fabricator preferred WF beam to HSS column shear connection and why?
EC: I would say the fabricator preference is a single plate shear connection. This is the simplest connection for fabrication because only one plate is needed and allows for a field-bolted connection. The article provides a good example of all the checks for this connection.
Q: The other connection example provided in the article is to design an HSS-to-HSS moment connection, as can be seen in an HSS Vierendeel truss. When designing truss connections involving HSS members, what are your preferred truss members/connection types?
EC: If there are no architectural limitations, we would ideally shop weld the HSS members together as much as possible, which is like the example provided in the article. We would then use bolted end plate splices if needed for shipping or erection.
Q: At STI, we encourage that engineers check the HSS member to resist connection forces prior to bid. Do you often see a need to upsize or reinforce the HSS wall at connections? If so, what approaches do you take to resolve it?
EC: We see this occasionally, and I agree that it is a good recommendation for the EOR to check the HSS members. But as the connection engineers, we are sometimes not able to upsize the member directly. If using a slotted plate through the HSS is not applicable or sufficient for the connection type (or not preferred by the fabricator), we would reinforce the HSS by welding a thick plate to the face of the wall for the connection plate to weld to. It is not always the best thing to do, but sometimes you do not have a choice.
I would also like to note that in the AISC Code of Standard Practice 15th edition manual provides options for the EOR to either provide the design for these connections and reinforcements or provide bidding quantity information on the reinforcements. If the actual amount of reinforcement is different, the contract price or schedule shall be adjusted.
Q: How do you see the steel industry evolving as related to connection design and moving forward to streamline the overall steel delivery of a project?
JH: A lot of my ideas are really about process — how we do our work and when. First of all, it is almost always a pinch point. My hope would be, “How can we reduce critical timeline stress by doing things smarter and earlier?” Ideally, EORs have 100% of the information contained on their 2D documents, but alternatively to that, things like connected model delivery can help ensure that. My other suggestion is to bring a steel specialist on board during the design phase to give input to the EOR. They may not necessarily be doing the connected model, but they are making sure all their information is ready to go and streamlined. It’s about process.
Secondly, all EOR firms that are developing projects should be willing to hand over the LOD 300 model with a release of liability. And lastly, we hope there will be more IPD or IPD Lite types of projects. If you are familiar with IPD, it is a formal three-party contract with shared risk and shared reward. IPD Lite, as the name suggests, is less than that, but it can accomplish similar goals, such as bringing together the teams early, including the fabricator, in a big room setting where you can bounce ideas off each other before it is crunch time. As a result, you are making the decisions early as a group and implementing them for both speed and cost control. I have been a part of these collaborative, multifaceted AEC teams. It has been some of the most rewarding experiences of my career.
EC: I see a lot more computer tools and automation in the calculation. A lot more models. We are reviewing models and trying to visualize the structure. Connection design is usually under tight schedule demands to get information to the detailing people as quickly as possible so they can produce shop drawings. Using calculation tools can help to achieve these schedule demands. At MBJ, we use Mathcad for most of our calculations. Many of the projects we see are using Tekla, and we use viewers to see the model and where things are at. These help us find conflicts before we complete connections and send it to the detailers.
Q: Jerod, you have written papers and spoken at national and international conferences. What advice would you give to engineers working with connection design?
JH: Number one is load path, load path, load path. When you think about connections, you really must envision how that load goes through each part of the connection — each bolt, each weld, each plate and envision it. Draw free-body diagrams and go back to your statics. It can actually be some of the most difficult statics and load paths structural engineers can come across, even in a whole building.
Number two, if you are newer to connection design, seek out worked examples. There are great design guides by AISC and others, or seek out experienced engineers in connection engineering. Don’t just try to do it yourself. There is too much to learn. There are just tons of layers to connection design for all different types of connections.
If you just don’t feel comfortable with it, another option is to delegate. Do a good job of delegating the connection design to the fabricator. Show the loads, any specifics, preferences and requirements, and delegate it. Get it off your plate and have someone else take on the first line of responsibility for it, someone who does connection design full time in the lens of the fabricator.
And lastly, listen to the fabricators and erectors along the way and you will pick things up. Go to the job sites and fabrication shops, see how things are erected, and think about fabrication processes.
Q: Eric, you have been a mentor for a capstone course at the University of Minnesota. What advice do you have for students entering structural engineering?
EC: I would say that although it is important to know how to use the available engineering software tools, it is more important to have a general understanding of the structure and an idea of the solution before you run it. You also must make sure there is a well-defined load path for any element all the way to the foundation. If you do not understand the load path, you do not understand the structure.
Q: Any other closing thoughts you’d like to share?
JH: Working under the fabricator as a delegated connection engineer is not for the faint of heart. The speed of the work is moving as fast as possible all the time. Basically, when you get hired, it’s like “Welcome to the project — and by the way, you are late!” That is day one. There is a lot of stress and pressure along with the need to get it right every time.
But on the other end of the spectrum, you may get the opportunity to work with structures far beyond what your EOR firm might be working on or what you would experience as an EOR. You can work on incredibly significant projects and have a lot of pride in doing those. So, I believe working as a delegated connection engineer is a wonderful thing — you just have to be up for it.
EC: When we are looking at complicated connections, I use engineering judgment along with the available technical resources such as from AISC or STI to break it into simpler problems. Being able to draw a free-body diagram is often what is needed to understand the connection and the flow of forces. I also feel that my previous EOR building design experience has helped me understand complicated connections, how it relates to the overall structure and when it is best to collaborate with the EOR.
About Meyer Borgman Johnson
Meyer Borgman Johnson (MBJ) is a consulting engineering firm that offers expertise in various areas such as structural engineering, construction management, and sustainability consulting. MBJ’s goal is to help engineers and organizations tackle complex engineering challenges and achieve success through the use of innovative technologies and best practices.
Deep Dive Into HSS Shear and Moment Connection Examples
Take a look at HSS connection examples for common and less common connection types, including a wide flange beam to HSS column single plate shear connection and an HSS-to-HSS connection with shear, axial and in-plane moment.