Magnetic Flux and Suspension Bridge Cables

Funny how sometimes two different things will cross your desk within a very short time but are actually linked to each other. Late on Sunday, evening after the family had all settled in, I jumped onto Google to look for the latest research being done using ANSYS (of course). I found an interesting paper titled “A Magnetic Flux Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables.” With infrastructure cost debates going on continually, I thought it would make for an interesting read. Turns out, our software was used to study the magnetic flux density of a suspension cable and the attraction between the transducer and the cable.

Then this morning, one of my U.S. colleagues pointed me to an article where the Pennsylvania Auditor General is calling for the passage of an infrastructure bill. Many of you may not know, but Pennsylvania has some of the worst bridges in North America. In fact, according the auditor general’s report, “Pennsylvania motorists are 10 times more likely to pass a structurally deficient bridge than a McDonald’s restaurant.” Either PA has a LOT of bridges or not many McDonald’s. I’ll assume the former, but I digress. Back to our infrastructure problems.

image of Structural Model of Suspension Bridge

The article also stated that, “According to the American Society of Civil Engineers, the U.S. needs to invest $2.2 trillion to repair highway, transit and water projects after years of neglect. In 2010 alone, the deficiencies in America’s roads, bridges, and transit systems cost U.S. households and businesses more than $129 billion.”

According to the paper, “The design life of these [suspension bridges, cable-stayed bridges and steel arch] bridges is about 100 years, however the design life of cables is often less than 30 years.” So what we have before us is not a small sum of money and it’s not a small task with over 110 suspension bridges in the United States alone.

Perhaps the solution is to just build new bridges, using new techniques to construct safer motorways for everyone. Bloomberg reports: Fiscal Games Can’t Hide True Cost of U.S. Roads.

While I don’t have the answer to these big questions, I do think that simulation engineering needs to be a big part of the discussion. By testing materials and experimenting with design in a virtual environment, engineers and designers can analyze safety, strength, comfort and environmental considerations. The result is cost-effective and innovative design. For insight into load capacity simulation you can download an article called “Bridging the Gap.”

I’ll leave you with one last thought. How important is simulation in the design of our bridges? Well, one of the most famous examples of really poor engineering is the Tacoma Narrows Bridge built in 1940.