By Lorella Angelini, Angelini Consulting Services, LLC
Prof. Chris Higgins is the academic director for the TSP2 Western Bridge Preservation Partnership. He brings a wealth of knowledge and experience to TSP2, including a pragmatic approach to bridge preservation problems, striving to obtain quantified outcomes from implemented actions. Many of his research findings have become standard practice and are included into design specifications. His research on load evaluation of reinforced concrete bridges in Oregon has saved up to $500 million to Oregon’s taxpayers. I had the opportunity to speak in person with Prof. Higgins recently.
Could you introduce yourself to the readers of the blog?
I am a professor of Structural Engineering at Oregon State University in the School of Civil and Construction Engineering. I have been doing this job for more than 20 years.
Before joining Oregon State University, I taught at Clarkson University in Upstate New York. This was my first teaching job after getting my PhD. Before going back to school for the PhD, I worked for a consulting engineering firm. This experience differentiates me from most of my colleagues, who have been academics the whole time. Working in the private sector was a very valuable experience for me. I had the opportunity to work on existing structures, a practice that actually led me to bridge preservation. Existing structures in fact present much more challenges and have much more complex problems than new structures.
Do you mean the challenge of having inherent design limitations?
Right, there are a lot more criteria that come to play when working on existing structures in comparison with new structures. New design is like a blank piece of paper. You can always fill it up with whatever you like. On the other hand, when you have an existing structure, you must be able to design taking into account a lot of constraints. I like this type of challenge. It is where my interest in working on existing structures comes from.
Could you point out other significant steps in your education and career?
Before taking the PhD at Lehigh University in Pennsylvania, I did my undergraduate at Marquette University in Wisconsin and my master at University of Texas in Austin.
As I mentioned earlier, my first academic job was in New York State. Then I moved from New York to Oregon, where I live. I have lived in Oregon longer than any other place in my life.
What are the most important achievements in your career?
What I value the most are the students that I have the opportunity to mentor, particularly my graduate students. While a lot of people may not recognize that as an outcome of the academic world, the quality of our students can be regarded as the most valuable and impactful product that we produce. If you think in terms of echo and reverberation, the impact that these students will have on people and future generations is very big and lasts long.
Students are my priority. I tend to be a professor whose philosophy is “do no harm”. It is important for me to “make students better” and “take out their greatest strengths”. However, “do no harm” comes first for me.
Can you describe your practice?
I am mostly known for the work on load evaluation I did with my team when I first started at Oregon State University. In Oregon they had an issue with older, conventionally reinforced concrete bridges that were classified as deficient. At the time of their construction, designers were heavily relying on the strength from concrete thereby putting in the least amount of steel they possibly could. Detailing practices were also insufficient. The design was not poor for the standards of the time, but the state of the art is constantly evolving. It is a fact that the state of the art is constantly evolving. What the state of the art was yesterday, we can recognize as having problems today.
There was a huge need to do remediation and replacement work on the concrete bridges that had difficulties in Oregon since they all showed significant cracking. However, there was also the need to improve our ability to understand the actual condition of these bridges by using more advanced methods of analysis. We established an extensive experimental program focusing on full scale girders, with the goal to evaluate real remaining capacity. We also wanted to evaluate the effectiveness of available engineering tools to look at direct liability analysis, working on both sides of the problem, not just the resistance but also the load effect.
Taking into consideration that Oregon allows vehicles exceeding the Federal standards, we looked at what the real uncertainty of load effects would produce on these older bridges. By doing so we were able to save up to $500 million for the repair and replacement of Oregon bridges.
Could you expand upon the load effect concept?
It simply entails using a better method of analysis to calculate the capacity of bridges to carry load. If you use an old method, you get one answer. If you use a more current method, such as the modified compression theory that is adopted in Oregon, you will get a different answer. By adopting the more current method, we calculated additional load carrying capacity for the bridges in Oregon.
Is the load evaluation method also related to bridge posting?
No, it is not about posting bridges. We are actually trying to avoid posting bridges, since it creates a lot of problems and has a costly impact to the public in terms of both money and safety.
In Oregon we were the first to re-calibrate the load factors of bridges for the specific truck-loading conditions we have. So rather than using the national standard for load factors, we calibrated these factors to our unique conditions.
The load effect is not produced by a single truck but by a combination of trucks. Different states have different types of truck permits. They also have a different number of permits that they can issue, which changes the likelihood of two trucks being side by side over a bridge. In Oregon we were able to define load factors that are realistic and in line with size and number of trucks that will likely use our bridges. Previous load factors were simply too high.
Is it fair to say that the load factor is a sort of flexible indicator?
Yes, it is definitively a flexible factor. For example, when we were looking at the data, we learned that, from a probabilistic standpoint, bridges become safer during a recession.
Are there less trucks driving during a recession?
Yes. Who would have thought that safety of bridges, in terms of reliability assessment, is so strictly linked to the economy? We are actually interested in working with an economist to look at how bridge safety is impacted by the economy. It is an interesting cross-disciplinary research that broadens the way you look at bridges and their safety.
