With little more than a smartphone app and a rope, Maria Gibbs, S.M.ASCE, a Ph.D. student at the University of Notre Dame, was able to do something that normally requires a team of structural engineers and a truckload of fancy, expensive equipment. Through her research work as a National Science Foundation Graduate Research Fellow, she was able to create a simple dynamic testing procedure that she terms a Citizens Sensing Project, which would capture the dynamic characteristics of suspension footbridges.
“We know from experience that suspension bridges, particularly slender bridges with low structural stiffness and mass, suffer from a unique vulnerability to wind,” explained Gibbs, whose research on bridge aeroelasticity was so closely tied to her volunteer work with Bridges to Prosperity (B2P) that she spent a year working for them as operations and research coordinator.
“So my job,” she noted, “was to erase that uncertainty and develop a tool that is going to predict how these structures will respond to the wind so that we can design and build these bridges safely, and to last a long time.
“The first step is capturing the dynamics of the structures using a portable, low-cost testing procedure which is easily deployable to rural footbridges all over the world – i.e. a smart phone app and a rope – then using this data, along with information about wind-induced buffeting and flutter, to develop a tool which predicts the behavior of suspension footbridges under wind loads.”
In partnership with a team of researchers from Bauhaus University, Weimar, who developed the smartphone app, they tested this citizen sensing procedure on a series of 14 footbridges in rural communities in Nicaragua, El Salvador and Rwanda, validating measurements from four footbridges against industry standard testing equipment.
“This is important because B2P is pushing the span limit of these bridges for communities that are coping with extreme isolation,” states Gibbs, who also serves on the B2P Board of Directors. “Bridges with longer spans are even more susceptible to this [wind-induced] phenomenon. So [B2P has] encountered situations where we just can’t build a bridge because the span would be too long, or we are uncertain as to how it is going to react in the wind.
“There is still a ton of work to be done [in developing this tool], but what we have done so far is step one: figuring out how to test the dynamics of these bridges using a cool innovative approach. Because what B2P is essentially trying to do is answer the question: how we can support communities on a scale commensurate with the need. To do that, we need robust bridge designs that are built to last in some of the most challenging environments in the world.”
Gibbs’ desire to become a civil engineer began back in the summer of 2005, when Gibbs traveled to El Salvador and became friends with Gloria Sandoval and her sister Reina, who were living at Natalia de Siman, an orphanage for girls. Since then, Gibbs has returned there every summer where she has volunteered to do everything from create a library to teach math at the orphanage.
“My natural reaction,” says Gibbs, who decided to enroll in the civil and environmental engineering program at Duke University, “was to try and do something to help. So I started Cards for Las Niñas, an organization that sold greeting cards to raise money for the orphanage to buy clothes, medicine, and school supplies. I couldn’t help but feel discouraged by the transience of the benefit the money provided and I realized that by studying engineering, I could have a more profound and sustainable impact.”
During a conversation with her friend Gloria Sandoval, who graduated from the orphanage and became a school teacher in a remote Salvadoran village, she came across another stark realization; that students living in the area had to wade or swim across a dangerous river to get to school because there was no bridge.
“That was infuriating to me,” she recalled, “Kids in El Salvador risked their lives getting to school when there seemed to be a really simple solution: build a footbridge. So, I went back to Duke and started this organization, Duke Engineers for International Development. By pure chance, while doing an assessment trip for a footbridge in El Salvador, I ran into the country’s B2P director, and so started my collaboration and involvement with them.”
Although she does not yet know what her future holds when she graduates in 2017, Gibbs believes that people deserve the opportunity to be healthy, be educated and support themselves and their families. “That is what drives my work and will continue my work,” she says.
Gibbs concludes, “It was not until I was hauling rocks next to a farmer in El Salvador, who told me that the footbridge that we were working on was going to allow him to get his crops to market or when I was bending rebar with a couple of kids in Nicaragua and they were so excited because that footbridge [we were building] would mean they no longer risked swimming a river to get to school, that I realized as civil engineers, we have the good fortune to work on projects that touch people’s lives every day.”