Lifetime Achievement: Teaching and Learning With an HSS Expert
Peer Perspective: Carol Drucker, Principal Structural Engineer, Drucker Zajdel Structural Engineers
We spoke with Carol Drucker, principal structural engineer at Drucker Zajdel Structural Engineers, to hear about her trailblazing achievements in the industry and words of wisdom on HSS.
Q. Tell us a little bit about your professional role and some of your background experience.
A. I’ve been practicing structural engineering for over 30 years now. I started off my career designing high-seismic concrete structures in San Francisco. Fast forward to today, I’m more specialized in steel structures and live and work in Chicago.
Q. Your business is successful not only in Chicagoland but also nationwide. We’d love to hear a little bit about the story behind you opening your firm and building your business from the ground up.
A. Well, it started off in 2003. I had my own one-person shop, and Marylynn Zajdel also had a one-person shop. We used to work together at SOM in Chicago, and we decided to combine forces in an effort to get bigger projects. We started with an office in Naperville and, after continued growth, we now have our headquarters in Chicago and also an office in Milwaukee. Right now, though, we’re all working from home, but hopefully soon we will all be able to get back to the office.
Q. You mentioned how important it is for the design and construction sides to appreciate and understand each other’s challenges. Can you explain why this is beneficial and give an example of a time when it could have worked better?
A. Here’s an example that happened last week. Although we do engineer of record (EOR) work with architects, we also do connection design with steel fabricators, so our firm does both areas. I was pricing a connection job with a steel fabricator and they asked us if we thought the welded connection splices, which are complete joint penetration (CJP) welded splices, could be switched over to bolted. They asked this question before, and sometimes the answer is no because it appears to be a stability issue and a continuous shaft might be needed. This time, we looked at the drawings and said, “We don’t see any reason why the splices couldn’t be switched to bolted splices.” The reason they were asking was because there was a significant cost difference coming in from the erectors for field welded versus field bolted. I knew there was a cost difference; I just didn’t know how significant it was. I went back to our EOR design team that was getting ready to issue a set of drawings for a project and asked, “How are we showing the lateral columns splice?” Sure enough, they were CJP welded. So, I strongly suggested that the right way to go was to revise the typical welded detail to a bolted splice, gather the forces from the ETABS analysis, since we were delegating the connection design, and put the forces on the drawing so the contractor could have a better idea of how to price the job for the bolted option.
Some engineers might think, “We’ll just wait for the request for information (RFI) to come in, when the shop drawings are being developed, asking for the actual forces.” The problem with that is you’re not giving the owner the best possible price early on. They could possibly bid it as welded and end up bolted, so it’s not in the owner’s best interest. It’s also not as safe. It’s actually much safer to do it bolted. Plus, it saves on the project schedule. Also, if you wait for an RFI, it can be time-consuming and there may not be adequate time to gather the required forces in the middle of the shop drawing review. For all of these reasons, it’s best to do what’s right in the beginning. It’s these kinds of lessons you learn when you work closely with the contractors and by walking both sides of the line.
Q. Can you talk a little bit about your personal experience with HSS connections?
A. I have a lot of background with HSS connections. Besides working with HSS connections on numerous connection projects, I also had the honor of working with Dr. Don Sherman about 10 years ago. He was developing a PowerPoint presentation for AISC on HSS connection design, and as a professor at the University of Wisconsin in Madison, he had done a tremendous amount of research in the arena of HSS connections. I really enjoyed that project and helping him. Our whole office learned an incredible amount as a result.
More recently, I also worked with Dr. Jeff Packer, who is a professor at the University of Toronto and a world-leading authority on HSS connections. He, Kim Olson and I worked to improve the 2016 specifications, so there’ll be some new improvements in the next 2022 spec that’s coming out. Larry Muir, who is the chair of TG6, also had a lot of very valuable input. It was a really good collaboration exercise. I think the next spec will be well worth the effort we put into it.
Q. With HSS connections still in mind, can you give us a deeper dive into some of your favorite or most notable projects?
A. We were the EOR on the Chinatown Public Library, a beloved structure in Chicago. It’s a real architectural gem in Chinatown. As you get off the Red Line, it’s one of the very first things you see. On that project, there were round HSS for the bracing and all of it is an exposed structure, so it really showcases the round bracing that comes through the glass curtain wall. It’s an excellent use of round HSS. What’s interesting about that job is that you don’t even have to go inside. It’s all exposed from the outside. Because we were EOR, we delegated the connections, but we did have to put on the drawings what the architect wanted them to look like. For example, the HSS bracing had to be above the slab and the shear tab had to be located in a certain way, because it was all exposed, the architect had a big role in what the HSS connections looked like. It was refreshing to have that level of collaboration between the EOR, the steel fabricator and the architect.