I know that Oregon DOT is also in the forefront of adopting techniques, such as strengthening, that increase the resistance of structural elements. Could you speak about it?
I would say that 90% of my work is related to existing structures, mainly bridges. My focus is on how to better evaluate these bridges, how to determine if they can carry the required loads, and how to strengthen them. We have looked at all kinds of materials and technologies for strengthening, from adding supplemental steel, both external and internal, and near surface-mounted materials, such as carbon fiber. We have also adopted titanium as a new material for strengthening.
Based on the evaluation of advantages and disadvantages for each of these technologies, we have a preference for the use of titanium. This material is metallic, high strength, and ductile. It can be bent, thus providing a good mechanical anchor to the concrete substrate, rather than just relying on bonding. Not only does the titanium provide high strength performance properties but also long-term durability.
At Oregon State University we have a unique facility that accommodates a strong floor in an environmental chamber so that we can simulate an array of conditions that actually occur with bridges. For example, we can bounce structural elements up and down applying mechanical stresses that would simulate truck traffic. We can subject the elements to environmental distress caused by freezing and thawing. We can tailor the magnitude of the stresses that we are producing mechanically with field measurements so as to create the conditions for accelerating damage.
For a lot of construction materials, we find that if we just test their strength on the laboratory floor, we get one answer. If we bounce up and down the structure made with the material, so as to have high-cycle fatigue, we get a second answer. If we just subject the material to environmental exposure, we have a third different answer. By combining fatigue with environment and then testing strength, we find, in some instances, a negative synergy. It can be said that the combined influence of fatigue with environment is more harmful than any other combination of induced stress.
This concept is especially true for concrete structures. Cracks that are usually present in concrete open under the stress induced by traffic and water can get sipped in. When the stress goes away, cracks close but some of the water gets entrapped and it is not pumped out. When this water freezes, concrete begins to deteriorate. If you use a strengthening system that only relies on the chemical bond at the surface, where freeze-thaw cycles happen at a high rate, you can likely experience the deterioration of the bond.
Does your research program entirely focus on bridge preservation?
Yes, and take into consideration that bridge preservation in the West coast also includes seismic retrofitting. If you can keep an existing bridge in service by retrofitting targeted areas so as to achieve seismic performance objectives, you can save a lot of money to DOTs and other owners.
Can you speak of your role as academic director for the TSP2 Western Bridge Preservation Partnership?
I have been academic director probably the shortest length of time between the four directors. So, I am still trying to see how I fit into this puzzle.
The Partnership shows just how common bridge preservation problems are. They are not unique to one state as they cross geo-political boundaries. For this reason, a lot of problems are better solved by the community of bridge preservation practitioners rather than by the individuals. Creating teams of practitioners, who share similar problems, and experts, who can help address those problems, is part of my responsibility as an academic director.
The Partnership has given me new ideas about problems that need to be solved. Every month during the Western Bridge Preservation Partnership conference calls, I learn about new problems and what DOT practitioners are doing to tackle them.
In summary, as a TSP2 academic director for the Western Partnership I learn about new bridge preservation challenges that DOTs are facing and I use my connections in the academic community to address those issues.
Based on your experience at Oregon State University, are civil engineering students aware of bridge preservation programs? Are they interested in these problems?
Bridge preservation is linked to existing materials, analysis and design. Most of our academic training is related to new materials, new design, latest codes, and new construction. However, Oregon State offers courses that deal with existing structures. These are elective for undergraduate as well as graduate students.
In my bridge engineering course, we deal with existing structures’ rating and evaluations but we do not have time to go into specific preservation actions.
I can say that at Oregon State we have more classes than most of the other Universities addressing existing structures, both the evaluation and the rehabilitation side. However, while the training is out there, it is not organized in a unifying program. From the outside, one would not likely be able to see it. It is available to the students in pieces but not in a holistic way.
What could TSP2 do to increase awareness of bridge preservation in the academic environment?
In 2019 I participated in all the four TSP2 Bridge Partnership Meetings. At each meeting I met only one or two academics. Definitively TSP2 could increase participation from academia in their meetings.
TSP2 is a very practitioner-applied group of people, who need to solve real problems that are faced today. On the other hand, academics tend to be more “blue sky”, that’s a generality, of course. So, bridge preservation practitioners and academics are somehow like oil and water, they do not mix easily. However, I think there is a larger amount of “oil” and “water” that can be mixed together through TSP2.
We can reach out to academic communities that are actively working locally in areas of mutual interest across the different groups. We may be able to pull more academics in, which would be beneficial to the needs of the TSP2 bridge preservation community.
I particularly recommend reaching out to academics who are involved in research since research is a skill set that can bring immediate value to TSP2.
How can TSP2 attract students, young people who can be interested in having a career in bridge preservation?
Most of my students choose to work in the building world. A good number though have taken state DOT positions or are bridge practitioners in consulting firms. These jobs are attractive to most of them.
I think that Community Colleges, which are a second academic community, could successfully engage with bridge preservation. Being applied industrial arts the focus of these colleges, their students are likely to be well suited to the needs of bridge maintenance as well as the people who would likely employ them.