Building better bridges

Building better bridges

The ISIS Canada Research Network provides civil engineers with smarter ways to build, repair and monitor structures
November 10, 2009
ISIS research engineer Chad Glowak (at left),
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ISIS research engineer Chad Glowak (at left), ISIS president Aftab Mufti (centre) and resource centre manager Evangeline Murison.
Tamara Nathaniel

(Reprinted with permission from ResearchLife, Summer 2009 issue, University of Manitoba, umanitoba.ca/research)

It was 1952 when Aftab Mufti, a 12-year-old boy living in Karachi, Pakistan, began building bridges. His mother planted a vegetable garden that summer and to help her water it Aftab and his older brother Mehtab cut a trench connecting their backyard pond to the plot. But the gully often ran dry so the boys took shifts sloshing water down it with their only bucket.

The idle boy, bored, gathered nearby stones, sticks and mud and built a bridge that his brother then tried to ruin with floods. Back and forth they went, days on end, building and destroying bridges. Aftab studied his design faults and continually improved them. Years later he acted on his father’s encouragement and pursued a career in civil engineering. He is now the president of ISIS Canada, a group of 150 researchers from 15 Canadian universities responsible for paradigm shifts in civil engineering research.

Meanwhile in Switzerland, when Mufti was playing in his backyard, Urs Meier was spending his summers with his grandma who went to elementary school with the famous structural engineer Othmar Ammann, and instead of reading bedtime stories to Meier she would tell him tales of Ammann, showing him pictures of the Ammann’s bridges. Fascinated by this world, he decided to study at the same university Ammann did — Polytechnikum in Zurich. Years later, after studying in American laboratories, he returned home in 1988 with an idea that got Mufti’s attention: using new materials called fiber reinforced polymers (FRPs), he wanted to build a bridge across the Strait of Gibraltar using only a single span 8.4 kilometers in length. (Conventional methods limit a bridge span to 4 kilometers.)

“That really put so much interest in our thinking that we went to talk with him. He was on the right track,” Mufti said. “You see, he was saying these new materials would last for a long time, inside and outside of concrete. So we were very interested. First of all it was fascinating, but we wanted to know how he was using this material and how Canada could move into this new way of doing things. And that was the start of ISIS.”

ISIS — the Intelligent Sensing for Innovative Structures Canada Research Network — has always been headquartered at the University of Manitoba, and since 2000 Mufti has sat at its helm. Upon returning from Zurich, Mufti asked the Canadian Society for Civil Engineering to form a technical committee on advanced composite materials for use in bridges and structures. They agreed and appointed him as its chair. The committee matured and in 1995 it became ISIS Canada Research Network, joining the ranks of the federally funded Networks of Centres of Excellence. Such centres are funded a maximum of 14 years, and this year ISIS reached its expiration date. So, what has it accomplished, and how will it take to the future?

Twenty years ago no Canadian studied the use of FRPs for civil structures. Today, more than 200 researchers work in this field. What is now ISIS has been involved with at least 150 projects using these materials, the first being Beddington Bridge in Calgary in 1993, and it still performs beautifully.

“I guess ten years ago any project in Canada that used FRP would have the ISIS logo attached to it,” said Doug Thomson, an electrical and computer engineer at the University of Manitoba and a future co-chair of the ISIS Canada resource centre. “And now, I suppose as a measure of its impact, that’s not true. The vast majority of things go on without any ISIS involvement, which means that the technology has moved from being a research kind of proof-of-principle thing to going out there and being part of the normal toolbox for people to use in structures.”

Indeed, over the years ISIS has developed eight design manuals and actively worked on national code committees. One of the national codes (S6-06) deals with the work of Dagmar Svecova, an associate professor of civil engineering at the University of Manitoba and the other future co-chair of ISIS. She studies ways to rehabilitate timber bridges, which Manitoba has hundreds of, and now people from across Canada call her to learn more.

“What we are promoting right now is you take a router and you make a groove in the tensile side of the timbers — the stringers — and you put epoxy in it then FRP bars and voila. It can even be done while there is still traffic on the bridge.”

Some of these bridges are part of the 60 demonstration projects ISIS currently uses to convince the construction industry, which is conservative by its nature, to adopt these new technologies. Cultures though are slow to change, but they do change; in a 2005 impact survey, 90 percent of the 160 respondents said they would continue using ISIS technologies. To further this proliferation, ISIS produced nine education modules now used in the classrooms of 52 countries, and it has trained 650 students.

