Michael O’Rourke has been a professor in the Civil Engineering Department at Rensselaer Polytechnic Institute (RPI) in Troy, NY, since 1974. He has taught over 4,000 undergraduate and graduate students. In addition, Professor O’Rouke supervised 62 students for Master of Science theses and 10 for Ph. D dissertations. From 1997 to 2017, Professor O’Rouke served as Chair of the Snow and Rain Loads Subcommittee of the American Society of Civil Engineer’s ASCE 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. He is a Former Chair of the ASCE 7 Snow and Rain Loads Subcommittee and is a Fellow of the Structural Engineering Institute (SEI). He is the nation’s foremost snow expert and is known for his extensive snow load research, authoring many articles and guides related to snow loads.
How and when did you first develop an interest in snow loads?
Like many things in life, my initial involvement with snow loads was unplanned. Prior to my arriving at Rensseleaar, a colleague of mine, Professor Leon Wang, spent a sabbatical at the United States Army Cold Regions Research and Engineering Lab and subsequently invited Wayne Tobiasson to visit Rensselaer. At that time, Wayne was the chair of the American National Standards Institute’s Snow Loads Subcommittee, ANSI A-58, Design Loads for Buildings and Other Structures. After Wayne’s lecture, we met, and I made some observations about return periods for ground snow loading. Subsequently, we corresponded, which led him to invite me to join the then ANSI A-58 Snow Loads Subcommittee, which eventually morphed into the ASCE 7 Snow and Rain Load Subcommittee.
What have been the highlights of your snow load research and developments? Do you have an interesting standout experience where you gathered a large amount of data that you analyzed, then evaluated extensively to determine the most appropriate result?
The things I’m most proud of are the two relationships for snow drift loads which have been adopted into ASCE 7. Before the mid-1980s, the drift load in ASCE 7 was a simple multiple of the so-called balanced roof snow load. I received National Science Foundation (NSF) funding to improve the then-current relation. I paid Factory Mutual for proprietary information about their observed snow drifts. Graduate students Ulrich Stiefel and Bob Speck helped analyze the data and, with a bit of engineering judgment, we established a relationship in which the drift height was a function of the upwind fetch of the drift snow source area as well as the ground snow load. More recently, a former graduate student, John Cocca, and I developed an improved relation where the drift load is a function of the winter wind speeds and the fetch and ground snow load. These relations are particularly important since snow drifts have historically accounted for roughly 75% of snow-related structural collapses.
What are some major surprises you found from your snow load research?
The Factory Mutual database contained many roof step drifts, many large right triangular snow drifts (peak height at the wall), and a few somewhat smaller non-right triangular drifts (peak height away from the wall). Our database analysis assumed that all leeward drifts had a right triangular shape while all windward drifts had a non-right triangular shape.
About 25 years later, a colleague of mine, Professor Thomas Thiis, and his graduate student, Jon Potac, measured drift formations at temporary wooden walls erected at a wind-swept location in Norway. The Norwegian outdoor experiments confirmed that all leeward roof step-type drifts are, in fact, right triangular in shape. However, they observed that, although windward drifts are initially non-right triangular, with enough wind and a driftable snow source, the non-right triangular drift can morph into a right triangular shape over time. Although the Thiis/Potac measurements disproved my assumption regarding windward drift shape, I was happy to learn the truth because it increased my knowledge of snow drift formation.
Do you have an example of “thinking outside the box,” and if so, how did it help you in your research?
About 15 years ago, I began to receive calls and emails from practitioners saying that as part of a reroofing project, the roof insulation R-value would be increased. They rightly asked about the expected increase in roof snow loads for increased roof R-values. I responded that they were correct in their thinking. Still, unfortunately, since the ASCE 7 thermal factor was based upon buildings characterized as either heat or unheated, the influence of roof R-values could not be determined from currently available roof snow measurements.
I was unhappy with my response since I felt that ASCE 7 should address this issue. Eventually thinking “outside the box,” I recalled an NSF project that estimated the size of roof ice dams, where we used a simple thermal model of the roof/snow layer to estimate the roof snow melt due to heat flow up through the roof. Using our NSF-sponsored research, Scott Russell, a long-time member of the ASCE 7 Snow and Rain Loads Subcommittee, and I developed the Ct factor for unvented roofs in ASCE 7-22, which is a function of the ground snow load and the roof insulation R-value.
Regarding the future of snow loads, what areas do you see as needing more research that will help the structural engineering community?
Since I completed my graduate education in the early 1970s, computer codes and finite element methods have revolutionized structural analysis and, to a lesser extent, structural design. In relation to snow loading, I think drift formation at roof steps and other simple geometries is reasonably well understood. However, I expect that in the future, Computational Fluid Mechanics, whereby the path of individual snow particles can be modeled, will result in an enhanced understanding of snow drift formation on geometrically complex roofs.
You have been a professor of civil engineering at Rensselaer Polytechnic Institute for over 40 years. How have you been able to mix your teaching/faculty responsibilities with your snow load research?
