Abdul-Rahman Salkini ’07 Tests Strength of Reinforced Concrete Structures

This year, civil engineering major Abdul-Rahman Salkini ’07 (Aleppo, Syria) is continuing a groundbreaking study he began this past summer on testing externally strengthened two-way reinforced concrete slabs.

Salkini collaborated on the summer project with Stephen Kurtz, assistant professor of civil and environmental engineering, through Lafayette’s distinctive EXCEL Scholars program, in which students conduct research with faculty while earning a stipend. The program has helped to make Lafayette a national leader in undergraduate research. Many of the more than 160 students who participate each year share their work through articles in academic journals and/or conference presentations.

The researchers focused on a technique for retrofitting existing reinforced concrete structures, which involves bonding sheets of carbon fiber to the exterior of reinforced concrete beams. Salkini and Kurtz then measured the states of stress between the carbon fiber and a reinforced concrete bending member, while under load. The stress analysis allows engineers to predict and prevent failure.

“The structural members were two-way slabs that weighed 1,600 pounds each,” explains Kurtz. “A two-way slab is a bending member that is supported on all four edges so that it spans in two directions, deforming like a bowl, as opposed to a beam which is a one-way bending member with one span between the two supports. The slabs were tested with a uniform pressure that increased slowly, over the course of hours until failure occurred. A total of 16 tests were conducted to failure.”

Salkini and Kurtz applied the pressure using water-filled bladders that were placed between the test slab and floor and were connected to the Acopian Engineering Center’s cold water supply. While slab failures required, at most, 10 pounds per square inch of pressure, most commercial buildings have water pressure that is at least 50 pounds per square inch. In other words, a building’s tap water pressure is five times greater than the pressure needed to fail the building’s floor.

“A small pressure multiplied by a large area leads to a considerable force,” says Kurtz. “Consider that 10 pounds per square inch multiplied by an 85 inch by 85 inch slab is equal to more than 72,000 pounds of force. This large force was resisted by holding the slabs down to the floor with a structural steel frame connected with 12 two-inch diameter bolts.”

Salkini points out that their research was the first to test two-way slabs, which is a more realistic application than testing beams.

“Extensive analytical and empirical research has been carried out to develop a technique that allows us to predict the failure stresses and mechanism,” he says. “Yet, the analytical research has been proven to be unreliable. Also, all the research carried out has been on one-way beams. Another problem is that up to this point, none of the researchers were able to physically measure the interfacial stresses due to the lack of appropriate technology. This meant they derived the failure stresses indirectly, which is not accurate. Our research tried to tackle these two problems.”

Salkini jumped at the chance to work with Kurtz, knowing that the opportunity would allow him to dig deeper into the field of structural engineering. Several peer-reviewed journals have expressed interest in the results.

“I knew I wanted to do EXCEL to experience doing research because I felt that would prepare me better for graduate school while making me a more competitive applicant,” he says. “I knew for a fact that working with Kurtz would mean that he would push me to the maximum and that I would not be wasting my time or bored at any point because everyone knows he is a very demanding professor. That turned out to be very true.”

Kurtz was impressed with Salkini’s abilities, noting that the biggest adjustment for his student was the physical labor and construction skills necessary to conduct large-scale structural testing. Salkini had to determine logistics such as moving and storing the slabs and working with them safely.

“Abdul-Rahman is a top-notch student,” says Kurtz. “[He] poured a tremendous quantity of concrete and performed a great deal of welding, fabricating, and rigging, not to mention testing.”

Kurtz believes the EXCEL program is a necessary stepping-stone for honors thesis research in the department. He is serving as Salkini’s thesis adviser for a project in the same field this year.

“The EXCEL program is essential for preparing students for the senior thesis; they go hand-in-hand,” he says. “Without EXCEL, it would be very difficult for students to be adequately prepared for a senior thesis. The senior thesis is a special part of our program. Nationally, they are quite rare, particularly in engineering.”

Salkini echoes Kurtz’s feelings about the EXCEL program, noting that it helped him define his goals for his honors thesis and taught him the skills to carry it out.

“I am trying to build a machine that tests specimens in three axes to develop a failure surface,” he explains. “This would be the optimal way of predicting the failure stresses. My thesis would have been impossible to even attempt if it was not for my EXCEL experience. Lafayette provides a truly unique experience to undergraduate students of doing research working closely with a professor. While having the independence necessary in doing research, the close environment at Lafayette means the professor is always present in the research, never leaving the student at a complete loss. Even in places that provide the research opportunities at this level, I highly doubt [students] get to work as closely with their professors as we do. The equipment I was dealing with, undergraduate students in other institutions would not be allowed to touch.”

Salkini and Kurtz formed a special student-mentor bond during their long hours of work together preparing the slabs for testing. Salkini believes Lafayette’s research opportunities foster close student-faculty relationships.

“That experience was by far one of my best and most enriching at Lafayette,” says Salkini. “I learned issues about structural engineering my peers had never even heard of, while having the chance of applying some of my previous knowledge. More importantly, I learned about various issues just by being with Kurtz. Our research was not typical in the sense that it involved mostly physical work like mixing concrete, painting, and applying epoxy. Each of these tasks required us working together for hours upon hours doing the same repetitive task. Structural engineering was only one of the issues we discussed; we happen to have very similar interests outside engineering. We talked extensively about world politics, especially in places like the Middle East, which is where I am from. We both have a passion for history, so we discussed world history from Latin America all the way to ancient China. I got to learn a lot about Catholicism and Christianity and teach him more about Islam through our discussions about religion. Kurtz is an extremely well rounded and educated engineering professor, and that is what I aim to be at some point.”

Salkini is a member of International Students Association and Delta Upsilon fraternity. He also volunteers with the Boys and Girls Club of Easton through the Landis Community Outreach Center.

Kurtz has mentored numerous students in individual and group research since joining the faculty in 2002, including civil engineering graduates David Donovan ’03, Jeremy Lucas ’03, and Fernando Luna ’03. He is the adviser for Lafayette’s Steel Bridge Team and received the American Society of Civil Engineers’ ExCEEd (Excellence in Civil Engineering Education) New Faculty Excellence in Teaching Award in 2005.

He also led an effort that resulted in a $243,526 National Science Foundation grant to establish a engineering laboratory that has opened up new learning opportunities in several areas for civil and environmental engineering, mechanical engineering, and mathematics students. He earned his Ph.D., M.S., and B.S. from Rutgers University.

As a national leader in undergraduate research, Lafayette sends one of the largest contingents to the National Conference on Undergraduate Research each year. Forty students were accepted to present their research at this year’s conference.