Nenad Gucunski, professor and chairman, Civil and Environmental Engineering, Rutgers University

 

Professor Nedad Gucunski from Rutgers U performs novel bridge testing experiments using the large mobile shaker equipment from NHERI’s University of Austin Experimental Facility.

 

Like so many engineers, Gucunski’s interest in engineering took root in childhood. He liked to build with Legos and models. He was fascinated by buildings and enjoyed looking up famous structures in encyclopedias: the Roman Colosseum, the Taj Mahal, the Golden Gate Bridge. He read up on architects from 40’s and 50’s, including Frank Lloyd Wright. Although he excelled at math and science, drawing was not a strong suit. So, he decided to become a civil engineer.

 

He earned his bachelor’s degree in engineering in his home country of Croatia. He practiced for a year, then realized he wanted to learn more. So he set his sights on academia.

 

Gucunski’s career in the United States came about by luck, he says. First, he applied for a Fulbright Scholarship in the U.S., and to his surprise he was accepted. He earned his master’s degree at the University of Michigan. He returned home to Croatia, but in a second piece of luck (as he describes it) one of his U of M professors enlisted his help on a research project — which enabled him to return to the U.S. and earn his PhD. He is still grateful to be honored by Professor Woods at U of M.

 

Now on faculty at Rutgers University, Gucunski’s research interests are diverse. Currently, his primary interest lies in the assessment of transportation infrastructure. He examines soil structures, seismic characteristics of soil, and he conducts numerical simulations.

 

Intrigued by geotechnical engineering research at the University of Texas, Austin, he is seeking to improve current methods of characterizing soil. The SSW method has evolved into other methods, he says. The MSW method is most popular today.

 

With the 64,000 pound “T Rex” mobile shaker, about the size of a bus, researchers pound the soil and generate surface waves; sensors in the ground capture the resulting waves; researchers then analyze the velocity of the waves to infer soil profiles, Gucunski explains.

 

Early on in this work, he demonstrated how we can, by looking at different modes of wave propagation, describe soil systems. Detailing his experiments, he hopes to use his resulting data to describe soil more accurately and conduct new types of tests by ground shaking. He explains how his experimental methods can be broadly applied to both geotechical research and transportation testing.

 

He jokes that as a student, he wanted to evaluate soil systems as deeply as possible. Now he wants to evaluate systems as shallowly as possible. Shallow characterizations can evaluate pavement and concrete systems, as well as bridges, which he says has sparked the interest of transportation officials in several cities in New Jersey, his home state.   

 

Given the state of infrastructure in the United States, Gucunski’s work could be a great help. Millions of miles of roadways and hundreds of thousands of bridges are in poor condition, he reminds us. Bridges earned a C+ on the engineering report card; roads earned a D. He emphasized the need for accurate data about infrastructure conditions – to make efficient upgrades. Similarly, he says, it is important to evaluate structures using technologies that do not do destructive sampling, that do not introduce damage.

 

Gucunski discusses advances in the task, such as imaging with laser profiling and ground radar, but he says we now need to improve data collection speed and data accuracy — and accurate data analysis.

 

He lists numerous examples illustrating why bridge structure evaluations, depending on construction type, present particular problems. Ultimately, he says, we want to extend the life of a bridge at minimal cost.

 

One of Gucunski’s most recent projects is the NSF Eager project, Informing Infrastructure Decisions through Large-Amplitude Forced Vibration Testing. Using the large mobile shaker fleet based at UT Austin NHERI facility, he wants to assess structure soundness.

 

He’s convinced that we can get key information for making infrastructure decisions by using large amplitude force vibration. The five large shakers from the UT NHERI facility are used primarily for geotechnical applications. Researchers use them to do modulus profiling and to characterize structures like embankments, levees and dams.  

 

By using the shakers to assess structures, Gucunski says, we can understand and predict how they will perform under extreme events, like earthquake loading. He hopes to establish the viability of these machines for use in evaluating structures and their performance under hazard loads.

 

He describes his processes of evaluating existing structures with the T Rex shaker, as well as his parametric studies to validate the work, and his findings. He is thankful to the New Jersey Department of Transportation, which was brave enough to give him access to a bridge to shake. He shook the ground in multiple directions and at multiple load levels to see how the bridge would respond.

 

He used T Rex was in a range of frequency sweeps, from 80 Hz down to 1 Hz. He and his team captured the response of the bridge and surrounding ground using geophones and accelerometers to determine the interaction between the soil and the structure sitting on it.

 

By comparing his parametric studies with the data gathered in the field with the T Rex shaker, his goal is an efficient way to assess structures like bridges. Looking to the future, Gucunski hopes to provide practical data and methodologies to researchers and infrastructure managers.