Key Insights From a Global Expert on Blind Structural Fasteners, Welding and Beyond
Peer Perspective: Bob Shaw, founder and president of Steel Structures Technology Center in Howell, Michigan
We spoke with Bob Shaw, founder and president of Steel Structures Technology Center, which focuses on technical education and consulting services related to the fabrication, erection, inspection and quality of steel-framed structures. A distinguished recipient of the AISC Special Achievement Award, we asked Bob about his experience and widely sought expertise in the world of bolting and, more specifically, blind structural fasteners.
Q: You are prominent in the bolting world and serve on several code committees. Can you tell us a little bit about your role in providing that technical education to professionals around the fabrication, erection, inspection and quality of steel frame structures?
A: I’ve been around steel construction since 1973. I actually started working for a steel fabricator as a summer job during college and went to work for them for another six years after I graduated. When I went to work for AISC, I did a lot of training seminars and presentations as a Regional Engineer and then as the Associate Director of Education. The teaching aspect was part of my profession for about 10 years with AISC. I formed my own company in 1990 to continue teaching. When I started teaching seminars to professionals and explaining things in codes and standards, I found that I could benefit from going to the code committee meetings. This gave me a much deeper dive into the standards and also gave me the opportunity to suggest changes and improvements.
Q: Can you explain some techniques or methods for bolting to HSS members that could increase the efficiency of the connection and what type of applications this might be used in?
A: One inefficiency of connections to tubular members can be from the lesser amount of rigidity of the tubular walls, so what helps is stiffening up those walls. I’d love to see more innovation to try to address that particular subject, and I can see that being done through mechanization or through the application of robotics. I can envision a long, stiff arm that’s inserted down the length of the tube, which would have a vision system to locate and weld an internal stiffener, and locate and weld a nut keeper. A person’s arm couldn’t do that, but a machine can. If somebody created that equipment, it could make a big difference in how we approach tubular connections because we wouldn’t be so concerned about stiffening. It would be cleaner, and we wouldn’t have to use exterior diaphragms or rings to stiffen. It could result in both architectural and structural improvements.
Q: Can you describe some challenges associated with using bolts with HSS members? And with that, do you have any suggestions for preventing or overcoming those issues?
A: When you have a hollow structural section, you need something on the inside and the outside, or you use through bolts. One of the challenges with using bolts in HSS is the member tends to have thinner walls with limitations on the bolt capacity that can be developed. The use of a nut keeper system certainly has overcome the problem of developing bolt capacity and being very efficient, but then again, the placement of a nut keeper inside an HSS is still a challenge.
I think people look at HSS for its architectural cleanliness and smooth lines, and that’s actually a challenge for the use of HSS. People aren’t taking advantage of HSS for structural purposes, accepting that you can have very efficient details that may not look as nice and clean. Perhaps the clean, smooth line of an HSS is prompting people to come up with very difficult connections because they want the connections to have clean, smooth lines. That’s why we spend so much time talking about hidden connections. In a lot of steel buildings, you don’t have to worry about those hidden connections. It’s efficient to use HSS, especially with larger sizes and wall thicknesses. I think trying to make everything internal and hiding those connections is putting unnecessary obstacles and limitations in the way of HSS.
Q: What are the top three things you wish everyone in your field knew about bolting to or welding to HSS?
A: Well, I split it into three for bolting and three for welding.
1. You can bolt the HSS. I think there are some people who don’t think you can bolt the HSS or connect HSS to HSS using bolts.
2. You really need to plan ahead when bolting to HSS, and you have to study to choose the right kind of product you’re going to use to make those connections.
3. Bolting really speeds up the field work and reduces issues like tolerances and distortion that can be caused by trying to weld a splice or connection to the side of the HSS. So, I would encourage people to consider bolting, as long as they plan ahead.
1. The first thing they should be thinking about is using partial joint penetration groove welds, PJPs, instead of complete joint penetration groove welds. Sometimes people say, “OK, I’m going to have them weld the full thickness,” and that becomes very complicated with HSS to HSS because now you may need ring backing or specially qualified welders or procedures and so forth.
2. There’s going to be some distortion and some shrinkage and perhaps warpage, and those considerations need to be made also when people are welding so that they can plan for that.
3. Welding actually is probably the most effective when people are indeed interested in achieving a very nice, smooth architectural structure.
Q: What are your thoughts on using snug tight through-bolts in connections to HSS?
A: One issue is getting it tight enough, and if you don’t, it acts like a pin and rolls around. The issue there is that you won’t get the stiffness in the joint you’re looking for. And if you tighten it too much, then you start to bend the walls of the tube, which creates another set of problems. So, through bolts don’t seem to be a good solution in my view. You also have to worry about misalignment from one side of the tube to the other and what effect that could have on the performance of the joint.
Q: Let’s talk specifically about the blind structural fasteners or one-sided bolts. These are designed for installation without access to the other side of the joint. In what application is this one preferred?
A: They’re quick and easy, and it is indeed one-sided for the person is who’s making the connection. The downside is the reduced capacity of the bolt. That has to be considered and perhaps limits the load that’s applied because of the wall thickness. If we’re looking for that speed and efficiency in construction, time is money and labor is money. People might want to actually think about using thicker wall HSS and spending more money on the material to make the cost of the connection a lot less or a lot more efficient.
Q: Are there any other grains of knowledge you’d like to share with our readers about this topic or the steel industry as a whole as we look to the future?
A: Thanks for the opportunity on that because when it comes to preaching about HSS or blind structural fasteners, I have nothing to add. However, I would like to encourage that people do continue to look for innovations in fabrication and erection and products that can be used, connection types and so forth for HSS.
Second, I would like to encourage people to get involved in the standards process, to get involved in AISC, RCSC (Research Council on Structural Connections) for bolting, AWS for welding. We have people who have been around a long time who have a lot of knowledge we can share, but we also need people we can mentor to pass the information on, because we won’t be sitting in these meetings forever. We need people to get involved, especially people from the fabrication and erection side so we can see or listen to their ideas. We can not only pass on information to them, but they can pass information on to us. And when you all work together that way, that helps. We’ll make them better fabricators and better engineers and better erectors, because they’ll learn from understanding the code better, just like I did 30 years ago. Then, they can start to share their knowledge, and that improves the code.
I’d also like to encourage them to think globally. In our industry, people need to think globally to see what’s being done around the world for best practices and new innovative products, and to use the best of the best. There are international standards. I’m in charge of one now, and we have people from the U.S. and Canada, several European countries, Japan, China, New Zealand, Australia and others. It’s amazing the exchange of information that takes place in those meetings. We’re actually trying to develop a best practice and bring that back to each of our countries. That’s a very rewarding experience, assuming that the standard gets finished and published.
To learn more, read STI’s article.