Professor, alumnus win research award

Felipe Cabrera

An ISU professor and former student received accolades for research that will ensure structural safety in regions with high seismic activity.

The Precast/Prestressed Concrete Institute awarded Sri Sritharan, professor of civil, construction and environmental engineering, and ISU alumnus Mohammad Ataur Rahman the 2015 Martin P. Korn Award for their research paper on seismic response of precast, posttensioned concrete using the direct displacement-based approach.

“I felt honored with this PCI award,” Rahman said. “Although I graduated from [Iowa State] a couple of years ago, I maintained a working relationship with my supervisor [Sritharan].”

Rahman, who is currently a senior structural engineer at the Ontario Ministry of Transportation Engineering Office, used his doctoral thesis as the basis for the research paper. The dissertation focused on multiple level seismic performances in terms of structural and non-structural damages of precast concrete posttensioned wall systems.

“The paper contains recommendation for the practicing engineers on how to conduct analyses and design of this structural system,” Rahman said.

It was Rahman’s dissertation that kicked off research with his supervisor, Sritharan, into how precast, prestressed concrete could be used to build structures that are more resilient to seismic activity.

“Concrete is strong in compression and weak in tension, just like a rock,” Sritharan said. “That’s why you see cracks on concrete fairly common.”

Typically, steel is put inside concrete to take the tension from the concrete, Sritharan said. Precompressing concrete in advance allows it to have more capacity for tension.

Sritharan and Rahman’s research revolved around premade, prestressed concrete pieces that can be put together on site to build structures that can withstand the stresses created by earthquakes.

“With earthquakes, what has been seen in the past, if you put structures together as pieces, they often come down as pieces as well,” Sritharan said.

Sritharan said the building must act as a structure instead of individual pieces to be more resilient against earthquakes. The inertia from the shock has to transfer from one piece to another all the way down to the foundation so it doesn’t collapse like it’s made of Jenga blocks.

The paper also looked at how to design these structures more effectively. A forced-based approach is used to design the structure based on the amount of inertia it will face. Sritharan said the issue with this approach is that the magnitude of a real-life earthquake can be more than what is assumed in the lab.

“Instead of designing for force, we design for displacement,” Sritharan said. “We want to look at a more innovative way in designing the structure and make sure the structure withstands.”

Buildings usually have to be replaced after an earthquake, but, with the designs explored in the research paper, the structures would only have to be repaired with little disruption to the buildings’ daily commercial or residential functions.

Sritharan said awards help get his research noticed, but it’s more rewarding to see structural engineers use his work as a guide in a capacity where it can help save lives.

“I think it’s always nice when somebody recognizes papers,” Sritharan said. “At the end of the day, I want to see this get built and get used by the industry rather than putting in a folder and keeping it.”