We’re also part of a design team for a project in Chicago in which the EOR and AOR brought us in to design all the HSS connections. It’s mainly HSS, round and rectangular HSS, and it’s all exposed. We were able to coordinate with the architect in advance and say, “Hey, it’s more cost-effective to use welded rectangular than welded round and bolted connections if possible for all the HSS trusses and bracing.” So where it’s more visually hidden, we switched it to bolted rectangular, and where it’s the architectural showpiece, we kept it welded round. Then, we really dove into AWS to figure out how to optimize the round-to-round welds for all the trusses rather than just showing CJP welds, so that was a good exercise.
Q. In the very simplest terms, can you tell us what the local yielding of HSS branches means?
A. In very basic terms, local yielding of the HSS branch is due to uneven load distribution in the branch. Say you have a branch. It may be HSS connected or a plate connected to the face of a rectangular chord or support column. But because the rectangular chord has variable stiffness across the face, it’s softer in the center and becomes more rigid toward the edges at the chord sidewalls. It’s because of this variable stiffness that the load in the branch will be unevenly distributed, which can lead to tension fractures or local buckling of the branch wall since more load will be attracted to the rigid part of the chord face.
Q. Can you tell us the reason for the effective width and how does it affect the connection design?
A. Effective width very much affects the connection design. It can really haunt you when you’re doing connection designs. It’s related to the yielding of the branch. It’s the same phenomenon where the chord or the support has uneven stiffness, so there’s going to be force concentrated in certain distances, or lengths, of the branch. Say you have a 4-inch plate or a 5-inch plate welded across a 10-inch width of HSS. That 4 or 5 inches might not be effective to resist that load because of that variable stiffness across the width of the supporting element. The load will migrate to where the support is stiffer, which is what we call the effective width.
Q. Are there limit states that are overlooked in HSS connection design? Can you give us some examples?
A. Yes. I think effective width can be quite often overlooked. That’s my fear. Let’s say that you have a T-connection, basically a branch, which is the vertical part of a T-connection and the chord is the horizontal part. You might think when you’re designing that connection that the axial load can be resisted by the total length of weld around the perimeter of the branch. But because of this effective width consideration, it’s very important to look into Chapter K of the spec. There are equations in there that can be used. You have to be careful and read the entire table, taking care to use only the effective weld that you’re allowed to count on.
Q. How have you seen the steel connection industry evolve over the years? Do you have any thoughts or predictions for the future?
A. I think it’s going toward anything that makes structural steel, and even HSS within structural steel, more competitive. Any innovation that makes steel faster to erect, helps with the need for speed, and provides cost savings for the fabricator, is really where our industry will be focused.
Q. We know you’re well regarded as an excellent design instructor. Do you have any tips to share on effective communication, possibly through your presentations or in collaboration with others on a project?
A. So you would like to know how to create a very exciting presentation that captures the attention of your audience? That’s how you do it. You start just like that. To sell it, you need a hook. Engineers are really busy, so you only have about five seconds to hook them. Think of it as an action film adventure. You want to keep their interest, keep it stimulating and tell real stories. I try to “Hollywood” it as much as possible while keeping it factual and educational at the same time. That’s usually my approach. I use storytelling because I think people learn from stories.
Q. As the recipient of the AISC Lifetime Achievement Award, what are some pieces of advice or ideas you like to instill in entry-level engineers or engineers who are just starting out in the field?
A. I’d like to tell them there are actually no secrets to our profession. Everything is pretty well out there, especially nowadays when you can jump online and do some quick research. In structural steel, there are a lot of really good references. So I tell them to use all the tools available to them. There’s a lot of good information in Design Guide 24 that Dr. Jeff Packer wrote, and I know he’s updating that now, so we’re all anticipating that. And then there’s CIDECT. If you have a very unusual problem and you’re not quite sure on how to solve it, CIDECT is an excellent reference.
Q. Any other grains of knowledge that you’d like to share with our readers about steel connection design or the structural engineering industry as a whole?
A. Well, I could give some words of wisdom to young engineers. I have a couple of things that I’ve picked up through the years. I was working on a website for DZSE a couple of years ago, and I asked my brother, who’s a website developer, for some advice on website design. He said, “Carol, in order to create a great website, you have to create a terrible one first.” I think that rolls over to other ideas in structural engineering, meaning that you don’t necessarily know the right answer right off. You just have to head down a path. Get started, get the ball rolling, and eventually the right solution will become apparent. So don’t be afraid of failure and know that you’ll get to the right path eventually.
Another piece of advice I learned by working with some amazing steel fabricators throughout the years is not to jump to conclusions. If there is a problem or an issue on a project, do all the background research needed. Do the legwork to really investigate before you come to any conclusion. You might discover there’s not even a problem.
For more information on local yielding, read STI’s article Understanding Local Yielding Due To Uneven Load Distribution.