The academic reputation of Engineering Departments in the U.S. is based almost exclusively upon the research productivity of its faculty. At Rensselaer, we were encouraged to bring in sponsored research projects which, in turn, were used to support graduate students who did the research work under the direction and supervision of the faculty. Since the teaching load was reduced for faculty with research funding, there was little or no conflict between research and teaching responsibilities at Rensselaer.
As a professor, how would you describe your teaching style and philosophy?
I received a teaching grant from Rensselaer with the objective of improving our four structural design courses. For each course, I prepared a typed set of course notes which were provided to the students free of charge. This allowed me to cover course material rapidly and in more detail. Some of the classroom time saved was used for “in-class problems,” which I distributed near the end of each class period. Each student was required to show me a correct solution before leaving the classroom. The three main benefits were; improved learning, improved class attendance, and the opportunity to have one-on-one time with each student. Note that I could have used the extra time to present another example problem, but my strong opinion is that one learns best “by doing.” The extra “lecture” example problem would correspond to students reading a new paragraph (a simple task) while the students completing the “in-class” problems would correspond to students writing a new paragraph (a harder task).
How have you engaged your students in gaining an interest in structural engineering?
Most of my teaching at Rensselaer were structural design classes, specifically undergraduate steel design, undergraduate concrete design, graduate-level advanced steel design, and graduate-level advanced concrete design. The two prerequisites for undergraduate classes are statics and strength of materials. As such, the students have already self-selected to pursue structural engineering as a profession before taking my classes. Teaching structural design classes to structural engineering students is a real pleasure since both the instructor and the students have a genuine interest in the topic. I like to think that although I did not “lead the horse to water,” I did make the “horse’s drinking of the water” enjoyable and productive.
What are the most important attributes of being a good instructor?
In my opinion, the objective of lectures and classroom teaching is for the students to learn/understand the material. This may seem obvious to many; however, I have attended presentations consisting of two or three slides on a large number of unrelated projects without explaining any of them in-depth. The only objective, as it seemed to me, was for attendees to be impressed with the “brilliance” of the lecturer.
I like to think I follow the “students learn something” approach instead of the “audience impressed” approach. In following the “learning” approach, I typically ask myself, “what did I not understand when I was first presented with this new material?
What are the most important attributes of being a good engineer?
To my mind, the most important attributes for a good engineer are 1) a level of comfort with math, 2) a curiosity about how or why physical things work, and 3) an ability to communicate one’s ideas clearly to others.
Did you have students help you with your research, and if so, how did this teach and train them and nurture them for their future engineering endeavors?
During my career at Rensselaer, I supervised the research work of about 70 graduate students. The first thing these students typically do is read the relevant technical literature and prepare a list of items that they did not understand. Then, at the start of the new work, I would explain the items on their list and provide suggestions for “next tasks.” Some students never got past the “follow O’Rourke’s directions” phase, while the best students eventually got to a “self-directed” phase.
What advice would you give to a young person trying to make it today in engineering?
As opposed to giving career advice to a young person in engineering, I would instead mention the following opinion and observations. First, I believe there will always be a need for structural engineers. Second, during my career, I have been pleasantly surprised by the number of firm owners who enjoy the actual practice of structural engineering much more than the work associated with being the owner of a structural firm. Structural engineers will always have something to do, and most will enjoy doing it. I always enjoyed sharing this “good news” with students when the opportunity arose.
You have demonstrated a long and dedicated commitment to the structural engineering community, education, activities, and organizations such as ASCE/SEI. What were the most rewarding aspects of those services?
One of the things I enjoy the most is presenting in-person lectures on snow loads to practicing structural engineers at SEI and National Council of Structural Engineers Associations (NCSEA) events. Besides being interested in the lecture material, practicing structural engineers also ask very good questions and raise timely issues during the Q & A.
We all have mentors and people who have influenced and helped us. So, in closing, who would you like to thank and why? And do you have any parting thoughts you would like to share regarding the profession’s future?
I am grateful for all the structural engineers who have influenced me during my professional career. They include the Illinois Institute of Technology (IIT) and Northwestern University professors, my M.S. and Ph.D. thesis advisor, Dr. Richard Parmelee, and our current Department Chair, Dr. Chris Letchford. However, two individuals deserve special recognition. The first is Professor Julian Snyder of the Civil Engineering Department at my undergraduate alma mater, IIT. Besides being a great teacher, Julian would host a get-together for his students at his home. I thought this was a wonderful idea, and I have made it a practice to invite my students for a drink at the end of each semester. The second individual deserving special recognition is Professor Larry Feeser of the Civil Engineering Department at Rensselaer. Larry was hired as Department Chair in 1974, and I was his first structural engineering hire. He was tasked with converting our department from a teaching-only group to a research and teaching group. In my opinion, he was successful with this transition. As my mentor, Larry always gave me useful advice, and I always felt he had my best interest at heart.■