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Strength under pressure: research may lead to columns that can better withstand earthquakes

 

Dr. Riyadh Hindi knows that we live in an uncertain world. While we can attempt to identify where and when earthquakes will occur, they remain largely unpredictable. While we can build structures to withstand seismic activity, an earthquake can cause any building or bridge to fail.

“An earthquake is uncertain,” says Hindi, associate professor of civil engineering. “Chance plays a big role. You cannot predict how far you will be from the epicenter and the amount of loading the quake will place on the bridge.” An optimistic man with an easy smile, Hindi, however, embraces this uncertainty in his research. “Based on experience, we design.”

Lonnie Marvel examines concrete pillars after stress testing

Above, graduate student Lonnie Marvel examines concrete columns after testing at a structural testing facility, where they undergo pressure similar to what would occur during an earthquake. Dr. Riyadh Hindi and Marvel are experimenting with new confinement methods that will help such columns better withstand an earthquake.

He knows that it would be uneconomical and unrealistic for engineers to design structures that could withstand a catastrophic earthquake, but he does believe that it is possible to make structures safer during and after a moderate quake. Since working on his doctorate at the University of British Columbia, he has experimented with ways to improve the concrete members used in bridges and buildings so that they can better withstand the loads and deformations placed on them during an earthquake. His goal is not only to help save lives during an earthquake, but also to design structures that could be serviceable in the aftermath.

In his most recent work, which has been funded by a grant from the National Science Foundation, along with support from the university, he has developed a way to make concrete columns more ductile—more flexible so that they can withstand greater deformation, for a longer period of time, during an earthquake. “Concrete is very brittle. It will crush like chalk,” says Hindi. “But it is very strong. It can take a lot of load, but once it reaches its maximum strength, it crushes immediately. Pressure makes a concrete column expand laterally until it crushes.”

By putting steel spiral reinforcements inside concrete columns, engineers have been able to make them more ductile. The spirals provide a confinement for the concrete, so its lateral expansion is reduced and it can withstand the pressure caused by an earthquake longer. Codes and standards only allow a certain amount of steel to be used as reinforcements within columns because enough space must be left so that the concrete can flow completely and evenly around the reinforcements. Pockets or gaps in the concrete would create a much less stable column.

“So if you want to put more reinforcements to enhance the ductility,” says Hindi, “you need to overcome that problem.” In his latest research, Hindi believes he has.

He designed a new configuration that allows him to use twice the amount of steel reinforcements while keeping the same amount of spacing for adequate concrete flow. His design increases the spacing of the confining spiral without compromising the strength and ductility of the column. Thus, his design increases the amount of the confining reinforcement but retains the same spiral spacing for the concrete.

stress testing a concrete pillar

A column is tested at the University of Illinois.

After an initial small study, Hindi concluded that columns built with this new technique did outperform columns constructed with conventional single spirals. Encouraged by these results, Hindi, with the help of graduate students, constructed columns using a variety of concrete compositions, several variations on the new confinement technique, as well as columns using the traditional confinement method. They tested the columns at the University of Illinois, which has facilities to simulate the pressure that would be put on columns during an earthquake. These tests proved that the columns designed with the new technique performed very well.

When designing columns to better withstand an earthquake, engineers want to use the strongest concrete possible. With concrete, however, the stronger it is the more brittle it is and the more confinement required to make it flexible enough to withstand the pressure of an earthquake without crumbling immediately. The initial testing showed that Hindi’s new confinement technique holds a lot of promise for use in designs that call for the strongest concrete mixtures.

Hindi is hopeful that a patent will soon be issued for this design and that he and his graduate students can develop guidelines that will allow engineers in the field to apply the research to actual structures. “We need to do more theoretical work to develop design guidelines. We need to compile all the data and come up with equations that people can use to develop the code and guidelines.” Hindi believes that it is just a matter of a few years before this idea will actually be used in bridges and buildings.

Two current graduate students, Jonathan West and Lonnie Marvel, have been working with Hindi since their senior year. They became interested in this research as undergraduates, so decided to stay at Bradley and earn their master’s degrees. For their theses, they are working on testing and analyzing columns using this new method of reinforcement. Marvel’s work involves building and testing actual columns, while West is working on a theoretical analysis of the data. Two recent graduates, Benjamin Browning and Wesley Turechek, also worked on the same concept as part of their master’s research theses. Like West and Marvel, they had worked with Hindi since their senior year and decided to stay to complete their master’s.

As part of their work, these students had to get into the lab and help build the columns, securing the reinforcements and pouring the concrete. This hands-on work is an important part of the learning process, Hindi says. “They may get their hands cut working with steel, but they learn that you have to take into account the actual construction process when developing a theory,” he says. “They learn that if your design cannot be built, you have not translated theory into practice. An engineer in the field needs designs that can actually be applied to real-life situations.”

Dr. Riyadh Hindi supervises Jonathan West's master thesis

Dr. Riyadh Hindi is supervising the master’s thesis research of graduate student Jonathan West, whose work involves a theoretical analysis of data compiled during the testing of the new confinement method for concrete columns.

Coming from the University of British Columbia, a large research institution, Hindi was a little unsure when he first accepted a teaching position at Bradley. “I didn’t know what type of students I would have at Bradley, since it is a much smaller school, but I have actually been very impressed with the quality of students here. That’s what has made my career as a researcher easier—that and the support of the university.”

Hindi also says he is very pleased that many of his students have decided to pursue graduate study. “A master’s degree in the field of structural engineering is important. It will really open doors for them.” After they receive a master’s, Hindi encourages his students to go out and work, even if they think they might want to pursue a doctoral degree at some point.

“Having practical experience before you become an educator is very important in civil engineering,” says Hindi. “Students really appreciate it when you can link theory to practice, and they can see how theories are applied.” He believes that working in the field can also provide ideas for research. “You know what challenges practicing engineers.”

After earning his master’s degree, Hindi worked in his home country of Iraq for a few months. Although it wasn’t easy to leave Iraq in 1993, he eventually immigrated to Canada, where his brother had established a small engineering firm. When he first arrived in Canada, he worked for his brother’s firm and taught at a nearby college. While working on his doctorate, he also did consulting for McElhanney Engineering in Vancouver, where he gained experience designing, retrofitting, and inspecting bridges.

With his experience working for McElhanney, he knew he wanted his doctoral research to have a practical aspect. “My PhD advisor wanted me to work in a specific area, but I wanted to work on something that would help practice. I think that focusing on applied or practical research is really important. You can do work that benefits society,” says Hindi.

Hindi’s enthusiasm for practical research has influenced a number of students to work on their master’s degrees at Bradley. He continually looks for new and additional funding sources so he and his students can keep doing meaningful research. He admits that currently it is difficult for a small school such as Bradley to compete for grant money, which usually goes to more research-oriented institutions. “But we’re trying to bring up the research component of Bradley, to show them what we are capable of doing.”