The ISIS logo appears on 2,500 technical papers (journal and conference), five patents and five international agreements. What really impresses outsiders, though, is the collaboration it leads — 150 researchers from 15 universities. At a conference in Zurich last summer Meier listened to four American colleagues marvel at ISIS’s ability to collaborate. “They were surprised,” Meier said. “But for me they confirmed what I observed 20 years ago.”

The ancient Egyptian goddess Isis was married to Osiris and they were held in special esteem. They brought civilization to mankind; they invented new crafts and they devised ways of practicing something useful and previously unknown. Whereas Meier studied cables, ISIS examined rebars. You see, the steel rods common inside concrete decks (the bridge part your tires touch) have incompatible flexibility compared to the concrete and this unharmonious marriage ultimately results in cracks, then corrosion, then costly repairs. A solution is to take the steel out of the deck and instead use it under the deck to connect the girders. This idea won Mufti the P.L. Pratley Award in 1993 for publishing the best paper on bridge design as judged by the Canadian Society for Civil Engineering.

He took the idea further and in 2007 again won the Pratley Award for suggesting a deck consist of nothing but glass fiber reinforced polymer (GFRP), which is light and 10 times stronger than steel. Since nothing in this bridge corrodes, mathematics suggests it could last for 100 years, far beyond the current 10 to 40 years.

When ISIS first proposed using GFRP rods as rebar, Meier was skeptical of the chemistry — alkali environments like concrete erode glass’ integrity. But after smothering GFRP in concrete and exposing it to the environment for nine years, they took a core sample and found the glass in excellent shape.

“There is no doubt ISIS is world-leading in this field now,” Meier said. “I would say they have been leaders for eight or ten years. And you know, it’s frustrating for me to say that because we were once number one.”

As the new experts on these materials it’s suiting that they received federal funding in August 2008 to act as a technical resource centre, helping others design and repair structures using FRPs and GFRPs.

But ISIS wants to act as more than just a resource centre. You see, if these new bridges consist of non-corroding materials, how do you spot a frail bridge? Sensors. ISIS coined the term “civionics” to refer to the sensors they developed to monitor a structure’s health.

The sensors come in two general forms: wired and wireless. The wired variety provides continuous information about the structure’s health and any ailment gets immediately noticed. It’s been likened to a traffic light. Without sensors, bridge inspections give either a green light (everything is fine), or a red light (the bridge failed, close it). The wired sensors provide that helpful amber — a warning of faults needing attention. And the wireless sensor, which Thomson studies, can, after cheap and easy installation, provide baseline data snapshots. Thomson likens them to a guitar. By strumming strings you can gauge the instrument’s condition. The same idea applies to these sensors, which detect displacement; when a bridge part moves, it alters the shape of the sensor, which affects its tone when it gets a pulse — an electromagnetic strum if you will. If a part of the bridge is out of whack, the “song” will tell.

Canada has limited records on the matter, but in the U.S. about 20,000 bridges are considered structurally deficient, meaning they cannot carry loads they were designed to. Of those 20,000, Thomson said only 40 are on the list because of testing. The rest are there because of visual inspection and calculations. But if you can test a bridge and confidently say its operating life is five years longer than assumed, that saves millions of dollars per bridge in unnecessary repairs.

“In the U.S. alone, if you use very conservative numbers, the value of putting sensors on bridges for service life extension is worth at least ten billion dollars, at least ten billion you’ll save in unnecessary repairs. That number is easy to support,” Thomson said. 

Nevertheless, sensors have not been widely adopted yet. Mufti, though, reckons this will change as ISIS graduates percolate through the field.

“I think the greatest legacy ISIS will leave behind will be the 650 highly qualified personnel because these people are ISIS children and they will start applying these ideas all throughout the engineering areas. And you couldn’t ask for a better outcome than that,” he said.

Within Canada, ISIS is a leader in monitoring. It already monitors structures around Manitoba and it has the expertise to provide this service nationally. Indeed, ISIS hopes its new role will be as a national centre for structural health monitoring. Just as British Columbia has TRIUM F, the national laboratory for nuclear and particle physics, and Alberta has the National Institute for Nanotechnology, one day, perhaps, Manitoba will have its own national centre based out of ISIS, one that monitors Canada’s infrastructure. And by watching a structure perform, not only do you save on repairs, but engineers can access data that allows them to improve designs and materials.

“Ideas never stop. You come up with an idea, implement it, and people improve. So ISIS started them but others have picked them up and taken them further,” Mufti said.

“No single person comes out with an idea that has never been done before. Lots of people think about it, but some do it in a way that makes them succeed.”